JP2013168573A - Process of manufacturing supersonic thickness sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To significantly reduce cost of manufacturing a supersonic thickness sensor in a mass production scale by making it possible to collectively manufacture a number of supersonic thickness sensors which are capable of following, even when a surface to be measured is curved, and thin and exhibiting flexibility as a supersonic thickness sensor.SOLUTION: A number of segmented sinter raw material layers containing an oxide system piezoelectric material are segmented and formed at intervals on one plate surface of a metal thin plate that is to be a first electrode of a number of supersonic thickness sensors, the number of segmented sintered body layers are collectively formed at intervals on the metal thin plate by collectively heating and calcinating each of the segmented sinter raw material layers, a second electrode is formed on a surface of each of the segmented sintered body layers, a potential difference is provided between the other plate surface of the metal thin plate and surfaces of a number of the second electrodes, polarization treatment is performed for the segmented sintered body layer, the metal thin plate is cut in a thickness direction between adjacent segmented sintered body layers, and a number of supersonic sensors each having a single segmented sintered body layer are collectively and separately formed.

Description

  The present invention uses a piezoelectric element made of an oxide-based piezoelectric material to detect various thicknesses such as the thickness of metal pipes of various pipes, the wall thickness of other pipes, or the thickness of the outer wall of various metal containers by ultrasonic waves. The present invention relates to a method for manufacturing an ultrasonic thickness sensor.

2. Description of the Related Art As is well known, apparatuses that perform transmission / reception of ultrasonic waves using a piezoelectric element to detect various objects and target parts, perform various measurements, and diagnoses have been widely used. For example, sonar for underwater exploration, ultrasonic flaw detectors, and ultrasonic diagnostic apparatuses have been widely known. In addition, ultrasonic sensors are also used for thickness sensors that detect the thickness of metal plates and metal tubes. (For example, Patent Documents 1 and 2).
As a material of such a piezoelectric element for ultrasonic transmission / reception, an oxide-based piezoelectric material having a perovskite crystal structure represented by lead zirconate titanate (Pb (Zr, Ti) O ₃ ) called PZT ( Piezoelectric ceramics) is the most representative.

By the way, as a method of manufacturing a piezoelectric element made of this type of oxide-based piezoelectric material, a raw material powder such as PZT is formed into a predetermined bulk shape such as a disk shape or a cubic shape, and the formed body is sintered, and ceramic In general, a sintered body is formed, and then an electrode is attached to the sintered body, and then a polarization treatment is performed to form a piezoelectric element (see, for example, Patent Document 3).
Specifically, for example, in the case of a PZT piezoelectric element, first, raw material powder for PZT such as PbO, ZrO ₂ , TiO ₂ is blended at a predetermined ratio, and pure water is added to the blended powder and mixed and pulverized by a ball mill, It is dried and calcined, pulverized again to obtain a powder, further calcined and then pulverized again to obtain a PZT powder having a perovskite crystal structure. Then, a binder such as PVA (polyvinyl alcohol) is added to the PZT powder and mixed to obtain a granulated powder having an appropriate size. Thereafter, the granulated powder is molded by applying pressure to obtain a molded body having a predetermined bulk shape such as a thick disk shape or a cubic shape. Further, the molded body is heated to remove the binder, then heated to a high temperature and fired (sintered) to form a ceramic sintered body, and then processed into a predetermined product shape (piezoelectric element shape). Usually, an electrode such as a silver electrode is attached by baking or the like, and subjected to polarization treatment to impart piezoelectric characteristics.

  In the conventional method for manufacturing an oxide-based piezoelectric element as described above, it is known that the density of the sintered body is rapidly increased by raising the heating temperature at the time of sintering the molded body to about 1200 ° C. or higher. Therefore, sintering is generally performed at about 1200 to 1300 ° C. And it is known that the sintered body is densified to a density of 90% or more by firing at a high temperature of 1200 ° C. or higher, and a dense sintered body is obtained.

  As described above, the reason for increasing the density of the sintered body in the conventional manufacturing method is that the higher the density of the sensor element made of the sintered body, the higher the piezoelectric characteristics after the polarization treatment, and the more efficiently. It is possible to oscillate ultrasonic waves and easily increase the output of ultrasonic waves. Therefore, in the past, when manufacturing a piezoelectric element made of an oxide-based piezoelectric material, the sintering temperature is set to a high temperature of 1200 ° C. or higher so that the sintered body is densified to increase the piezoelectric characteristics as much as possible and to increase the output. Was common sense.

For example, in the case of ultrasonic sonar, the distance from the sensor to the detection target is remarkably large, and therefore a large output is required to reliably capture the target. In the case of ultrasonic flaw detectors, even if the distance to the site to be detected is short, the shape of the scratch or defect to be detected is not uniform, and the reflected wave from the scratch or defect is more It is necessary to discriminate between the received signals of the two kinds of reflected waves, that is, the reflected waves from the interface between the outer surface of the tube / external space existing at a distant position, and therefore, it is necessary to increase the output to some extent. Furthermore, in the case of an ultrasonic diagnostic apparatus, the shape of the region to be inspected is not uniform, and the attenuation of ultrasonic waves when passing through human tissue is large. Therefore, in these applications, the ceramic piezoelectric element is required to be as dense as possible. As for thickness sensors, it has been common knowledge to increase the density as in other applications.
If the output of the piezoelectric element is increased, the energy of the reflected wave increases accordingly. If the energy of the reflected wave is excessive, noise in the received signal of the reflected wave becomes large. Therefore, conventionally, when an excessive reflected wave is expected, a damper for attenuating the reflected wave is also incorporated.

By the way, in the conventional ultrasonic thickness sensor, every time it is necessary to measure the thickness, an ultrasonic medium such as water is applied to the front surface of the probe of the sensor and the outer surface of an object to be measured such as piping of various facilities. Usually, the thickness is measured by pressing and transmitting / receiving ultrasonic waves.
However, as for piping of various facilities, the outer surface of the metal pipe is often covered with a jacket such as a protective material or a heat insulating material. In such a case, when measuring the thickness of the pipe with the ultrasonic thickness sensor, it is necessary to prepare for removing the outer coating of the measurement location and applying or supplying the medium to the outer surface of the metal tube. Later, it is necessary to carry out a repairing work for wiping off the medium and further repairing the jacket. Therefore, the actual situation is that much work and time are required for one thickness measurement operation.

Further, in the conventional ultrasonic thickness sensor, whenever the thickness measurement is required as described above, the front surface of the sensor probe is placed on the outer surface of the measurement object via an ultrasonic medium such as water. Since it is usually pressed, it is difficult to measure the thickness of many places on the pipe and the outer wall of the container at the same time. Therefore, if you want to obtain thickness measurement data at many places, it takes a lot of time and effort. It was necessary to.
For the same reason, it has been difficult to continuously obtain measurement data of thickness over time.

On the other hand, since a piezoelectric element using an oxide-based piezoelectric material (ceramic piezoelectric material) obtained by a conventional manufacturing method has a dense sintered body and a thick bulk shape as a whole, it is flexible. Usually, it has no property (flexibility; flexibility). For this reason, when such a piezoelectric element is used in an ultrasonic thickness sensor for pipes, container outer walls, and the like, there are the following problems.
That is, among pipes, pipes having a small diameter, that is, pipe walls of pipes having a small radius of curvature on the outer surface, L-shaped bent portions or L-shaped welded portions of the piping, that is, elbow portions, When trying to measure the thickness of a curved part (convex or concave curved part) such as a corner of a T-shaped welded part, the front surface of the probe should be uniformly applied to the curved part. As a result, there is a problem that measurement error becomes large and thickness measurement becomes difficult.

Moreover, even if it is possible to manufacture an ultrasonic thickness sensor having flexibility by a conventional manufacturing method, that is, an ultrasonic thickness sensor capable of measuring the thickness of a curved portion such as a pipe,
The fact is that the technology has not been established to produce many of them on a mass production scale.

JP-A-1-202609 JP 2002-228431 A JP-A-7-45124

  The present invention has been made against the background of the above circumstances, and as an ultrasonic thickness sensor using an oxide-based piezoelectric material, it can be thin and flexible as a whole. By following the curved surface even if it is curved, it is possible to reliably measure the thickness on the curved surface, and by always sticking the thickness sensor to the measurement target part such as the pipe or the outer wall of the container This eliminates the need for preparatory work before thickness measurement and repair work after measurement, which can greatly reduce the time and effort involved in thickness measurement, as well as simultaneous thickness measurement at multiple locations and continuous measurement. A number of ultrasonic thickness sensors capable of accurate thickness measurement can be manufactured at the same time on a mass-production scale, thereby producing an ultrasonic thickness sensor capable of exhibiting flexibility as described above efficiently at a low cost. This And to provide a method to allow.

As described above, a piezoelectric element made of a conventional oxide piezoelectric material used for ultrasonic transmission / reception for various object detection, inspection, measurement, diagnosis and the like has a density of 90 in order to obtain high piezoelectric efficiency. It has been common knowledge to be dense so as to be equal to or higher than 50%, and an ultrasonic thickness sensor similarly uses a high-density piezoelectric element of 90% or higher.
However, the present inventors have found that high piezoelectric efficiency and high output as in other applications are not necessarily required for measuring the thickness of pipe walls and outer walls of containers in various facilities.

That is, as already described, in the case of an ultrasonic sonar for underwater exploration, an ultrasonic flaw detector, an ultrasonic diagnostic device, etc., the distance to the object is long, or the shape of the object is indefinite. High output is desired from the point that the attenuation until the ultrasonic wave reaches the target site is large, but in the case of thickness measurement of pipes and containers,
The thickness of the target tube wall and the outer wall of the container (distance to transmit / reflect the ultrasonic wave) is as small as several hundreds μm to a few dozen mm at the most, and the reflecting surface is a uniform fixed surface. It has been found that the thickness can be reliably measured even if the ultrasonic output is smaller than other applications because it is not necessary to distinguish the received signals of two or more kinds of reflected waves as in the case of ultrasonic flaw detection. . In other words, in the case of a thickness sensor, it has been found that even if the piezoelectric efficiency is lower than other applications, it can function sufficiently as a thickness sensor.

On the other hand, in a piezoelectric element made of an oxide-based piezoelectric material, if the density of the sintered body becomes low and becomes relatively porous, the piezoelectric efficiency decreases, but the thin flexible on the support body. If the sintered body layer is formed thin and porous, flexibility can be imparted. In that case, the support is also used as one of a pair of electrodes necessary for the piezoelectric element, and the support is allowed to function as one electrode even after the sintered body layer is formed on the support. Thus, it has been found that a thickness sensor can be manufactured by a simple process.
As described above, the thickness sensor can be made to have flexibility as a thickness sensor while reducing the density of the sintered body to some extent and simultaneously measuring thinning to slightly reduce the piezoelectric efficiency. Newly found.

Here, in order to form a thin sintered body layer on a thin support that also serves as an electrode as described above, a metal thin plate is used as the support, and a paste of the sintering raw material powder is applied to the metal thin plate. It is possible to apply and heat the whole support (metal thin plate) to fire the paste. In this case, following the above-described conventional method, if heated to a high temperature of about 1200 to 1300 ° C., excellent high temperature oxidation resistance that does not oxidize at a high temperature of 1200 to 1300 ° C. as a metal thin plate of an electrode and support. Platinum (Pt) or the like having a hydrogen content must be used. However, such a material having excellent high-temperature oxidation resistance such as platinum is usually extremely expensive, and in this case, the material cost of the thickness sensor becomes remarkably high.
However, when the present inventor repeated experiments and researches, ultrafine powder having an average particle size of 0.15 to 0.25 μm was used as the powder of the sintering material (piezoelectric material powder), or bismuth-based powder was used as the piezoelectric material powder. Mixing powder of low melting point glass such as glass, mixing alkoxide decomposition powder of metal constituting the piezoelectric material with piezoelectric material powder, and further, as piezoelectric material powder, If a paste kneaded with a metal alkoxide sol that constitutes the piezoelectric material is used, or a paste in which a piezoelectric material powder is dispersed in a sodium silicate solution is used, the temperature is about 600 to 800 ° C., which is much lower than conventional, or It has been found that sintering is possible even at lower temperatures. And if it is such a relatively low firing temperature, it becomes unnecessary to use expensive platinum or the like as the support that also serves as an electrode, and it is possible to use an inexpensive material such as stainless steel, Knowing that it is effective in reducing material costs, the present inventors have already filed patent applications for these technologies.

  By the way, when manufacturing an ultrasonic thickness sensor to be used by directly attaching to a pipe surface or the like by these techniques, for example, a small metal sheet of about 10 to 30 mm square made of thin SUS of about 15 to 150 μm ( Apply a paste or slurry containing an oxide-based piezoelectric material such as PZT as thin as about 150 μm to a planar area of about 5 to 15 mm square on the surface of one electrode), and dry the paste as necessary. After that, the piezoelectric piezoelectric material is heated to sinter, and the other electrode is thinly formed by applying and baking a silver paste on the surface of the sintered body layer. Processing is to be performed. However, in such a manufacturing process, the thickness of each material handled is as thin as several hundreds μm or less, and the overall planar size is as small as several centimeters or less. In order to manufacture a product, it is necessary to repeat the same operation many times. Therefore, the total manufacturing time has to be long and the manufacturing cost has to be high.

  Therefore, in the manufacturing method of the present invention, the handling of small and thin members at the time of manufacturing is reduced as much as possible, and at the same time, a large number of ultrasonic thickness sensors can be obtained at the same time. An ultrasonic thickness sensor can be manufactured.

  That is, in the method for manufacturing an ultrasonic thickness sensor of the present invention, basically, a number of segmented sintering raw material layers that are to be piezoelectric layers of the ultrasonic thickness sensor are respectively formed on the first electrodes of the multiple ultrasonic thickness sensors. Formed with a space on the surface of a sheet of metal sheet having a large area to be formed, and fired into a sintered sintered body layer after each of the sintered sintering raw material layers, each sectioned sintering A number of ultrasonic thickness sensors were manufactured at the same time by cutting a thin metal plate between body layers.

Specifically, the manufacturing method of the ultrasonic thickness sensor of the basic aspect (first aspect) of the present invention is:
A plurality of divided sintering raw material layers each made of a sintering raw material each containing an oxide-based piezoelectric material are divided at intervals on one plate surface of a thin metal plate to be the first electrode in a number of ultrasonic thickness sensors. A step of forming a divided sintered raw material layer to be formed;
The sintered raw materials are fired by heating each of the divided sintered raw material layers at once, whereby a plurality of divided sintered materials each comprising a sintered body of an oxide-based piezoelectric material having a density in the range of 70 to 80%. A firing step of forming a bonded layer on the plate surface at an interval;
A second electrode forming step of forming a second electrode on the surface of each sectioned sintered body layer,
A polarization treatment step of applying a potential difference between the other plate surface of the metal thin plate and the surfaces of a plurality of second electrodes to polarize the plurality of segmented sintered body layers;
After the polarization treatment, a separation step in which the metal thin plate is cut in the thickness direction between at least adjacent divided sintered body layers, and a plurality of ultrasonic sensors each having a sintered body layer are separately formed.
It is characterized by having.

In the manufacturing method of the ultrasonic thickness sensor according to the basic aspect of the present invention, a large number of thin metal plates to be used as one electrode (first electrode) in the ultrasonic thickness sensor are provided on the plate surface. A large number of segmented sintered material layers corresponding to each piezoelectric layer of the ultrasonic sensor are collectively formed, and further fired to form a plurality of segmented sintered material layers on the surface of one metal thin plate. Can be formed simultaneously. And finally, by dividing the metal thin plate, a large number of ultrasonic thickness sensors can be obtained simultaneously. Therefore, many ultrasonic thickness sensors can be manufactured in a significantly shorter time without repeating the same process many times compared to the case of manufacturing individual ultrasonic sensors.
In addition, since one metal thin plate functions as a support for a number of sectioned sintering raw material layers and a number of sectioned sintered body layers formed by firing the same, each ultrasonic thickness sensor is individually used as the metal sheet. Compared with the case of manufacturing, what has a remarkably large board area will be used. This means that the size of the intermediate product that is handled in each process until the metal sheet is finally cut is much larger than in the case of individually manufacturing the sensor, and therefore, during each process or between each process. Handling becomes easy.
In addition, since the metal thin plate functions as a support for supporting a number of segmented sintering raw material layers, even if the thickness of the segmented sintering raw material layer is reduced, it can be fired without any trouble in the firing process. In addition, the metal thin plate not only functions as an electrode, but also functions as a support for a sintered body layer (piezoelectric ceramic layer) even when a thickness sensor obtained by dividing the thin metal plate is used. Even if the density of the sintered body layer is as low as 70 to 80% and the thickness thereof is thin, the sintered body layer can be prevented from peeling off.
And if the metal thin plate as the first electrode is thin enough to show flexibility, and the second electrode is also sufficiently thin, the thickness of the thickness sensor is reduced, It can have flexibility. Furthermore, even if the sintered body layer has a relatively low density (70 to 80%), it can exhibit a piezoelectric property that does not interfere with the thickness sensor after the polarization treatment, and therefore a relatively low firing temperature (for example, 600 to 800). ° C, or 450 to 550 ° C) can be applied.
Further, by setting the density of the segmented sintered body layer (piezoelectric ceramic layer) to 80% or less, which is lower than that of the conventional general piezoelectric ceramic as described above, the sintered body layer of the first electrode is formed. Flexibility can be exhibited in a state where the metal thin plate is supported. At the same time, by setting the density of the sintered body layer to 70% or more, it is possible to ensure the necessary piezoelectric performance as an ultrasonic thickness sensor, and the sintered body layer becomes too low in density and becomes brittle. Thereby, it can prevent that a sintered compact layer peels from a 1st electrode.
In this specification, the density of the sintered body layer means a relative density.

  The ultrasonic thickness sensor manufacturing method according to the second aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to the first aspect, wherein a viscous liquid material containing an oxide-based piezoelectric material is used as the sintering material. In the sectioned sintering raw material layer forming step, forming each sectioned sintering raw material layer by adhering the viscous liquid material in a layered manner with a gap on one plate surface of the metal thin plate. It is a feature.

  And the manufacturing method of the ultrasonic thickness sensor of the 3rd aspect of this invention is the manufacturing method of the ultrasonic thickness sensor of the said 2nd aspect, and many 1st opening parts penetrated in the thickness direction are spaced apart. A first mask member to be formed is prepared in advance, and the first mask member is overlapped on one plate surface of the metal thin plate in the step of forming the divided sintering raw material layer. By applying the viscous liquid material on the surface side of the first mask member, the viscous liquid material is filled in each first opening of the first mask member, whereby a large number of the divided sintering raw material layers are formed in the metal thin plate. It is characterized by being formed with an interval on the plate surface.

  In the manufacturing method of the ultrasonic thickness sensor of the third aspect as described above, the first mask member having a large number of openings (first openings) is used, and the viscous liquid material as the sintering raw material is the first. By simply applying to the surface of the mask member, it is possible to simultaneously and easily form a large number of sectioned sintering raw material layers.

  The ultrasonic thickness sensor manufacturing method according to the fourth aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to the third aspect, wherein the second electrode formation is performed after the sintering raw material layer section forming step is completed. In the stage before the start of the process, the first mask member is removed from the one surface of the thin metal plate.

  In such a fourth aspect, even if heating is performed for forming the second electrode, the first mask member has already been removed at that stage, so that the first mask member is particularly heat resistant. There is no need to use a superior material, and the range of selection of the material for the first mask member is expanded.

  The ultrasonic thickness sensor manufacturing method according to the fifth aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to any one of the first to fourth aspects, wherein the ultrasonic thickness sensor penetrates in the thickness direction and each of the sections. A second mask member having a large number of second openings corresponding to at least a part of the surface of the sintered body layer is prepared in advance, and in the second electrode forming step, a second mask is formed. A member is stacked on the surface side of the plurality of sectioned sintered body layers, and in that state, a conductive paste is applied to the surface side of the second mask member, and the conductive paste is filled in each second opening and baked. Thus, the second electrode is formed on the surface of each sectioned sintered body layer.

  In such a fifth aspect, a second mask member having a large number of openings (second openings) is used, and a conductive paste for the second electrode is applied onto the second mask member. The second electrode can be simultaneously and easily formed on the surface of a large number of sectioned sintered body layers simply by baking.

  The ultrasonic thickness sensor manufacturing method according to the sixth aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to any one of the first to fifth aspects, wherein in the polarization treatment step, the thin metal plate is formed. The other plate surface and the surfaces of the second electrodes are sandwiched between a pair of polarization electrodes, and a potential difference is collectively applied between the metal thin plate and each of the second electrodes. The sectioned sintered body layer is polarized at once.

  In such a 6th aspect, since the many division | segmentation sintered compact layers are polarized at once, the efficiency of the polarization process in the case of manufacturing many ultrasonic thickness sensors can be improved.

  The ultrasonic thickness sensor manufacturing method according to the seventh aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to the second aspect, wherein the viscous liquid material containing the oxide-based piezoelectric material has an average particle diameter. Is a mixture (paste or slurry) of an oxide-based piezoelectric material powder in the range of 1 to 10 μm and an alkoxide sol of a metal component of the oxide-based piezoelectric material.

  In the manufacturing method of the ultrasonic thickness sensor of the seventh aspect, a viscous liquid containing an oxide piezoelectric material, that is, a relatively coarse powder (average particle diameter) made of an oxide piezoelectric material as a sintering raw material. 1 to 10 μm) and a paste or slurry obtained by mixing an alkoxide sol having the same metal component as the metal component of the oxide-based piezoelectric material. Therefore, in the firing step, a relatively low firing temperature (for example, Even at 600 to 800 ° C., it is possible to obtain a sintered body layer having a certain density (70 to 80%), that is, a piezoelectric characteristic that does not interfere with the ultrasonic thickness sensor after polarization treatment and at the same time exhibit flexibility. The resulting sintered body layer can be formed.

  The ultrasonic thickness sensor manufacturing method according to the eighth aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to the second aspect, wherein the viscous liquid material containing the oxide piezoelectric material has an average particle diameter. 1 to 10 μm oxide piezoelectric material powder and fine powder having an average particle size of 0.1 to 1.0 μm obtained by decomposition of alkoxide of metal component of oxide piezoelectric material dispersed in a dispersion medium (paste or slurry) ) Is used.

  Even in the method of manufacturing the ultrasonic thickness sensor of the eighth aspect, a viscous liquid material containing an oxide piezoelectric material, that is, a relatively coarse powder (average particle diameter) made of an oxide piezoelectric material as a sintering raw material. 1 to 10 μm) and a slurry or paste in which a mixture obtained by mixing a fine alkoxide-decomposed fine powder of the same metal component as the metal component of the oxide-based piezoelectric material is used. Similar to the embodiment, in the firing step, even at a relatively low firing temperature (for example, 600 to 800 ° C.), a sintered body layer having a certain density (70 to 80%), that is, an ultrasonic thickness sensor is not affected. Thus, it is possible to form a sintered body layer which can be obtained after the polarization treatment and can exhibit flexibility.

  The ultrasonic thickness sensor manufacturing method according to the ninth aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to the second aspect, wherein the oxide-based piezoelectric material is used as the viscous liquid material containing the oxide piezoelectric material. It is characterized in that a super fine powder made of a piezoelectric material having an average particle size of 0.15 to 0.25 μm is dispersed in a dispersion medium (slurry or paste).

  In the manufacturing method of the ultrasonic thickness sensor of the ninth aspect as described above, as a viscous liquid material containing an oxide-based piezoelectric material, that is, as a sintering raw material, an extremely fine ultra-fine particle having an average particle diameter of 0.15 to 0.25 μm. Since a slurry or paste in which fine powder is dispersed in a dispersion medium is used, in the firing step, as in the eighth or ninth aspect, even at a relatively low firing temperature (eg, 600 to 800 ° C.) to some extent. A sintered body layer having a density of 70 to 80%, that is, a sintered body layer capable of obtaining a piezoelectric characteristic after the polarization treatment, which is satisfactory for an ultrasonic thickness sensor, and exhibiting flexibility. be able to.

  And the manufacturing method of the ultrasonic thickness sensor according to the tenth aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to any one of the seventh to ninth aspects, wherein the heating temperature in the firing step is 600 to 600. It is characterized in that a segmented sintered body layer having a density in the range of 70 to 80% within a range of 800 ° C. is obtained.

  In the method of manufacturing the ultrasonic thickness sensor of the tenth aspect, the heating temperature in the firing step is set in the range of 600 to 800 ° C., which is much lower than the firing temperature in conventional general piezoelectric ceramic production. Sintering is advanced even by sintering at a low temperature to form a sectioned sintered body layer having a density (70 to 80% lower than that of the prior art) capable of exhibiting the piezoelectric characteristics necessary for an ultrasonic thickness sensor. be able to. In addition, the sintered body layer sintered to a relatively low density can exhibit flexibility in a state where the sintered body layer is supported by the metal thin plate of the first electrode, and On the other hand, it can also be prevented that the density of the sintered body layer becomes excessively small and the sintered body layer becomes brittle and peels from the first electrode.

  An ultrasonic thickness sensor manufacturing method according to an eleventh aspect of the present invention is the method for manufacturing an ultrasonic thickness sensor according to the second aspect, wherein the oxide piezoelectric material is used as the viscous liquid material containing the oxide piezoelectric material. A material powder (low-melting glass powder) dispersed in a dispersion medium (slurry or paste) is used.

  In the ultrasonic thickness sensor manufacturing method according to the eleventh aspect, a low-melting glass powder is mixed with an oxide piezoelectric material powder and dispersed in a dispersion medium as a viscous liquid material containing the oxide piezoelectric material. Since the slurry or paste is used, at least a part of the low melting point glass powder is melted or softened in the firing process to function as a binder between the piezoelectric material powder particles, and thereby the density of the piezoelectric material powder particles is relatively low. With the density (70 to 80%), the piezoelectric material powder particles are bonded. That is, since the low melting point glass forming material starts to melt or soften even at a relatively low temperature, the piezoelectric material powder particles are physically bonded even at a low firing temperature of about 450 to 550 ° C. As a result, a segmented sintered body layer in which the piezoelectric material powder particles are firmly bonded to some extent is obtained. And such a sintered compact layer can show the piezoelectric characteristic of the grade which does not have a trouble as an ultrasonic thickness sensor in polarization processing, and can show flexibility.

  The ultrasonic thickness sensor manufacturing method of the twelfth aspect of the present invention is characterized in that, in the ultrasonic thickness sensor manufacturing method of the eleventh aspect, the low melting point glass powder is a bismuth glass powder. To do.

  Since the bismuth-based glass powder used in the ultrasonic thickness sensor manufacturing method of the twelfth aspect is reliably and sufficiently melted at a firing temperature of 450 to 550 ° C., the binder between the particles of the piezoelectric material powder Can function reliably.

  The ultrasonic thickness sensor manufacturing method according to the thirteenth aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to the second aspect, wherein the oxide piezoelectric material is used as the viscous liquid material containing the oxide piezoelectric material. A material powder (slurry or paste) dispersed in a sodium silicate solution is used.

In the method of manufacturing the ultrasonic thickness sensor of the thirteenth aspect, sodium silicate, that is, sodium silicate (Na ₂ O · nSiO ₂ ) is solid when the viscous liquid (slurry or paste) as a sintering raw material is dried. A binder between the piezoelectric material powder particles, which precipitates between the particles of the oxide-based piezoelectric material powder (usually hydrate crystals), and at least part of the sodium silicate melts or softens during firing. Will function reliably. Therefore, as in the twelfth aspect, the piezoelectric material powder particles are physically bonded even at a low firing temperature of about 450 to 550 ° C., and as a result, the piezoelectric material powder particles remain at a relatively low density (70 to 80%). Can be obtained. And such a sintered compact layer can show the piezoelectric characteristic of the grade which does not have a trouble as an ultrasonic thickness sensor in polarization processing, and can show flexibility.

  The ultrasonic thickness sensor manufacturing method according to the fourteenth aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to any one of the eleventh to thirteenth aspects, wherein the heating temperature in the baking step is 450 to 550. A segmented sintered body layer having a density in the range of 70 to 80% within the range of ° C. is obtained.

  In the method of manufacturing the ultrasonic thickness sensor according to the fourteenth aspect, the heating temperature in the firing step is set in the range of 450 to 550 ° C., which is much lower than the firing temperature in conventional general piezoelectric ceramic production. Sintering is advanced even by sintering at a low temperature to form a sectioned sintered body layer having a density (70 to 80% lower than that of the prior art) capable of exhibiting the piezoelectric characteristics necessary for an ultrasonic thickness sensor. be able to. In addition, the sintered body layer sintered to a relatively low density can exhibit flexibility in a state where the sintered body layer is supported by the metal thin plate of the first electrode, and On the other hand, it can also be prevented that the density of the sintered body layer becomes excessively small and the sintered body layer becomes brittle and peels from the first electrode.

  The ultrasonic thickness sensor manufacturing method according to the fifteenth aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to any one of the first to fourteenth aspects, wherein the metal thin plate has a thickness of 10 to 150 μm. In addition, the layered sintered body layer is formed so that the thickness thereof is in the range of 30 to 150 μm, and the second electrode is formed in the range of 10 to 100 μm. It is formed so that it may become inside.

  According to such a fifteenth aspect, since the thickness of the sintered body layer is as thin as 30 to 150 μm, it exhibits flexibility in a state where the sintered body layer is supported by the first electrode. Furthermore, since the metal thin plate and the second electrode of the first electrode are also thin, the thickness sensor finally obtained can easily exhibit flexibility.

  The ultrasonic thickness sensor manufacturing method according to the sixteenth aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to any one of the first to fifteenth aspects, wherein the oxide-based piezoelectric material is a perovskite crystal. An oxide piezoelectric material having a structure is used.

  The ultrasonic thickness sensor manufacturing method according to the seventeenth aspect of the present invention is the method for manufacturing an ultrasonic thickness sensor according to the sixteenth aspect, wherein the lead-based zirconate titanate piezoelectric material is used as the oxide-based piezoelectric material. It is characterized by using a material.

  An ultrasonic thickness sensor manufacturing method according to an eighteenth aspect of the present invention is the ultrasonic thickness sensor manufacturing method according to any one of the first to seventeenth aspects, wherein a stainless steel thin plate is used as the first electrode. The method for manufacturing an ultrasonic thickness sensor according to any one of claims 1 to 18, wherein the ultrasonic thickness sensor is used.

According to the method for manufacturing an ultrasonic thickness sensor of the present invention, a large number of ultrasonic thickness sensors that are thin and flexible as a whole sensor can be manufactured simultaneously, so that the mass production scale. It is possible to manufacture an ultrasonic thickness sensor at a low cost by greatly reducing the time and labor required for making a large number of ultrasonic thickness sensors. Compared with the case where the sonic thickness sensor is manufactured individually, the size is much larger, so that the handling of the member during the manufacturing process or between the processes becomes easy.
In the method of the present invention, since the firing temperature can be made relatively low, it is not necessary to use an expensive material such as platinum, which is extremely excellent in high-temperature oxidation resistance, as an electrode material. it can. If the ultrasonic thickness sensor is thin and flexible as described above, even if the measurement target site is a curved surface, it can be deformed following the curved surface. Thickness measurement can be performed reliably. In addition, such a thickness sensor can be pasted on a measurement object such as a pipe in advance, and piping equipment etc. can be operated as it is, and the thickness can be measured whenever necessary. Pre- and post-operations, such as outer cover removal and medium coating before measurement, and medium wiping and outer cover repair after measurement, can be made unnecessary. In addition, thickness sensors can be attached to a number of locations to facilitate simultaneous measurement of thicknesses at a number of locations, as well as continuous and continuous thickness measurement. A remarkable effect can be obtained.

It is a flowchart which shows 1st Embodiment of the manufacturing method of the ultrasonic thickness sensor of this invention. It is a schematic diagram which shows an example of the division sintering raw material layer formation process in 1st Embodiment of the manufacturing method of the ultrasonic thickness sensor of this invention. It is a schematic diagram which shows an example of the 2nd electrode formation process in 1st Embodiment of the manufacturing method of the ultrasonic thickness sensor of this invention. It is a schematic diagram which shows an example of the polarization process process and isolation | separation process in 1st Embodiment of the manufacturing method of the ultrasonic thickness sensor of this invention. It is a schematic diagram which shows an example of the sintering raw material layer formation process in 2nd Embodiment of the manufacturing method of the ultrasonic thickness sensor of this invention. It is a schematic diagram which shows an example of the 2nd electrode formation process in 2nd Embodiment of the manufacturing method of the ultrasonic thickness sensor of this invention. It is a rough longitudinal cross-sectional view which shows an example of the ultrasonic thickness sensor obtained by the manufacturing method of this invention as the condition at the time of the use. It is a rough longitudinal cross-sectional view which shows the other example of the condition at the time of use of an example of the ultrasonic thickness sensor obtained by the manufacturing method of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 schematically shows an ultrasonic thickness sensor manufacturing method according to the first embodiment of the present invention.
In the first embodiment, an oxide piezoelectric material, for example, a viscous liquid containing PZT is used as a sintering raw material, and a mask member (first mask member) is used in the step of forming a divided sintering raw material layer. Further, a mask member (second mask member) is used also in the second electrode forming step, and a process of collectively polarizing is applied in the polarization treatment step. The manufacturing method of the first embodiment as described above basically includes:
P1: a preparation step (sintering raw material preparation step) for preparing a slurry or paste (herein collectively referred to as a viscous liquid material) as a sintering raw material containing a powder such as an oxide-based piezoelectric material, such as PZT,
P2: A metal thin plate to be a first electrode of a large number of ultrasonic thickness sensors and a first mask member having a large number of openings (first openings) are prepared in advance, and one of the metal thin plates is prepared. The first mask member is disposed on the plate surface, and the viscous liquid material is applied to the surface side of the first mask member, so that the viscous liquid material is filled in the respective openings, and thereby a plurality of sectioned sinterings are performed. A step of forming a raw material layer by forming a raw material layer at intervals on the one plate surface of the thin metal plate;
P3: The respective sintered material layers are collectively heated to sinter the sintered material, whereby a large number of divided sintered layers each made of a sintered body of an oxide-based piezoelectric material are formed on the plate surface. A baking process to form at intervals,
P4: A second mask member in which a large number of openings (second openings) are formed is prepared in advance, and the second mask member is overlaid on the surface side of a large number of sectioned sintered body layers. Then, the conductive paste is applied to the surface side of the second mask member, the conductive paste is filled in each opening, and baked to form the second electrode on the surface of each sectioned sintered body layer. Electrode formation process,
P5: A pair of electrodes for polarization treatment is sandwiched between the other plate surface of the metal thin plate and the surfaces of a large number of second electrodes, and a potential difference is collectively applied between the metal thin plate and each second electrode. A polarization treatment step for performing polarization treatment on the plurality of divided sintered body layers at once,
P6: a separation step in which the metal thin plate is cut in the thickness direction between adjacent sectioned sintered body layers, and a plurality of ultrasonic sensors each having a single sectioned sintered body layer are separated and formed in a lump.
An ultrasonic thickness sensor made of a ceramic piezoelectric material is manufactured by the process consisting of the above steps P1 to P6.
These steps P1 to P6 will be specifically described below.

[Preparation process (sintering raw material preparation process) P1]
First, as a preparation step, an oxide-based piezoelectric material made of a ferroelectric material having a perovskite crystal structure, for example, a paste containing slurry such as PZT or a viscous liquid such as slurry is prepared.
Here, as the powder for the oxide-based piezoelectric element, a powder made of particles having a predetermined component composition having a perovskite crystal structure, such as a PZT powder, is commercially available from a ceramic powder manufacturer or the like. In carrying out the manufacturing method of the ultrasonic thickness sensor, this type of commercially available ceramic piezoelectric element powder may be purchased and used as a starting material. However, it goes without saying that starting from the preparation of the raw material powder, the process for preparing the raw material powder will now be briefly described.

That is, an oxide powder as a raw material such as PZT, for example, each powder of PbO, ZrO ₂ and TiO ₂ is blended so as to have a target PZT composition, and a solvent such as ethanol and a dispersion medium such as polyethyleneimine are mixed. The kneaded material (slurry) obtained is kneaded with a ball mill or the like and dried to obtain a mixed powder. Further, the mixed powder is temporarily fired in a powder state. This pre-baking may be usually performed in an air atmosphere at a temperature of about 700 to 900 ° C. for about 1 to 20 hours. By such preliminary calcination, each component of the mixed powder (for example, PbO, ZrO ₂ , TiO ₂ ) is solid-solved with each other, and a perovskite crystal structure is obtained. If the obtained powder (however in the state after calcination) is pulverized by a ball mill or a bead mill, a powder for a ceramic piezoelectric material such as PZT can be obtained.

In the present invention, the type and composition of the target oxide-based piezoelectric material (ceramic piezoelectric material) are not basically limited, but are oxide-based piezoelectric materials made of a ferroelectric having a perovskite crystal structure. Among them, among them, lead zirconate titanate (Pb (Zr, Ti) O ₃ ) called PZT, more specifically, Pb (Zr _x Ti _1-x ) O ₃ [however, 0. 5 ≦ x ≦ 0.7], and more preferably PZT having a composition in which the value of x is about 0.52. In addition, on the basis of the PZT composition described above, one or more of Mn, Mg, Ca, Sr, Ba, V, Nb, Ta, La, Nd, Sc, Gd, and the like are added as trace elements. Each of them may be added in an amount of about 10% by weight or less. In short, all materials called PZT-based (lead zirconate titanate) piezoelectric ceramic materials are targeted. Furthermore, the piezoelectric ceramic material is not limited to the PZT-based piezoelectric ceramic material, and other piezoelectric ceramic materials having a perovskite crystal structure, such as LiNbO _3, and other piezoelectric ceramic materials having no perovskite crystal structure, such as Bi ₃ Ti ₄ O _12, etc. Can also be applied.

Typical examples of the viscous liquid material (slurry or paste) containing the oxide-based piezoelectric material represented by PZT as described above include the following A to E.
A: A mixture of an oxide-based piezoelectric material powder having an average particle diameter of 1 to 10 μm and an alkoxide sol of a metal component of the oxide-based piezoelectric material.
B: An oxide piezoelectric material powder having an average particle diameter of 1 to 10 μm and a fine powder having an average particle diameter of 0.1 to 1.0 μm by decomposition of an alkoxide of a metal component of the oxide piezoelectric material were dispersed in a dispersion medium. Slurry or paste.
C: A slurry or paste in which an ultrafine powder having an average particle diameter of 0.15 to 0.25 μm made of an oxide piezoelectric material is dispersed in a dispersion medium.
D: A slurry or paste in which an oxide piezoelectric material powder and a low-melting glass powder (typically bismuth glass powder) are dispersed in a dispersion medium.
E: Paste in which oxide-based piezoelectric material powder is dispersed in a sodium silicate solution.
In the method of this invention, you may prepare any viscous liquid substance of said A-E in a preparatory process. The method for preparing these viscous liquid materials and desirable conditions will be described in detail later.

[Section sintering raw material layer forming step P2]
An example of a specific implementation status of the sectioned sintering material layer forming step in the present embodiment is shown in FIG.
In carrying out this sectioned sintering raw material layer forming step, the metal thin plate 1 that will be the first electrode in a number of finally obtained ultrasonic thickness sensors is prepared in advance. The thin metal plate 1 is cut in a subsequent separation step, and each of the thin plates 1 becomes a first electrode in a number of ultrasonic thickness sensors. Therefore, the thin metal plate has an ultrasonic thickness to be finally obtained. Depending on the number of sensors, the first electrode has a total area or a larger area than that. In addition, a thin plate-like or sheet-like first mask member 3 in which a large number of first openings 5 penetrating in the thickness direction are dispersedly formed in the direction along the surface is prepared in advance. deep. Here, the number of the first openings 5 (the number of openings) is determined so as to correspond to the number of ultrasonic thickness sensors to be finally obtained. In the illustrated example, a large number of openings 5 are dispersed in the first mask member 3 in a two-dimensional direction, that is, dispersedly formed in a matrix, but in some cases, are arranged in a line in a straight line. You may form in a state. However, from the viewpoint of the efficiency of manufacturing a large number of ultrasonic thickness sensors at the same time, it is desirable to form them dispersed in a two-dimensional direction in a matrix as shown in the figure.

  In this step of forming the layered sintered material layer, as shown in the upper part of FIG. 2, the first mask member 3 is placed on one plate surface of the thin metal plate 1 and the oxide piezoelectric material as described above is used. A viscous liquid material (paste or slurry) made of a sintering raw material is applied from above the first mask member 3, and the openings 5 are filled with the viscous liquid material. Then, if necessary, the viscous liquid material is dried by natural drying or heat drying as necessary, and then the second mask member 3 is removed. As shown in the lower part of FIG. Then, the thin metal plate 1 is formed in a state of being dispersed in a matrix form at intervals in a two-dimensional direction along the surface.

  The thin metal sheet 1 not only functions as a first electrode in each ultrasonic thickness sensor of the final product, but also has a number of segmented sintering raw material layers and a number of segmented sintering during use as a firing process or thickness sensor. It functions as a support for physically supporting the body layer.

  The material of the metal thin plate 1 is not particularly limited. In the case of the present embodiment, the viscous liquid material containing the oxide piezoelectric material is used at a relatively low temperature (A to In the case of C, it can be fired at about 600 to 800 ° C., and in the case of D and E, about 450 to 550 ° C.), so that a general heat-resistant metal having oxidation resistance up to about 800 ° C. can be used. That is, it is not necessary to use an expensive metal that can withstand up to 1200 ° C. or more, such as platinum, and stainless steel or other general heat-resistant steel can be used as a metal thin plate that also serves as the first electrode. Specifically, SUS304 series austenitic stainless steel known as 18Cr-8Ni, 18Cr-12Ni-2.5Mo SUS316 series austenitic stainless steel, and 22Ni-12Cr SUH309 series austenitic heat resistant steel. Can be used. All of these can be obtained at a much lower price than platinum.

  The thickness of the metal thin plate 1 is preferably 15 μm to 100 μm. If the thickness is less than 15 μm, the strength is insufficient, which may hinder handling during the sensor manufacturing process, and may be deformed or damaged during use as a thickness sensor. On the other hand, if the thickness exceeds 100 μm, the flexibility of the thin metal plate is lost, and the flexibility of the thickness sensor as a whole is inferior. May be difficult to do.

  In addition, as means for applying the viscous liquid material (paste or slurry), it is applied in general application / printing, such as application using a roll coater, squeegee, or brush, or spraying the viscous liquid material. Coating / printing means can be arbitrarily applied.

  The material of the first mask member 3 is not particularly limited, and stainless steel (SUS) or resin similar to the metal thin plate 1 can be arbitrarily used. Further, the thickness of the first mask member 3 corresponds to the thickness of the viscous liquid material filled in each opening 5, that is, the thickness of each sectioned sintering raw material layer. What is necessary is just to set to thickness which can ensure 70-200 micrometers as stated.

After applying the viscous liquid material, it is usual to dry the viscous liquid material filled in the openings 5. Here, after drying, the film shrinks from the state before drying to a thickness of about ½ to ¼ before drying, but the thickness after drying (therefore, the stage immediately before the start of the firing step described later) (Thickness) in the range of 70 to 200 μm is desirable. If the thickness at the stage immediately before the start of the firing process is less than 70 μm, the thickness of the sectioned sintered body layer after firing is too thin, and when the sensor is bent, it may be peeled off from the metal thin plate as the first electrode. On the other hand, if the thickness at the stage immediately before the start of the firing process exceeds 200 μm, the thickness of the sectioned sintered body layer after firing becomes too thick. As a result, the sintered body layer has sufficient flexibility as described later. May be difficult to give.
And in order to ensure the thickness after drying in this way, you may repeat application | coating of a viscous liquid material in multiple times, and it may make it dry for every application | coating.
In addition, you may perform the drying after apply | coating a viscous liquid material on a metal thin plate at the initial stage of the heating for sintering in the following baking process here.

[Baking step P3]
Subsequently, in the state where the sectioned sintering raw material layer 7 is formed on the plate surface of the metal thin plate 1 to be a plurality of first electrodes as described above, the sectioned sintering raw material layer 7 is heated and fired, Each is a sectioned sintered body layer.
In this firing step, firing is performed so that the density of the fired state (piezoelectric material sintered body layer) is in the range of 70 to 80%.

Here, if the density of the sintered sintered body layer after firing becomes a high density exceeding 80%, the rigidity of the sintered body layer becomes high and the flexibility becomes inferior, and as a result, as a thickness sensor If the sensor is curved at the time of use, the sintered body layer may be peeled off from the metal thin plate as the first electrode or cracks may be generated. It becomes difficult to apply. At the same time, when fired to a high density exceeding 80%, the shrinkage during firing is large, and there is a strong risk of peeling from the metal thin plate (support) as the first electrode. It becomes difficult to obtain a segmented sintered body layer in close contact with the metal thin plate as the first electrode.
On the other hand, if the density of the sintered sintered body layer after firing is less than 70%, the porosity in the sintered body layer is too high and the particles inside the sintered body layer are not sufficiently bonded. Therefore, there is a possibility that the sintered body layer may be peeled off during handling in subsequent processes or when used as a sensor, and at the same time, the porosity inside the sintered body layer is increased and the thickness is increased. There is a possibility that sufficient piezoelectric characteristics as an ultrasonic sensor cannot be obtained for measurement.

  Therefore, the density of the sintered sintered body layer after firing is in the range of 70 to 80%, but in order to form a partitioned sintered body layer having such a density, the above-mentioned A to C as viscous liquids are used. In the case of using one, the firing temperature is preferably in the range of 600 to 800 ° C., and in the case of still using D and E, the firing temperature is preferably in the range of 450 to 550 ° C. As described above, even in a firing temperature lower than the firing temperature of a conventional general oxide-based piezoelectric material (ceramic piezoelectric material), in the case of this embodiment, the sintered body density sufficient for the ultrasonic thickness sensor is sufficiently obtained. Can be obtained.

Here, when the above-mentioned AC are used as the viscous liquid, the firing temperature is higher than 800 ° C., and when the above D and E are used as the viscous liquid, the firing temperature is 450. If the temperature is higher than ° C., the sintering reaction between the powder particles proceeds rapidly during firing, and it becomes difficult to obtain a sintered body layer having a density of 80% or less. On the other hand, the firing temperature is 450 ° C. when the firing temperature is a low temperature of less than 600 ° C. when the above-mentioned viscous liquid materials are used, and the D, E materials are used as the viscous liquid materials. If the temperature is lower than 1, the sintering reaction between the powder particles does not proceed sufficiently, and it becomes difficult to increase the density of the sintered body layer to 70% or more. The atmosphere during firing is preferably air (air). Further, although the firing time varies depending on the firing temperature, it is usually preferably 1 to 10 hours.
By such a firing process, a large number of segmented sintered body layers having a predetermined thickness and a predetermined density are formed in a matrix on one plate surface of the metal thin plate 1 to be the first electrode of a large number of sensors. It becomes a state.

[Second electrode formation step P4]
In this second electrode forming step, the second electrode as the counter electrode of the first electrode (metal thin plate) in many ultrasonic thickness sensors is used as the upper surface of the sectioned sintered body layer (metal thin plate as the first electrode). FIG. 3 schematically shows an example of the second electrode forming step in the present embodiment.

In carrying out the second electrode forming step, a thin plate or sheet shape in which a large number of second openings 13 penetrating in the thickness direction are dispersedly formed in a matrix at intervals in the two-dimensional direction of the surface. The second mask member 11 is prepared in advance. Here, the 2nd opening part 13 is normally defined so that each position may correspond to at least one part of the surface of each division | segmentation sintered compact layer 9. FIG. When the openings 5 of the first mask member 3 are linearly arranged, it is needless to say that the openings 13 of the second mask member 11 are also linearly arranged correspondingly. It is.
In the present embodiment, as shown in the upper part of FIG. 3, the second mask member 11 is divided into a number of piece-wise firings so that the opening 13 is opened at least at a part of the surface of each piece-like sintered body layer 9. It arrange | positions so that it may overlap with the surface side of the combined layer 9. Then, for example, a conductive metal powder paste for the second electrode such as silver (Ag), that is, a conductive paste is applied from the surface side of the second mask member 11 and baked. As shown, the second electrode 15 is formed on the surface of each sectioned sintered body layer 9. The second mask member 11 is usually removed before baking the conductive paste.

The thickness of the second electrode 15 is preferably 10 to 100 μm. If the thickness of the second electrode 15 exceeds 100 μm, the flexibility of the thickness sensor may be impaired. On the other hand, when the second electrode 15 is formed thinly to a thickness of less than 10 μm, the surface of the sintered body layer is locally uneven. In addition, the second electrode 15 may become discontinuous.
The material of the second mask member 11 is not particularly limited, and stainless steel (SUS), resin, or the like can be arbitrarily used as in the first mask member. Further, the thickness of the second mask member 11 may be set to such a thickness that 10 to 100 μm can be secured as described above as the thickness of the second electrode 15 after baking.

  In this way, as shown in the lower part of FIG. 3, a large number of ceramic piezoelectric materials are formed on one plate surface of a thin metal plate 1 that also serves as a support (a first electrode of a number of sensors). A laminated body in which the divided sintered body layers 9 are formed in a matrix at intervals and the second electrodes 15 are formed on the surface of each of the divided sintered body layers 9 is obtained. Here, the metal thin plate 1 and the second electrode 15 function as electrodes for applying a polarization voltage in the next polarization processing step, and at the same time, function as electrodes for transmitting and receiving ultrasonic waves when used as a thickness sensor. To do.

[Polarization process P5]
After that, as shown in the upper part of FIG. 4, a direct current or pulsed potential difference is applied between the thin metal plate (which becomes the first electrode) 1 and the second electrode 15 in the laminated body, thereby polarization treatment. I do.
That is, the other plate surface of the thin metal plate 1 and the surfaces of the multiple second electrodes 15 are collectively sandwiched by a pair of polarization processing electrodes 17A and 17B, and the thin metal plate 1 and each of A potential difference is collectively applied between the second electrode 15 and a large number of sectioned sintered body layers 9 are collectively polarized.
By performing the polarization treatment in this way, each of the divided sintered body layers 9 exhibits piezoelectric characteristics.

[Separation process P6]
After performing the polarization treatment as described above, as shown in the lower part of FIG. 4, the thin metal plate 1 is disposed in the thickness direction between the adjacent divided sintered body layers 9 by an arbitrary cutting means such as a shear cutting machine. A plurality of ultrasonic sensors 21 each having a single sectioned sintered body layer 9 are collectively formed separately.
In this way, a large number of ultrasonic thickness sensors can be manufactured simultaneously through a series of steps.

  In an actual ultrasonic sensor, it is necessary to attach lead wires for inputting / outputting voltage signals for ultrasonic measurement to the first electrode and the second electrode. Therefore, it is usual to attach a lead wire to each electrode using a conductive paste or the like after the polarization treatment or before the polarization treatment.

Next, a second embodiment of the present invention will be described with reference to FIGS.
In the second embodiment, a preparation step (sintering raw material preparation step) for preparing a viscous liquid material (paste or slurry) to be a sintering raw material is the same as that in the first embodiment.
Here, in the first embodiment, a large number of openings (first openings) 5 in the first mask member 3 are in one-to-one correspondence with the sintered body layer in the ultrasonic thickness sensor to be finally obtained. In order to correspond, the size, shape and number are determined in accordance with the planar size, shape and number of the sectioned sintered body layer. In the second embodiment, each size of the first mask member 3 is determined. The number of openings 5 in the first mask member 11 is finally set so that the openings 5 correspond to the sintered body layers of two or more ultrasonic thickness sensors, that is, N is an integer of 2 or more. The ratio to the number of ultrasonic thickness sensors to be obtained (the number of sintered body layers) is determined to be 1: N, and the size and shape of each opening 5 are also the final values of the ultrasonic thickness sensors to be obtained. It is determined so as to correspond to N sintered body layers.

  Specifically, each opening 5 of the first mask member 3 has each ultrasonic sensor so as to correspond to a plurality of (N: three in the illustrated example) divided sintered body layers of the ultrasonic sensor. In the same manner as in the first embodiment, the first mask member 3 is overlaid on the metal thin plate 1 and a viscous liquid material ( If the first mask member 3 is removed after applying a paste or slurry), filling each opening 5 with a viscous liquid material, and drying, then each of the three sintered bodies of the ultrasonic sensor is applied to each of the sintered body layers. A plurality of corresponding sectioned sintering raw material layers 7 are formed on the metal thin plate 1 at intervals. Further, by firing each of the divided sintered material layers 7, a plurality of divided sintered body layers 9 corresponding to the three sintered body layers of the final ultrasonic sensor are spaced on the metal thin plate 1. Will be formed. Then, in the second electrode forming step, by using the second mask member 11 similar to that used in the first embodiment, the conductive paste is applied and baked at three locations on the upper surface of each sectioned sintered body layer 9. The second electrode 15 is formed at an interval. Thereafter, after performing polarization treatment collectively in the same manner as in the first embodiment, as a separation step, the metal thin plate 1 and its plate surface are divided along the cutting lines P and Q indicated by chain lines in the lower part of FIG. If the sintered body layer 9 is divided, each ultrasonic sensor is obtained in a separated state.

  In the separation step described above, in the division at the cutting line P shown in FIG. 6, each of the divided sintered body layers 9 is divided into three at the same time as the thin metal plate 1 is divided. In the division by, only the metal thin plate 1 is divided within the interval between the adjacent sectioned sintered body layers 9, so that the first electrode (divided metal thin plate) of each ultrasonic thickness sensor after the division is divided. A region where the sintered body layer is not placed is left in the vicinity of both ends. In that case, a region where the sintered body layer is not placed can be used as a lead wire connecting portion for the first electrode. In addition, in this way, the region where the sintered body layer is not placed is left in the vicinity of both end portions of the first electrode (divided metal thin plate), so that the ultrasonic thickness sensor can be handled (applied to the object to be measured). Work).

  In each of the above embodiments, in the polarization treatment step, all the divided sintered body layers are polarized at once. However, depending on the case, 1 or 2 of all the divided sintered body layers may be used. The process of sequentially polarizing the sintered body layer may be repeated a plurality of times. For example, in the example shown in the lower part of FIG. 2, in one polarization process, the polarization processing electrodes are used for three sectioned sintered body layers 9 included in one row arranged in the direction from the upper left to the lower right. Even if it repeats the process of carrying out polarization processing at the same time, and then moving the thin metal plate 1 and simultaneously carrying out the polarization processing by sandwiching the three divided sintered body layers 9 in the next row with the electrodes for polarization processing Good.

FIG. 7 shows the ultrasonic thickness sensor manufactured by the method of the first or second embodiment as described above, and the situation at the time of use.
In FIG. 7, reference numeral 31 denotes a first electrode of the ultrasonic thickness sensor 21 (the metal thin plate 1 is divided), and a piezoelectric material sintered body layer is formed on one plate surface of the first electrode 31. 33 (for example, PZT piezoelectric ceramic layer; corresponding to the divided sintered body layer 9 before separation) 33 is formed, and the second electrode 15 is formed on the surface of the piezoelectric material sintered body layer 33. Lead wires 37A and 37B are drawn out from the first electrode 31 and the second electrode 15, respectively. The thickness sensor 21 configured as described above has an adhesive 43 or the like so that one surface of the first electrode 31 is in contact with the surface of a thickness measurement object 41 (such as a wall of a metal tube or an outer wall of a container). By using and sticking, the thickness of the measurement object can be measured at any time. As the adhesive 43 at this time, a silver paste, a glass paste, a platinum paste, a gold paste, or the like may be used.

The ultrasonic thickness sensor manufactured according to each embodiment of the present invention as described above is an extremely thin one having a three-layer structure of a first electrode, a sintered body layer, and a second electrode as a whole. Even when a jacket is provided on the outside of the pipe for protection or heat insulation, the pipe is bonded to the outer surface in advance during pipe assembly, and a jacket for protection or heat insulation of the pipe is provided from the outside of the thickness sensor. In this state, the piping equipment can be used as it is, and the thickness can be measured appropriately in the state as it is. In that case, it is not necessary to remove the outer covering before the thickness measurement or to repair the outer covering after the measurement, and to apply the ultrasonic medium to the surface of the object before the thickness measurement, and the ultrasonic wave after the measurement. The work of wiping off the medium is also unnecessary.
Further, since this ultrasonic thickness sensor is thin and flexible as a whole, even if the surface of the measurement object 41 is curved as shown in FIG. The ultrasonic thickness sensor 21 can be bonded along the surface to measure the thickness at the curved portion.

  Next, in each of the above-described embodiments, the preparation method and desirable conditions will be described for each of the viscous liquid materials A to E including the oxide-based piezoelectric material to be prepared in the preparation step (sintering raw material preparation step).

[A: Viscous liquid material obtained by mixing an oxide piezoelectric material powder having an average particle size of 1 to 10 μm and an alkoxide sol of a metal component of the oxide piezoelectric material]

An oxide-based piezoelectric material powder such as PZT having an average particle diameter in the range of 1 to 10 μm is obtained by pulverizing an oxide-based piezoelectric material powder lump such as a PZT powder lump with a ball mill or the like as described above. be able to.
Here, the particle diameter of the oxide-based piezoelectric material powder is set to an average particle diameter of 1 to 10 μm. This is the conventional general method, that is, the oxide powder of the metal component constituting the oxide-based piezoelectric material. This is because the raw material powder obtained by mixing and firing and mechanically pulverizing it is usually about 1 to 10 μm in average particle size. Here, it is difficult to make the average particle size of the raw material powder less than 1 μm from the viewpoint of pulverization efficiency. On the other hand, setting the average particle size of the raw material powder to more than 10 μm is problematic from the viewpoint of sintering properties.

On the other hand, along with the preparation of the above-described oxide-based piezoelectric material powder, an alkoxide sol of a metal component of an oxide-based piezoelectric material such as PZT is prepared. The alkoxide sol prepared here is represented by the general formula M (OR) _X, where the metal component alkoxide of the oxide used as the raw material of the oxide piezoelectric material is M, the metal component is R, and the alkyl group is R. It is a mixed sol of metal alkoxide. For example, in the case of PZT, since the metal component M is mainly composed of lead (Pb), zirconium (Zr), and titanium (Ti), each sol of lead alkoxide, zirconium alkoxide, and titanium alkoxide is prepared. On the other hand, the alkyl group R is not particularly limited, but methyl group, ethyl group, propyl group, isopropyl group, amyl group, hexyl group, cyclohexyl group, butyl group, isobutyl group, t-butyl group, s-butyl group, etc. are applied. can do. More specifically, in the case of PZT, as lead alkoxide, lead diisoproxide, lead dibutoxide, etc., as zirconium alkoxide, zirconium tetrabutoxide, zirconium tetrapropoxide, etc., as titanium alkoxide, titanium tetraisopropoxide, titanium, etc. Tetrapropoxide or the like is preferably used.

Further, in this case, it is desirable that the composition of each alkoxide sol is determined so that the proportion of the metal component is equal to the proportion of the metal component in the target oxide piezoelectric material. That is, in the case of PZT represented by the general formula Pb (Zr _x Ti _1-x ) O ₃ , the molar ratio of the metal components of each alkoxide is Pb: Zr: Ti = 1: x: 1-x. It is desirable to blend as such.
However, based on the PZT composition of Pb (Zr _x Ti _1-x ) O ₃ [where 0.5 ≦ x ≦ 0.7], and as a trace amount of added elements, Mn, Mg, Ca, Sr, Ba, V, When a PZT-based piezoelectric ceramic material to which one or more of Nb, Ta, La, Nd, Sc, Gd and the like are added is targeted, the alkoxide sol does not necessarily include even the alkoxides of these trace element metals. It is not necessary, and it is sufficient if it contains alkoxides of Pb, Zr and Ti which are the main components. Of course, depending on the case, a sol containing a metal alkoxide of these trace addition elements may be used.

  The method for obtaining the alkoxide sol as described above is not particularly limited, and may be according to a conventional method, for example, a method of dissolving each metal alkoxide in a solvent.

A relatively coarse powder (average particle diameter of 1 to 10 μm) made of an oxide piezoelectric material having a perovskite crystal structure as described above and an alkoxide sol having a metal component of the same oxide piezoelectric material are mixed with ethanol or When a suitable solvent such as butanol or ethyl acetate is mixed, kneaded and dried, the viscous liquid material (paste) of A as a sintering raw material is obtained.
The mixing ratio of the oxide-based piezoelectric material powder and the alkoxide sol is not particularly limited, but usually the molar ratio of the metal component in the alkoxide sol to the metal component in the raw material powder is compared with the same metal component. It is desirable to mix so that it may exist in the range of 0.2-1.0. When the above molar ratio is less than 0.2, the alkoxide sol is too little, and the decomposition product of the sol does not function sufficiently as a sintering aid in the firing step, and therefore, sintering at low temperature becomes difficult, If the molar ratio exceeds 1.0, there are too many alkoxide sols, and when firing on a metal thin plate that also serves as the first electrode, the relatively coarse raw material powder particles are not sufficiently bonded and sintered. The body layer becomes powdery and increases the risk of scattering or peeling off.

Viscous liquid material A (paste) obtained by mixing such a relatively coarse oxide-based piezoelectric material powder (average particle size of 1 to 10 μm) and an alkoxide sol having a metal component of the same oxide-based piezoelectric material is fired. In the process of heating and firing in the process, the alkoxide present between the particles of the coarse oxide-based piezoelectric material powder (average particle size of 1 to 10 μm) is decomposed to produce a decomposition product in the form of ultrafine powder. The decomposition product functions to sinter-bond particles of relatively coarse oxide-based piezoelectric material powder, that is, as a sintering aid. Moreover, since the decomposition product itself has a target oxide ceramic piezoelectric material composition such as PZT, it also functions to improve piezoelectric characteristics. Therefore, by mixing and baking the alkoxide sol with the relatively coarse raw material powder in this way, sintering proceeds at a relatively low temperature and the piezoelectric characteristics are improved.
In the firing step, it is preferable to set the heating temperature in the range of 600 to 800 ° C. as already described.

[B: Disperse oxide-based piezoelectric material powder having an average particle diameter of 1 to 10 μm and fine powder having an average particle diameter of 0.1 to 1.0 μm by decomposition of the metal component alkoxide of the oxide piezoelectric material in a dispersion medium. Viscous liquid (slurry or paste)]

  An oxide-based piezoelectric material powder such as PZT having an average particle diameter in the range of 1 to 10 μm is obtained by pulverizing an oxide-based piezoelectric material powder lump such as a PZT powder lump with a ball mill or the like as described above. be able to.

  Here, the particle diameter of the oxide-based piezoelectric material powder is set to an average particle diameter of 1 to 10 μm. This is the conventional general method, that is, the oxide powder of the metal component constituting the oxide-based piezoelectric material. This is because the raw material powder obtained by mixing and firing and mechanically pulverizing it is usually about 1 to 10 μm in average particle size. Here, it is difficult to make the average particle size of the raw material powder less than 1 μm from the viewpoint of pulverization efficiency. On the other hand, setting the average particle size of the raw material powder to more than 10 μm is problematic from the viewpoint of sintering properties.

On the other hand, fine powder (average particle diameter of about 0.1 to 1.0 μm) of an oxide piezoelectric material such as PZT is generated by the alkoxide decomposition method in parallel with the preparation of the above oxide piezoelectric material powder.
A specific method for producing a fine powder of an oxide-based piezoelectric material such as PZT by the alkoxide decomposition method may be the same as the conventionally known alkoxide decomposition method, and is not particularly limited. Can be obtained by hydrolyzing a mixed sol of an alkoxide of a metal component of an oxide-based piezoelectric material such as PZT, for example, by adding water. The alkoxide sol mentioned here may be the same as the alkoxide sol used in preparing the above-mentioned viscous liquid substance A, and the details thereof are omitted here.

  By hydrolyzing the alkoxide sol as described above, a fine powder (alkoxide-decomposed fine powder) having an average particle size of 0.1 to 1.0 μm made of an oxide piezoelectric material can be obtained. Here, it is difficult to reduce the average particle size of the alkoxide-decomposed fine powder to less than 0.1 μm by a general alkoxide decomposition method. The function of the binder cannot be expected.

  A relatively coarse raw material powder (average particle diameter of 1 to 10 μm) made of the oxide-based piezoelectric material as described above, and a fine raw material powder (average particle diameter of 0.1 to 10 μm) made of the same oxide-based piezoelectric material by alkoxide decomposition. 1.0 μm) is mixed, kneaded with an appropriate solvent such as ethanol or ethyl acetate, and dried to obtain a viscous liquid material B as a sintering raw material.

  The mixing ratio of the relatively coarse oxide-based piezoelectric material powder and the alkoxide-decomposed fine powder is not particularly limited, but usually the metal component in the oxide-based piezoelectric material powder is compared with the same metal component. It is desirable to mix so that the molar ratio of the metal component in the alkoxide-decomposed fine powder to be in the range of 0.2 to 1.0. If the above molar ratio is less than 0.2, the alkoxide-decomposed fine powder is too small, and the fine powder does not function sufficiently as a sintering aid in the firing step, making it difficult to sinter at low temperatures. If the molar ratio exceeds 1.0, there are too many alkoxide-decomposed fine powders, and when firing on a metal thin plate, the relatively coarse raw material powder particles are not sufficiently bonded, and the sintered body layer is powdered. The risk of becoming sticky, scattering or peeling off increases.

  When such a viscous liquid material B is used, in the firing step, alkoxide-decomposed fine powder (average particle size) existing between particles (average particle size 1 to 10 μm) of a relatively coarse oxide-based piezoelectric material powder. The diameter 0.1 to 1.0 μm) functions to sinter-bond particles of relatively coarse oxide-based piezoelectric material powder, that is, as a sintering aid. Moreover, since the fine powder itself has a target oxide ceramic piezoelectric material composition such as PZT, it also functions to improve piezoelectric characteristics. Therefore, by firing the viscous liquid material in which the alkoxide-decomposed fine powder is mixed with the relatively coarse oxide-based piezoelectric material powder in this way, sintering proceeds at a relatively low temperature and the piezoelectric characteristics are improved. In this case, the firing temperature is the same as that of the viscous liquid material A described above. It is desirable to set it within the range of 600-800 degreeC.

[C: Viscous liquid material (slurry or paste) in which an ultrafine powder having an average particle size of 0.15 to 0.25 μm made of an oxide-based piezoelectric material is dispersed in a dispersion medium]

The method for obtaining the ultrafine oxide piezoelectric material powder having an average particle diameter of 0.15 to 0.25 μm as described above is not particularly limited, but as described above, pulverization with a ball mill or the like. The comparatively coarse (average particle diameter of about 0.5 to 10 μm) powder such as PZT obtained by the above can be obtained by further pulverizing using a wet bead mill.
In wet bead mills, the raw material powder to be crushed and the beads of the pulverization medium are charged into a pulverization chamber together with a dispersion medium made of a liquid such as water, and the agitator (rotor for stirring) is rotated at a high speed at several thousand rpm to thereby produce the beads. Agitation is applied to give kinetic energy, and the moving beads make the powder ultrafine particles by friction, shearing, collision with the raw material powder. Here, spherical particles made of a hard substance having a diameter of about 0.1 mm to 1 mm, generally about 0.5 mm are used as beads for the grinding medium. Examples of the hard substance include ceramics, glass, and metal, but zirconia and zirconia reinforced alumina are usually preferable.
In addition, as a dispersion medium in the wet bead mill, alcohol such as ethanol, other hexane, and the like can be used in addition to water.

Here, if the average particle size of the ultrafine powder exceeds 0.25 μm, it is densified to a predetermined density (for example, 70 to 80%) at a relatively low firing temperature of 600 to 800 ° C. in the subsequent firing step. This may make it difficult to obtain the piezoelectric characteristics necessary for an ultrasonic thickness sensor. On the other hand, micronization until the average particle size is less than 0.15 μm not only hinders productivity and increases costs, but also causes a problem of aggregation.
The ultrafine powder thus obtained is in the form of a slurry dispersed in a dispersion medium. Depending on the type of the dispersion medium, the slurry may be used as a viscous liquid C applied to a metal sheet as it is. Usually, it is preferable to once dry to form a dry ultrafine powder, and then paste again.

In this step for pasting, the ultrafine powder having an average particle size of 0.15 to 0.25 μm obtained as described above is kneaded with a dispersion medium to obtain a viscosity suitable for paste application. It is set as the ultrafine powder paste which has.
Specifically, it may be kneaded with a dispersion medium using a known dispersing / kneading machine for fine powders. For example, a three-roll mill, that is, a dispersion / kneading using a rotation difference of three rolls. It is preferable to use a machine. In addition, the kind of dispersion medium used in particular is not specifically limited, Ethanol, butyl carbitol, PVB ethanol, etc. can be used. Moreover, it is preferable that the viscosity produced | generated at this pasting process is 1000-10000 mPa * s. If the viscosity of the paste is less than 1000 mPa · s, it becomes difficult to form the paste on the metal thin plate with a uniform thickness at the time of application. On the other hand, if it exceeds 10000 mPa · s, the viscosity is too high and smoothing such as leveling. May cause problems.

  A thin metal plate using a paste (viscous liquid C) obtained by kneading ultrafine powder made of oxide piezoelectric material powder with an average particle size of 0.15 to 0.25 μm together with a dispersion medium as described above as a sintering raw material Since the particles of the oxide-based piezoelectric material powder are remarkably fine in the step of applying and drying on and then heating and baking, the powder particles are bonded even at a low baking temperature of 600 to 800 ° C. A sintered body density (70 to 80%) exhibiting piezoelectric characteristics necessary for an ultrasonic thickness sensor can be sufficiently obtained.

[D: viscous liquid material (slurry or paste) in which oxide piezoelectric material powder and low melting glass powder (typically bismuth glass powder) are dispersed in a dispersion medium]

  Also in this case, as in the case of preparing the viscous liquid materials A and B, a powder having an average particle diameter of about 0.5 to 10 μm made of an oxide piezoelectric material such as PZT is prepared. The specific method is the same as already described.

On the other hand, a low melting glass powder such as bismuth (Bi) glass is prepared, and a piezoelectric material powder (a piezoelectric ceramic powder such as PZT) is mixed with a low melting glass powder and dispersed in an appropriate dispersion medium. A paste as a viscous liquid material D of a sintering raw material is prepared.
Here, as the low melting point glass, a glass having a softening point (softening start temperature) lower than 450 ° C. may be selected. In addition to the above bismuth glass, phosphate glass, borophosphate glass, vanadium borate system. Although glass such as alkali silicate glass and lead glass such as PbO—SiO ₂ —B ₂ O ₃ can be used, bismuth glass is most desirable.

Here, Bi ₂ O _3, which is an oxide of bismuth, does not vitrify alone, but other oxides (glass-forming oxides) such as SiO ₂ , B ₂ O ₃ , P ₂ O ₅ , Li ₂ O It is known that a glass having a low melting point can be formed by vitrification by combining with one or more selected from among these. Specific examples of the bismuth glass include Bi ₂ O ₃ —SiO ₂ glass, Bi ₂ O ₃ —Li ₂ O glass, and Bi ₂ O ₃ —B ₂ O ₃ glass.
The above Bi ₂ O ₃ —SiO ₂ glass is
_{xBi 2 O 3 · (100-} x) SiO 2
However, x = 35-65 mol%,
And Bi ₂ O ₃ —Li ₂ O glass is
_{xLi 2 O · (100-x} ) Bi 2 O 3
However, x = 20-40 mol% or 70-80 mol%,
Furthermore, Bi ₂ O ₃ —B ₂ O ₃ -based glass is
_{xBi 2 O 3 · (100-} x) B 2 O 3
However, x = 30-80 mol%,
It can be expressed. Any of these bismuth-based glasses has a softening point lower than 450 ° C., and can be suitably used as a low-melting glass to be mixed with an oxide-based piezoelectric material powder such as PZT in the present invention.
In any of the bismuth-based glasses, if necessary, as another oxide, one of PbO, ZnO, SrO, BaO, CuO, Al ₂ O ₃ , Fe ₂ O ₃ , MgO, CeO or You may contain 2 or more types.

The average particle size of the low melting point glass powder such as bismuth glass used here is 1.0.
Within the range of ˜20.0 μm is preferable. If the average particle size of the low melting point glass powder is less than 1 μm, the cost for making the powder fine will increase. On the other hand, if it exceeds 20.0 μm, the piezoelectric material particles such as PZT in the finally obtained sintered body layer There is a possibility that the glass phase intervening between them is too large and the piezoelectric properties after the polarization treatment are impaired.

  The blending ratio of the oxide piezoelectric material powder such as PZT and the low melting glass powder such as bismuth glass is such that the total of the piezoelectric material powder and the low melting glass powder is 100 parts by weight. It is desirable to mix in an amount of 15 to 25 parts by weight. If the low-melting glass powder is less than 15 parts by weight, the effect of physically bonding the particles of the piezoelectric material powder by the melt or softened material of the low-melting glass powder in the subsequent firing step cannot be sufficiently obtained. There is a possibility that the layer becomes brittle and peels off from the thin metal plate also serving as the first electrode. On the other hand, if the low melting point glass powder exceeds 25 parts by weight, the amount of the glass phase interposed between the piezoelectric material particles such as PZT in the finally obtained sintered body layer is too much, and the piezoelectric film after polarization treatment There is a risk of damage to properties.

  Furthermore, the dispersion medium for dispersing the piezoelectric material powder and the low-melting glass powder is not particularly limited, and an appropriate solvent or water such as butyl carbitol, ethanol, or ethyl acetate may be used. Further, the ratio of the dispersion medium to the piezoelectric material powder and the low-melting glass powder is not particularly limited, but the viscosity of the paste obtained by dispersing and kneading is 1000 to 20000 mPa as described in the first embodiment. -It is desirable to determine the ratio of the dispersion medium so as to be s.

The paste made by mixing the piezoelectric material powder such as PZT with the low melting point glass powder such as bismuth-based glass and dispersing and mixing it in the dispersion medium is applied as a viscous liquid material D of the sintering raw material on the thin metal plate. Then, after drying, it is subjected to a firing step.
In this firing step, it is preferable that the heating temperature is in the range of 450 to 550 ° C. In this case, powder particles of low-melting glass such as bismuth glass are interposed between the particles of oxide-based piezoelectric material powder in the sintering raw material, and the powder particles of low-melting glass have a temperature of 450 to 550 ° C. When heating in the region, melting or softening is started, and it functions as a binder between the oxide piezoelectric material powder particles, and the oxide piezoelectric material powder particles can be physically bonded to each other. Therefore, by firing in the temperature range of 450 to 550 ° C., it is possible to obtain a sintered body layer in which the oxide-based piezoelectric material powder particles are bonded to each other to some extent without increasing the density.

  Here, when the firing temperature is less than 450 ° C., the melting or softening of the low-melting glass powder particles during firing may be insufficient even when the low-melting glass powder is mixed. There is a possibility that it is difficult to sufficiently bond the piezoelectric material powder particles. On the other hand, if the firing temperature exceeds 550 ° C., a direct sintering reaction between the oxide-based piezoelectric material powder particles proceeds during firing, making it difficult to obtain a sintered body layer having a density of 80% or less. . Further, if the firing temperature exceeds 550 ° C. as described above, it is necessary to use a metal sheet having high heat resistance, so that the material selection range of the metal sheet may be narrowed, and the material cost may be increased. The firing temperature is particularly preferably within the range of 480 to 530 ° C, even within the range of 450 to 550 ° C.

[E: Viscous liquid material (paste) in which oxide-based piezoelectric material powder is dispersed in sodium silicate solution]

  In this case, an oxide-based piezoelectric material powder such as PZT having an average particle diameter of about 0.5 μm to 10 μm prepared in the same manner as described above is dispersed and mixed in a sodium silicate solution to obtain a viscous liquid material as a sintering raw material. (Paste) is prepared.

Here, sodium silicate (sodium silicate) is represented by the general formula [Na ₂ O · nSiO ₂ ] and is usually in the form of a hydrate at room temperature, ie, [Na ₂ O · nSiO ₂ · xH. ₂ O]. Here, the molar ratio n of SiO _{2 to} Na ₂ O can be continuously changed, and n = 1 Na ₂ O.SiO ₂ , that is, Na ₂ SiO ₃ is expressed as sodium metasilicate. It is called a solid (crystal) in a hydrated state at room temperature. Further, it is known that sodium silicate having a molar ratio n of 1.5 to 4 is a so-called water glass having a high viscosity when a low concentration aqueous solution is used.
In the case of the present invention, sodium silicate used in a sodium silicate solution in which an oxide piezoelectric material powder such as PZT is dispersed has a molar ratio n of about 0.5 to 1.5. Although it is desirable to use sodium silicate, it is not so limited.

In addition, in dispersing and mixing an oxide-based piezoelectric material powder such as PZT in a sodium silicate solution, the sodium silicate (Na ₂ O · nSiO ₂ ) content in the sodium silicate solution is 100 parts by weight of the piezoelectric material powder. It is desirable that the amount be 20 to 40 parts by weight, preferably 25 to 35 parts by weight. If the sodium silicate content is less than 20 parts by weight, it may be difficult to firmly bond the oxide-based piezoelectric material powder particles during firing at a low temperature (450 to 550 ° C.), whereas if it exceeds 40 parts by weight. However, the proportion of the piezoelectric material powder is relatively small, which adversely affects the piezoelectric characteristics after the firing and polarization treatment, and there is a possibility that the piezoelectric characteristics necessary for the ultrasonic film thickness sensor cannot be obtained.

The concentration of the sodium silicate solution in which the piezoelectric material powder such as PZT is dispersed is appropriately determined from the viewpoint of ease of pasting and easy attachment to the surface of the metal thin film serving as the first electrode (applicability, printability). Just do it. That is, if the concentration of the sodium silicate solution is too low, it becomes difficult to form a paste layer with a certain thickness on the surface of the metal thin plate, whereas if the concentration of the sodium silicate solution is too high, the piezoelectric material powder such as PZT is uniformly dispersed. It becomes difficult to make it. Therefore, normally, the concentration of the sodium silicate solution is preferably in the range of 5 to 20 wt%.
Moreover, it is preferable that the viscosity of this paste is 1000-10000 mPa * s. If the viscosity of the paste is less than 1000 mPa · s, it becomes difficult to form the paste on the thin metal plate with a uniform thickness. On the other hand, if the viscosity exceeds 20000 mPa · s, the viscosity is too high, causing problems in smoothing such as leveling. There is a fear.

  The paste obtained by dispersing and mixing the oxide-based piezoelectric material powder such as PZT in the sodium silicate solution is applied onto the metal thin plate as a viscous liquid material E as a sintering raw material, dried, and then subjected to the next firing. Provided to the process.

Here, when the above paste (viscous liquid E) is dried on the surface of the metal thin plate, the sodium silicate crystals in the sodium silicate solution become piezoelectric material powder particles such as PZT as the moisture of the sodium silicate solution disappears. It precipitates between. That is, a fine powder composed of precipitated crystals of sodium silicate is interposed in the space between adjacent oxide-based piezoelectric material powder particles. At this time, the precipitation form of sodium silicate varies depending on the molar ratio n of SiO _{2 to} Na ₂ O in the sodium silicate used, but when n is near 1 (ie, near the sodium metasilicate composition), hydration It becomes a thing _{(Na 2 O · nSiO 2 ·} xH 2 O) crystals usually.

  Moreover, in a baking process, it is preferable to make heating temperature into the range of 450-550 degreeC. Such a temperature range of 450 to 550 ° C. is much lower than the firing temperature (about 1200 ° C.) of a conventional piezoelectric material powder such as PZT, but when a viscous liquid E is used, a sodium silicate solution The crystal fine powder of sodium silicate hydrate is precipitated between the particles of the piezoelectric material powder in the sintering raw material, and a part of the crystal fine powder of sodium silicate hydrate is 450 to 550. Starts melting or softening when heated in the temperature range of ℃, and it functions as a binder between the oxide-based piezoelectric material powder particles to physically bond the oxide-based piezoelectric material powder particles to each other Can do. Therefore, by firing in the temperature range of 450 to 550 ° C., the density of the piezoelectric material powder particles is firmly bonded to a certain degree without increasing the density so much (that is, in a relatively low density state of 70 to 80%). A sintered body layer can be obtained.

  Here, when the firing temperature is less than 450 ° C., even when sodium silicate is used, the melting or softening of the crystal fine powder of sodium silicate hydrate at the time of firing becomes insufficient. It may be difficult to bond to the. On the other hand, if the firing temperature exceeds 550 ° C., a direct sintering reaction between the oxide-based piezoelectric material powder particles proceeds during firing, making it difficult to obtain a sintered body layer having a density of 80% or less. . Further, if the firing temperature exceeds 550 ° C. in this way, it becomes necessary to use a metal sheet having high heat resistance as the first electrode, and the material selection range of the metal sheet is narrowed. May increase. The firing temperature is particularly preferably within the range of 480 to 530 ° C, even within the range of 450 to 550 ° C.

  Examples of the present invention will be described below.

This Example 1 uses a slurry of a mixture of a PZT powder as an oxide-based piezoelectric material powder and an alkoxide sol of a metal component of PZT as the viscous liquid material A of a sintering raw material, and has 200 ultrasonic thicknesses. It is the Example which manufactured the sensor simultaneously.
That is, first, powders of lead oxide (PbO), titanium oxide (TiO ₂ ), and zirconium oxide (ZrO ₂ ) were prepared as raw material powders for PZT, and these were prepared as PbO: 1 mol, ZrO ₂ : 0.5 mol. TiO ₂ : blended at a ratio of 0.5 mol, the solvent was ethanol, the dispersant was polyethyleneimine, and wet kneaded for 24 hours with a ball mill to obtain a slurry. The slurry is dried to form a mixed powder lump, which is then placed in an alumina crucible, covered with alumina, and subjected to heat treatment (temporary firing) at 850 ° C. for 10 hours to obtain a PZT powder lump having a perovskite crystal structure. It was. The PZT powder mass is pulverized, put through a 300 micron sieve into a ball mill, and pulverized in ethanol using zirconia balls as a pulverization medium for 24 hours to obtain a PZT powder having an average particle size of 2 μm and dried. It was.

  On the other hand, lead diisoproxide is prepared as lead alkoxide, zirconium tetrabutoxide is prepared as zirconium alkoxide, and titanium tetraisopropoxide is prepared as titanium alkoxide, and these have a molar ratio of Pb: Zr: Ti = 1: 0.5: 0.5. The alkoxide sol is mixed with xylene, and the alkoxide sol is mixed with the PZT powder having an average particle diameter of 2 μm and kneaded by a ball mill to obtain an alkoxide sol-PZT mixed dispersion (slurry viscous liquid A). It was.

  As a first mask member, a 20 cm × 20 cm square thin plate made of SUS304 and having a thickness of 100 μm was prepared. A total of 200 openings of 8 mm × 8 mm square were formed on the first mask member thin plate in a matrix at intervals. The interval between adjacent openings is 2 mm in a direction parallel to one side of the square of the first mask member thin plate, so that 20 openings are arranged in that direction, and on that side. In the orthogonal direction, it was set to 16 mm, and 10 openings were arranged in that direction.

  The first mask member is placed on one plate surface of a 25 μm-thick metal thin plate (20 cm × 20 cm square shape) made of SUS304 that will eventually become the first electrodes of the 200 ultrasonic thickness sensors. Superimposed. Then, the aforementioned alkoxide sol-PZT mixed dispersion (slurry) was applied onto the plate surface of the first mask member by air spray, the slurry was filled into each opening, and dried by natural drying. In practice, this operation was repeated several times so that the thickness after drying was 100 μm.

  After that, the first mask member is removed, and the divided sintering raw material layers are dispersedly formed in a total of 200 locations in a matrix at intervals of 2 mm or 16 mm on the metal thin plate to be the first electrode. It was in a state.

  Next, as a firing step, the sectioned sintered material layer was baked by performing a heat treatment at 700 ° C. Specifically, it was put into an electric furnace, heated to 700 ° C. at a heating rate of 2 ° C./min in an air atmosphere, held at 700 ° C. for 1 hour, and then the furnace age was given. As a result, on the plate surface of the thin metal plate made of SUS304, a sintered sintered body layer made of fired PZT having a thickness of 60 μm was baked at a total of 200 locations at intervals.

On the other hand, as a second mask member, a 20 cm × 20 cm square thin plate made of SUS304 and having a thickness of 50 μm was prepared. In this second mask member thin plate, a total of 200 5 mm round openings are formed in advance at positions corresponding to the centers of the respective divided sintered body layers. Overlaid on the upper surface side. Then, a silver paste for the second electrode is applied to the surface of the second mask member using a squeegee, and the silver paste is filled in each opening, and then baked at 500 ° C., and the surface of each sectioned sintered body layer A second electrode (silver electrode) having an average thickness of 20 μm was formed.
In this way, the divided sintered body layers made of PZT sintered bodies are respectively formed in a matrix at 200 locations on the surface of the metal made of SUS304 to be the first electrodes of 200 ultrasonic thickness sensors. A laminate was obtained in which a silver electrode as a second electrode was formed on the surface of the sectioned sintered body layer. The density of each sintered body layer was about 75%.

Next, the entire laminate was sandwiched between a pair of electrodes for polarization treatment each made of SUS304, and polarization treatment for applying a DC voltage of 300 V was performed for 1 minute.
Thereafter, the metal thin plate is divided into a size of 1 cm × 2 cm so that each includes one sectioned sintered body layer, and further a first electrode (metal thin plate after division) and a second electrode (silver). A total of 200 ultrasonic thickness sensors were obtained by bonding a lead wire to each of them with a conductive paste.

  When the polarization state (piezoelectric constant d33) was examined for each ultrasonic thickness sensor using a d33 meter, it was confirmed that all were polarized well. In addition, as an ultrasonic thickness sensor, the thickness of the tube wall was measured by attaching it to a tube wall of a stainless steel tube having an outer diameter of 10 cm and a wall thickness of 8 mm using a silver paste as an adhesive. It was confirmed that it worked well and the thickness was measured correctly.

  In Example 2, a mixture of a relatively coarse PZT powder produced by an oxide raw material mixing heating method and a PZT fine powder produced by an alkoxide decomposition method is used as the viscous liquid material B of the sintering raw material. This is an example in which 200 ultrasonic thickness sensors were manufactured at the same time by using the paste dispersed in.

  That is, first, PZT fine powder was prepared by an alkoxide decomposition method. Specifically, lead diisoproxide is prepared as lead alkoxide, zirconium tetrabutoxide is prepared as zirconium alkoxide, and titanium tetraisopropoxide is prepared as titanium alkoxide, and these are in a ratio of Pb: Zr: Ti = 1: 0.5: 0.5. The resulting mixture was hydrolyzed by adding water at 50 ° C. to obtain an alkoxide-decomposed PZT fine powder having an average particle size of 0.15 μm.

On the other hand, lead oxide (PbO), titanium oxide (TiO ₂ ), and zirconium oxide (ZrO ₂ ) powders are prepared as raw material powders for relatively coarse PZT powder, and these are prepared as PbO: 1 mol, ZrO ₂ : 0.5 mol, TiO ₂ : 0.5 mol was blended, the solvent was ethanol, the dispersant was polyethyleneimine, and wet kneaded for 24 hours with a ball mill to obtain a slurry. The slurry is dried to form a mixed powder lump, which is then placed in an alumina crucible, covered with alumina, and subjected to heat treatment (temporary firing) at 850 ° C. for 10 hours to obtain a PZT powder lump having a perovskite crystal structure. It was. The PZT powder mass is pulverized, put through a 300 micron sieve into a ball mill, and pulverized in ethanol using zirconia balls as a pulverization medium for 24 hours to obtain a PZT powder having an average particle size of 2 μm and dried. It was.

  The alkoxide-decomposed PZT fine powder having an average particle size of 0.15 μm and the PZT powder having an average particle size of 2 μm obtained as described above were compared with the same metal component. The powder was mixed at a ratio of 0.3 mol, and butyl carbitol was added as a dispersion medium (solvent) and kneaded to obtain a paste (viscous liquid B).

  Also, as the first mask member, a rectangular thin plate (opening number 200) made of SUS304 having an opening similar to that of the first embodiment is prepared, and also as a metal thin plate to be the first electrode. A SUS304 product similar to that of the first example is prepared, and the paste (viscous liquid material B) is applied onto the first mask member using a squeegee, overlaid in the same manner as in Example 1, Each opening of one mask was filled with paste and allowed to dry naturally, and then the first mask member was removed to form a state in which the divided sintered raw material layers were dispersedly formed at a total of 200 locations. Then, it heated and baked similarly to Example 1, and each division sintering raw material layer was used as the division sintered compact layer of PZT. Furthermore, using the same 2nd mask member as Example 1, a 2nd electrode is formed on each division | segmentation sintered compact layer by application | coating and baking of a silver paste, About Example 1 and In the same manner, a collective polarization process was performed, and then 200 pieces were separated and cut, and then lead wires were attached to obtain 200 ultrasonic thickness sensors.

  As for each ultrasonic thickness sensor after the polarization treatment, the polarization state was examined using a d33 meter. As a result, it was confirmed that the polarization was satisfactorily polarized, and the ultrasonic thickness sensor was actually made of stainless steel with an outer diameter of 10 cm. When the thickness of the tube wall was measured by adhering it to the tube wall of a tube having a thickness of 8 mm using a gold paste as an adhesive, it was confirmed that the tube worked well and the thickness was measured correctly.

  This Example 3 uses a paste in which an ultrafine powder having an average particle size of 0.15 to 0.25 μm made of an oxide piezoelectric material is dispersed in a dispersion medium as the viscous liquid C as a raw material for sintering. This is an example in which 200 ultrasonic thickness sensors were manufactured at the same time.

That is, as a raw material powder for PZT, lead oxide (PbO), titanium oxide (TiO ₂ ), and zirconium oxide (ZrO ₂ ) powders are prepared, and these are prepared as PbO: 1 mol, ZrO ₂ : 0.5 mol, TiO ₂ : blended at a ratio of 0.5 mol, kneaded with a ball mill using a solvent as ethanol and a dispersant as polyethyleneimine, and dried to obtain a mixed powder lump. The mixed powder lump was placed in an alumina crucible and heated (pre-baked) at 850 ° C. for 10 hours with the alumina covered, to obtain PZT powder having a perovskite crystal structure.
After coarsely pulverizing the PZT powder, a powder having an average particle size of 2.2 μm was obtained using a ball mill. Next, the powder was pulverized to a mean particle size of 0.2 μm using a wet bead mill. Note that zirconia having a particle diameter of 0.5 mm was used as beads (grinding medium) in the wet bead mill, and water was used as the dispersion medium.
The obtained ultrafine powder slurry was dried to obtain PZT ultrafine powder having an average particle size of 0.2 μm.
By adding butyl carbitol as a dispersion medium to the PZT ultrafine powder and kneading with a three roll mill, an ultrafine powder paste (viscous liquid C) was obtained.

  Also, as the first mask member, a rectangular thin plate (opening number 200) made of SUS304 having an opening similar to that of the first embodiment is prepared, and also as a metal thin plate to be the first electrode. A SUS304 product similar to that of the first embodiment is prepared, and the paste (viscous liquid C) is applied onto the first mask member using a squeegee, and stacked in the same manner as in the first embodiment. After filling each opening of 1 mask with paste and drying with warm air (40 ° C. air blowing), the first mask member is removed, and the divided sintered raw material layers are dispersedly formed at a total of 200 locations. It was in the state. Then, it heated and baked similarly to Example 1, and each division sintering raw material layer was used as the division sintered compact layer of PZT. Further, a second mask member similar to that in Example 1 is overlaid, a silver paste is applied with a squeegee, and baked to form a second electrode on each sectioned sintered body layer. In the same manner as in No. 1, a collective polarization process was performed, and then 200 pieces were separated and cut, and then lead wires were attached to obtain 200 ultrasonic thickness sensors.

  As for each ultrasonic thickness sensor after the polarization treatment, the polarization state was examined using a d33 meter. As a result, it was confirmed that the polarization was satisfactorily polarized, and the ultrasonic thickness sensor was actually made of stainless steel with an outer diameter of 10 cm. When the thickness of the tube wall was measured by adhering it to the tube wall of a tube having a thickness of 8 mm using a gold paste as an adhesive, it was confirmed that the tube worked well and the thickness was measured correctly.

  In this Example 4, as the viscous liquid material D of the sintering raw material, 200 pieces of oxide piezoelectric material powder and a paste in which bismuth glass powder as low melting point glass powder was dispersed in a dispersion medium were used. It is the Example which manufactured the ultrasonic thickness sensor simultaneously.

That is, first, as an oxide-based piezoelectric material powder, a PZT powder having an average particle size of 2.2 μm was prepared in the same manner as in Example 1, and the PZT powder was mixed with a bismuth-based glass powder having an average particle size of 2.5 μm. At the same time, a butyl carbitol solvent was added as a dispersion medium and kneaded by a roll mill to prepare a paste (viscous liquid D) as a sintering raw material. Here, as the bismuth-based glass powder, Bi ₂ O ₃ —SiO ₂ -based glass, that is, xBi ₂ O _3. (100-x) SiO ₂ with x = 50 mol% was used. The blending ratio of the PZT powder and the bismuth glass powder was 20 parts by weight of the bismuth glass powder with respect to 80 parts by weight of the PZT powder. The obtained paste had a viscosity of 2000 mPa · s.

Further, as the first mask member, a rectangular thin plate (200 openings) made of SUS304 having the same opening as in Example 1 is prepared, and as a metal thin plate to be the first electrode, a 50 μm thick SUS316 made of SUS316 is prepared. Prepare a paste and apply the paste (viscous liquid D) onto the first mask member using a squeegee, and fill each opening of the first mask with the same paste as in Example 1. Then, after drying with warm air (air at 40 ° C. was blown), the first mask member was removed, and the divided sintered raw material layers were dispersedly formed at a total of 200 locations.
Then, it put into the electric furnace, heated to 500 degreeC with the temperature increase rate of 500 degreeC / hr in the air atmosphere, and hold | maintained at 500 degreeC for 1 hour, it fired, and the furnace age was carried out. Thereby, what obtained by baking the 50-micrometer-thick division | segmentation sintered compact layer which mainly made the fired PZT in the total 200 places on the metal thin plate which should become a 1st electrode was obtained.

  Furthermore, using the same 2nd mask member as Example 1, the 2nd electrode was formed on each division | segmentation sintered compact layer by application | coating and baking (however, baking temperature is 300 degreeC) of silver paste, and obtained. The laminated body was subjected to collective polarization treatment in the same manner as in Example 1, and then separated and cut into 200 pieces, and then lead wires were attached to obtain 200 ultrasonic thickness sensors.

  As for each ultrasonic thickness sensor after the polarization treatment, the polarization state was examined using a d33 meter. As a result, it was confirmed that the polarization was satisfactorily polarized, and the ultrasonic thickness sensor was actually made of stainless steel with an outer diameter of 10 cm. When the thickness of the tube wall was measured by adhering it to the tube wall of a tube having a thickness of 8 mm using a gold paste as an adhesive, it was confirmed that the tube worked well and the thickness was measured correctly.

  This Example 5 is an example in which 200 ultrasonic thickness sensors were manufactured at the same time by using a paste in which an oxide-based piezoelectric material powder was dispersed in a sodium silicate solution as the viscous liquid material E of the sintering raw material. is there.

That is, in the same manner as in Example 4, a PZT powder having an average particle size of 2.2 μm was obtained, and the PZT powder was dispersed and mixed in a 10 wt% sodium silicate solution to obtain a sintered raw material paste (viscous liquid E ) Was prepared. Here, as sodium silicate, sodium metasilicate Na ₂ SiO ₃ having a molar ratio n of SiO _{2 to} Na ₂ O of 1 is used, and a 10 wt% sodium silicate solution is 30 wt% with respect to 100 parts by weight of PZT powder. It mixed so that it might become a part. Therefore, the proportion of sodium silicate in the paste is about 3 parts by weight with respect to 100 parts by weight of the PZT powder. Moreover, the viscosity of the obtained paste was 2000 mPa · s.
Further, as the first mask member, a rectangular thin plate (200 openings) made of SUS304 having the same opening as in Example 1 is prepared, and as a metal thin plate to be the first electrode, a 50 μm thick SUS316 made of SUS316 is prepared. Prepare a paste and apply the paste (viscous liquid D) onto the first mask member using a squeegee, and fill each opening of the first mask with the same paste as in Example 1. Then, after drying with warm air (air at 40 ° C. was blown), the first mask member was removed, and the divided sintered raw material layers were dispersedly formed at a total of 200 locations.
Then, it put into the electric furnace, heated to 500 degreeC with the temperature increase rate of 500 degreeC / hr in the air atmosphere, and hold | maintained at 500 degreeC for 1 hour, it fired, and the furnace age was carried out. Thereby, what obtained by baking the sintered sintered body layer with a thickness of 60 μm mainly composed of fired PZT was obtained at a total of 200 locations on the metal thin plate to be the first electrode.

  Furthermore, using the same 2nd mask member as Example 1, the 2nd electrode was formed on each division | segmentation sintered compact layer by application | coating and baking (however, baking temperature is 300 degreeC) of silver paste, and obtained. The laminated body was subjected to collective polarization treatment in the same manner as in Example 1, and then separated and cut into 200 pieces, and then lead wires were attached to obtain 200 ultrasonic thickness sensors.

  As for each ultrasonic thickness sensor after the polarization treatment, the polarization state was examined using a d33 meter. As a result, it was confirmed that the polarization was satisfactorily polarized, and the ultrasonic thickness sensor was actually made of stainless steel with an outer diameter of 10 cm. When the thickness of the tube wall was measured by adhering it to the tube wall of a tube having a thickness of 8 mm using a gold paste as an adhesive, it was confirmed that the tube worked well and the thickness was measured correctly.

In Example 6, as the viscous liquid material A of the sintering raw material, a slurry of a mixture of PZT powder as an oxide-based piezoelectric material powder and an alkoxide sol of a metal component of PZT is used as in Example 1. This is an example when 200 ultrasonic thickness sensors are manufactured at the same time.
In this Example 6, as the slurry (viscous liquid) as the sintering raw material, the same one as in Example 1 is used, and the metal to be the first electrode of many ultrasonic thickness sensors to be finally obtained A thin plate made of SUS304 as in Example 1 was also used.
On the other hand, as the first mask member, a 50 cm thick 30 cm × 30 cm square thin plate made of SUS304 was used, and the size and arrangement of the openings were different from those in Example 1. That is, openings (10 mm circles) corresponding to 10 sintered body layers of the ultrasonic thickness sensor to be finally obtained were arranged in a total of 20 rows at intervals of 5 mm.

And using such a 1st mask member, like Example 1, application | coating of a slurry, drying, the removal of a 1st mask member, and the polarization process were performed. In the subsequent separation step, the metal thin plate is divided for each sectioned sintered body layer so that one sectioned sintered body layer corresponding to 10 ultrasonic sensors is divided into 10 pieces, for a total of 200 pieces. An ultrasonic thickness sensor was obtained.
In this case as well, it was confirmed that there was no problem in the polarization characteristics as in the case of Example 1, and that it could be applied to the thickness measurement at the curved portion without any trouble.

  The preferred embodiments and examples of the present invention have been described above. However, these embodiments and examples are merely examples within the scope of the present invention, and do not depart from the spirit of the present invention. Thus, addition, omission, replacement, and other changes of the configuration are possible. That is, the present invention is not limited by the above description, is limited only by the scope of the appended claims, and can be appropriately changed within the scope.

DESCRIPTION OF SYMBOLS 1 Metal thin plate 3 1st mask member 5 1st opening part 7 Section sintered raw material layer 9 Section sintered body layer 11 2nd mask member 13 2nd opening part 15 2nd electrode 17A, 17B For polarization processing Electrode 21 Ultrasonic thickness sensor 31 First electrode 33 Sintered body layer 41 Thickness measurement object

Claims (18)

A plurality of divided sintering raw material layers each made of a sintering raw material each containing an oxide-based piezoelectric material are divided at intervals on one plate surface of a thin metal plate to be the first electrode in a number of ultrasonic thickness sensors. A step of forming a divided sintered raw material layer to be formed;
The sintered raw materials are fired by heating each of the divided sintered raw material layers at once, whereby a plurality of divided sintered materials each comprising a sintered body of an oxide-based piezoelectric material having a density in the range of 70 to 80%. A firing step of forming a bonded layer on the plate surface at an interval;
A second electrode forming step of forming a second electrode on the surface of each sectioned sintered body layer,
A polarization treatment step of applying a potential difference between the other plate surface of the metal thin plate and the surfaces of a plurality of second electrodes to polarize the plurality of segmented sintered body layers;
After the polarization treatment, a separation step in which the metal thin plate is cut in the thickness direction between at least adjacent divided sintered body layers, and a plurality of ultrasonic sensors each having a sintered body layer are separately formed.
The manufacturing method of the ultrasonic thickness sensor characterized by having.   A viscous liquid material containing an oxide-based piezoelectric material is used as the sintering raw material, and the viscous liquid material is layered at an interval on one plate surface of the metal thin plate in the step of forming the divided sintering raw material layer. The method of manufacturing an ultrasonic thickness sensor according to claim 1, wherein each of the divided sintered raw material layers is formed by adhering.   A first mask member in which a large number of first openings penetrating in the thickness direction are formed at an interval is prepared in advance, and in the step of forming a sectioned sintered material layer, the first mask member is The viscous liquid material is filled in each opening of the first mask member by applying or spraying the viscous liquid material on one surface of the metal thin plate and applying or spraying the viscous liquid material to the surface side of the first mask member. 3. The method of manufacturing an ultrasonic thickness sensor according to claim 2, wherein a plurality of divided sintering raw material layers made of a viscous liquid material are formed on the one plate surface of the metal thin plate at an interval.   4. The method according to claim 3, wherein the first mask member is removed from the one plate surface of the metal thin plate in a stage after the sintering raw material layer section forming step is completed and before the second electrode forming step is started. The manufacturing method of the ultrasonic thickness sensor of description.   A second mask member is prepared in advance, which penetrates in the thickness direction and is formed with a plurality of second openings corresponding to at least a part of the surface of each of the respective divided sintered body layers. In the two-electrode forming step, the second mask member is overlaid on the surface side of the multiple sectioned sintered body layers, and in this state, the conductive paste is applied to the surface side of the second mask member, The ultrasonic wave according to any one of claims 1 to 4, wherein a second electrode is formed on the surface of each sectioned sintered body layer by filling and baking in the opening. Manufacturing method of thickness sensor.   In the polarization treatment step, the other plate surface of the metal thin plate and the surfaces of a large number of second electrodes are sandwiched between a pair of polarization treatment electrodes, and the metal thin plate and each second electrode are collectively The method of manufacturing an ultrasonic thickness sensor according to claim 1, wherein a potential difference is applied and the plurality of sectioned sintered body layers are collectively polarized. .   A mixture of an oxide piezoelectric material powder having an average particle size in the range of 1 to 10 μm and an alkoxide sol of a metal component of the oxide piezoelectric material as the viscous liquid material containing the oxide piezoelectric material. The method of manufacturing an ultrasonic thickness sensor according to claim 2, wherein the ultrasonic thickness sensor is used.   As the viscous liquid material containing the oxide-based piezoelectric material, an oxide-based piezoelectric material powder having an average particle size of 1 to 10 μm and an average particle size of 0.1 to 1.0 μm by decomposition of the metal component alkoxide of the oxide piezoelectric material. A method for producing an ultrasonic thickness sensor according to claim 2, wherein a slurry or paste in which a fine powder of the above is dispersed in a dispersion medium is used.   As the viscous liquid material containing the oxide piezoelectric material, a slurry or paste in which an ultrafine powder having an average particle diameter of 0.15 to 0.25 μm made of an oxide piezoelectric material is dispersed in a dispersion medium is used. The manufacturing method of the ultrasonic thickness sensor of Claim 2.   The heating temperature in the firing step is set in a range of 600 to 800 ° C, and a sectioned sintered body layer having a density in a range of 70 to 80% is obtained. The manufacturing method of the ultrasonic thickness sensor of Claim.   The ultrasonic thickness according to claim 2, wherein a slurry or paste in which an oxide piezoelectric material powder and a low-melting glass powder are dispersed in a dispersion medium is used as the viscous liquid material containing the oxide piezoelectric material. Sensor manufacturing method.   The method of manufacturing an ultrasonic thickness sensor according to claim 11, wherein the low melting point glass powder is a bismuth-based glass powder.   3. The method of manufacturing an ultrasonic thickness sensor according to claim 2, wherein a paste in which an oxide piezoelectric material powder is dispersed in a sodium silicate solution is used as the viscous liquid material containing the oxide piezoelectric material.   The heating temperature in the firing step is set within a range of 450 to 550 ° C, and a sectioned sintered body layer having a density within a range of 70 to 80% is obtained. The manufacturing method of the ultrasonic thickness sensor of Claim.   The metal thin plate having a thickness in the range of 10 to 150 μm is used, the sectioned sintered body layer is formed so that the thickness is in the range of 30 to 150 μm, and the second electrode The method of manufacturing an ultrasonic thickness sensor according to any one of claims 1 to 14, wherein the thickness is formed in a range of 10 to 100 µm.   The method for manufacturing an ultrasonic thickness sensor according to any one of claims 1 to 15, wherein an oxide piezoelectric material having a perovskite crystal structure is used as the oxide piezoelectric material.   17. The method of manufacturing an ultrasonic thickness sensor according to claim 16, wherein a lead zirconate titanate piezoelectric material is used as the oxide piezoelectric material.   The method of manufacturing an ultrasonic thickness sensor according to any one of claims 1 to 17, wherein a thin plate of stainless steel is used as the first electrode.

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