JP3236641B2 - Manufacturing method of composite ferroelectric ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to is a method of manufacturing a composite ferroelectric ceramics <br/> click scan, especially manufactured at low temperatures,
The method of producing a composite ferroelectric ceramics which can be fired molded relates. The present invention is also applicable to piezoelectric filters such as ceramic filters, ceramic oscillators and actuators, pyroelectric elements such as infrared sensors and linear array sensors, and ferroelectric memory elements such as nonvolatile RAM (random access memory). a process for producing a composite ferroelectric ceramics that can be used.

[0002]

2. Description of the Related Art As ferroelectric ceramics or piezoelectric ceramics, Pb (Ti, Zr) O ₃ binary system, Pb (Mg _1/3 Nb _2/3 ) _x Ti _y Zr _z O ₃ has been conventionally used.
Ternary system, Pb (Zn _1/3 Nb _2/3 ) _A (Sn _1/3 Nb
_2/3) is _B Ti _C Zr _D O ₃ ceramic material made of four-component composition and the like. These conventional ceramic materials are almost entirely composed of ceramics, and are produced by molding a raw material or calcined powder into a predetermined shape and then firing at a high temperature. Further, as a ferroelectric which can be manufactured at a relatively low temperature, there is a mixture of the above-mentioned ceramic powder and an organic substance such as rubber or epoxy resin.

[0003]

SUMMARY OF THE INVENTION Conventional ferroelectric ceramics and piezoelectric ceramics generally have high firing temperatures,
It is necessary to fire at a high temperature of 1100 to 1300 ° C. For this reason, the internal electrodes and the like constituting the element are exposed to the high firing temperature as described above, and therefore, it is necessary to use expensive platinum or the like which is hardly oxidized or deteriorated even at a high temperature. Become. Therefore, there is a problem that the cost is high as an element such as various parts, and it is difficult to use it for general purposes.

Further, when the ferroelectric ceramics can be made thinner, for example, a piezoelectric element or a ferroelectric memory can be made thinner, so that it can be operated at a low voltage and the size can be reduced. The element has a great advantage, such as a reduction in heat capacity and an improvement in sensitivity when thinned.However, conventional materials are difficult to make thinner and the substrate material is expensive, and the heat resistance is excellent. There is a problem that it is limited to ceramics and the like.

On the other hand, ferroelectrics composed of a mixture with an organic substance have disadvantages such as poor heat resistance and low mechanical quality factor (mechanical Q), making it impossible to form an oscillator or a ceramic filter.

The present invention, wherein in order to solve the conventional problems, and an object thereof is to provide a ferroelectric ceramics manufacturing method having excellent heat resistance with firing at a low temperature, can be manufactured.

[0007]

To achieve the above object, a method for producing a composite ferroelectric ceramic according to the present invention comprises :
A method for producing a composite ferroelectric ceramic comprising at least a composite of a ferroelectric ceramic powder and a glass , wherein at least the ferroelectric ceramic powder and the glass
And mixed powder having an average particle size of 0.6 μm or less
After crushing, it is molded and fired .

In the above structure, the glass is crystallized.
Preferably, it is a fossilized glass .

Further, in the above configuration, at least
Flatten the dielectric ceramic powder and glass with a medium stirring mill.
After mixing and grinding to an average particle size of 0.6 μm or less, before molding
In addition, it is preferable to further include a whisker .

Further, said in the manufacturing method of composite ferroelectric ceramics of the present invention, the average length of the whiskers
It is preferably 50 μm or less .

As the ferroelectric ceramic powder used in the present invention, any ferroelectric ceramic powder may be used. Specifically, for example, a binary Pb (Ti, Zr) O ₃ system, Pb (Mg _{1 / 3} Nb _2/3 ) _x Ti _y Zr _z O ₃ ternary system (however, X + Y + Z = 1), Pb (Zn _1/3 Nb)
_{2/3) A (Sn 1/3 Nb 2/3} ) B Ti C Zr D O 3 quaternary system (where, A + B + C + D = 1) ceramic material made of such composition, BaTiO _3, PbTiO _3, PbNb
₂ O ₆ , (Na, K) NbO _{3 and the} like, and those having an average particle diameter of 2 μm or less are preferably used. Of course, those having a large average particle diameter may be pulverized by a ball mill or the like, for example. The lower limit of the particle size of the ferroelectric ceramic powder may be any particle size that exhibits ferroelectricity. Further, other various ceramic materials, for example, various ceramics such as alumina, zirconia, titania, and the like may be appropriately used within a range not to impair the object of the present invention. However, if these are used in an excessively large amount, the ferroelectricity is lowered and the sinterability is lowered.

The glass used in the present invention is not particularly limited, and various types of glass can be used. Preferred examples thereof include PbO.B ₂ O ₃ glass, PbO ₂
O.B ₂ O ₃ .SiO ₂ glass, PbO.ZnO.B
Various glasses such as ₂ O ₃ -based glass and ZnO · B ₂ O ₃ · SiO ₂ -based glass can be used. In particular, it is preferable to use crystallized glass obtained by crystallizing these, from the viewpoint of improving the heat resistance of the composite ferroelectric ceramic of the present invention. Further, it is desirable that the glass is chemically stable and has a coefficient of thermal expansion close to that of ferroelectric ceramics.

The mixing ratio between the ferroelectric ceramic powder and the glass is usually 10 to 90%.
Glass is preferably used in a range of 90 to 10 vol% with respect to vol%.

In the case where the ferroelectric ceramic powder and glass are mixed and pulverized, it is preferable to use a medium stirring mill because the pulverization can be performed in a very short time. When whiskers are used in combination, for example, magnesia whiskers, zirconia whiskers, SiC whiskers, ZnO whiskers, potassium titanate whiskers,
There is no particular limitation as long as the object of the present invention can be achieved, such as Si ₃ N ₄ whiskers and zirconia whiskers, and other appropriate whiskers can be used. Even if the whisker itself is slightly conductive, it can be used without any problem as long as it has high resistance as a composite ferroelectric ceramic.

The whiskers in the present invention include fibrous glass such as fiber, for example, quartz glass fiber having good heat resistance, and ceramics, for example, barium titanate, strontium titanate.
If the length of the whiskers exceeds 50 μm, the density of the composite ferroelectric decreases, and the ferroelectricity decreases, which is undesirable. It is preferable to use a whisker having a length of 50 μm or less. When the average particle diameter of the ferroelectric ceramic powder is small, the length of the whisker is preferably reduced accordingly. Usually, the length of the whisker is preferably 2 μm or more in order to exhibit the effect of improving the bending strength.

It is preferable to use whiskers in a range of usually 15 vol% or less, since a sharp decrease in ferroelectricity does not occur. For molding, various molding methods that can be used for molding ceramic powders can be adopted, for example, pressure molding, casting molding,
Appropriate materials such as extrusion molding, doctor blade method, dipping method, and printing method can be applied.

The firing temperature may be around the sintering temperature of the glass,
Therefore, firing at a low temperature becomes possible. Since the specific firing temperature varies depending on the type of material used, it cannot be specified unconditionally. For example, the firing temperature is usually in the range of about 300 ° C. to 800 ° C. However, it is not limited to this.

FIG. 1 is a conceptual diagram showing an example of a cross-sectional structure of a composite ferroelectric ceramic 1 comprising a ferroelectric ceramic powder 2 and a glass 3 obtained by the method of the present invention. The dielectric ceramic powder 2 has a configuration in which the dielectric ceramic powder 2 is randomly dispersed and dispersed in the matrix of the glass 3, and three-dimensionally, the glass region itself forms a three-dimensional continuous layer.

The piezoelectric element obtained by applying an electrode to the composite ferroelectric ceramic obtained by the method of the present invention can be used as an oscillator, a ceramic filter, a piezoelectric actuator, and an electrode is provided to the composite ferroelectric ceramic of the present invention. By doing so, it can be used as a pyroelectric element or a ferroelectric memory.

FIG. 2 is a schematic sectional view showing an example of the structure of a piezoelectric element, a pyroelectric element or a ferroelectric memory element 4 made of the composite ferroelectric ceramics 1 obtained by the method of the present invention. Electrodes 5 are formed on both surfaces of the composite ferroelectric ceramic 1.

Further, the ferroelectricity of the composite ferroelectric ceramic obtained by the method of the present invention can be controlled in a wider range than before by changing the mixing ratio with glass.

[0022]

The method for producing a composite ferroelectric ceramic of the present invention.
At least ferroelectric ceramic powder and glass
After mixing and grinding to an average particle diameter of 0.6 μm or less, molding,
Since firing, high-density ferroelectric ceramics at low temperature
Can be manufactured.

The composite ferroelectric ceramic of the present invention
In the manufacturing method of
More heat-resistant composite that can be manufactured at lower temperatures
Ferroelectric ceramics can be provided.

The composite ferroelectric ceramic of the present invention
In the production method of the above , by further adding a whisker , it is possible to provide a composite ferroelectric ceramic having high mechanical strength, which can be produced at a low temperature.

[0025] In addition, the length of the average of the Daewoo Isuka 5
By setting the thickness to 0 μm or less, it is possible to provide a high-density composite ferroelectric ceramic having high mechanical strength and which can be manufactured at a low temperature.

[0026]

EXAMPLES Hereinafter, the present invention will be described with reference to examples to facilitate understanding of the present invention, but the present invention is not limited to only these examples.

Example 1 Pb (Zn _1/3 Nb) was used as a ferroelectric ceramic powder.
_2/3 ) _0.09 (Sn _1/3 Nb _2/3 ) _0.09 Ti _0.42 Zr _0.40
A calcined powder having a composition ratio of O ₃ +0.5 wt.% MnO ₂ (a powder obtained by mixing the raw materials, calcining at 1250 ° C. for 2 hours, and then pulverizing with a ball mill to an average particle diameter of about 4 μm) and a glass powder (Nippon Electric Glass) Ltd. PbO · B ₂ O ₃ based glass powder, No. CF-8, average particle size 3.8 .mu.m, Note, and weighed in the proportions shown this to the glass contains some ceramic powder) to (Table 1) After that, using ethanol as a dispersion medium, a medium stirring mill (“Motor Mill M50” manufactured by Eiger Engineering Co., Ltd., pulverizing medium: zirconia cobblestone having a diameter of 0.4 mm, peripheral speed of a stirrer of 10 m / s), an average particle diameter of about 0.2 μm
m, and then dried.

Then, after granulation using pure water, 50
The mixture was passed through a 0 μm sieve and sized. This powder was formed into a disc-shaped compact having a diameter of 13 mm and a thickness of about 1 mm by pressure molding using a mold, and was fired in an electric furnace for 2 hours to produce a composite ferroelectric ceramic. . Temperature rise / fall rate is 400 ℃
/ H.

After firing, a Cr-Au vapor deposition electrode was provided on both surfaces. Then, a DC electric field of 3 kV / mm was applied between the electrodes for 30 minutes in silicon oil at 100 ° C. for 30 minutes to perform polarization treatment, thereby producing a piezoelectric element as shown in FIG. This sample was measured for dielectric constant, coupling coefficient, and the like. The measurement results are shown in (Table 1).

[0030]

[Table 1]

As is clear from Table 1, the composite ferroelectric ceramics of the present invention was the same as that of Comparative Example. Although the coupling coefficient and the dielectric constant are slightly lower than those of the ferroelectric ceramic of No. 8, they can be manufactured at a remarkably low temperature. Note that N
o. In Comparative Examples not containing 8 glass, if when the sintering temperature was 1000 ° C. or less, with none sinter, the coupling coefficient (electromechanical coupling factor (kp)) is 0, not exhibit piezoelectricity Absent.

In addition, No. The average particle size of the mixed and pulverized product after mixing and pulverization with a medium stirring mill at the same compounding ratio as in Example 1 was 1.
9, 0.92, 0.58, 0.22, and 0.052 μm
Then, the density of the sintered body is 9
2, 94, 98, 98 and 98%, and when the average particle diameter after mixing and pulverization is 0.6 μm or less, firing can be performed at high density.
If it is 0.6 μm or more, it is difficult to obtain a dense ceramic having a low firing density.

In the above embodiment, the ferroelectric ceramic powder and glass were mixed and pulverized with a medium stirring mill.
After both are pulverized separately, they may be mixed. In this case, the average particle size of the ferroelectric ceramic powder is 2 μm.
m or less. If it exceeds 2 μm, the sinterability is significantly reduced. That is, when the average particle diameter of the ferroelectric ceramic powder is 4.2, 1.8, and 0.45 μm, the density of the sintered body is 69, 88, and 94% of the theoretical density, respectively. When the average particle size of the dielectric ceramic powder exceeds 2 μm, the sintered density is low. Mixing and grinding with a medium stirring mill is preferable because the degree of mixing of the ferroelectric ceramic powder and the glass is improved, and the homogeneity of the composite ferroelectric ceramic is improved and the sinterability is also improved.

Example 2 Pb (Zn _1/3 Nb) was used as a ferroelectric ceramic powder.
_2/3 ) _0.09 (Sn _1/3 Nb _2/3 ) _0.09 Ti _0.42 Zr _0.40
A calcined powder having a composition ratio of O ₃ +0.5 wt.% MnO ₂ (a powder obtained by mixing the raw materials, calcining at 1250 ° C. for 2 hours, and then pulverizing with a ball mill to an average particle diameter of about 4 μm) and a glass powder (Nippon Electric Glass) Ltd. PbO · B ₂ O ₃ based glass powder, No. CF-8, average particle size 3.8 .mu.m, Note, and weighed in the proportions shown this to the glass contains some ceramic powder) to (Table 2) After that, using ethanol as a dispersion medium, a medium stirring mill (“Motor Mill M50” manufactured by Eiger Engineering Co., Ltd., pulverizing medium: zirconia cobblestone having a diameter of 0.4 mm, peripheral speed of a stirrer of 10 m / s), an average particle diameter of about 0.2 μm
m, and then dried.

The mixed and ground powder and magnesia whisker (magnesia having an average diameter of about 2 μm and an average length of 24 μm)
Was mixed in the ratio shown in Table 2 and granulated using pure water, and passed through a 500 μm sieve to regulate the size. This powder was formed into a disc-shaped compact having a diameter of 13 mm and a thickness of about 1 mm by pressure molding using a mold, and was baked in an electric furnace for 2 hours to produce a composite ferroelectric ceramic. . The rate of temperature rise / fall is 400 ° C./h. After baking, a vapor deposition electrode of Cr-Au was provided on both surfaces. Thereafter, a DC electric field of 3 kV / mm was applied between the two electrodes in silicon oil at 100 ° C. for 30 minutes to perform a polarization treatment to produce a piezoelectric element. This sample was measured for dielectric constant, coupling coefficient, bending strength and the like. The measurement results are shown in (Table 2).

[0036]

[Table 2]

As shown in Table 2, the composite ferroelectric ceramics containing whiskers can have higher bending strength than those not containing whiskers. In addition,
As described above, any suitable whisker other than the examples can be used as the whisker as long as the object of the present invention can be achieved, such as zirconia and SiC whisker.

Embodiment 3 Nos. 1 and 2 of Embodiments 1 and 2. Regarding 3 and 10, as the material of the glass, crystallized glass (PbO.
ZnO / B ₂ O ₃ powder glass: Part number LS-7105,
A composite ferroelectric ceramic was produced in substantially the same manner as in the above example except that the average particle diameter was 7.5 μm. The deformation temperature was a temperature at which the corners of the disc-shaped sample were rounded when each temperature was maintained for 5 hours. For these samples, the coupling coefficient, dielectric constant, dielectric loss tangent, deformation temperature, and the like were measured. The measurement results are shown in (Table 3).

[0039]

[Table 3]

As shown in Table 3, when crystallized glass is used as the glass, the deformation temperature is significantly higher than when non-crystallized glass is used, and the heat resistance of the composite ferroelectric ceramic is significantly improved. did. Therefore, composite ferroelectric ceramics using crystallized glass are preferable because they can withstand high-temperature processing and heat treatment.

The composite ferroelectric ceramic obtained in the present invention was provided with an electrode and then subjected to a polarization treatment.
The piezoelectric element made of the composite ferroelectric ceramic of No. 5 was applied with a DC electric field of 2 kV / mm between both electrodes of the disc-shaped element, and the displacement was measured using a differential transformer type displacement meter. It was 0.38 μm in the direction, and the operation was confirmed as an actuator.

The composite ferroelectric ceramics obtained in the present invention was provided with Cr-Au vapor deposition electrodes on both surfaces and then subjected to polarization treatment. By applying a temperature change to the element made of the composite ferroelectric ceramic of No. 5, a voltage was generated between both electrodes of the disc-shaped element, and the operation as a pyroelectric element was confirmed.

The composite ferroelectric ceramic obtained according to the present invention was provided with an electrode in Example 1, As a result of measuring the electric flux density-electric field hysteresis curve (DE hysteresis curve) of the composite ferroelectric ceramic element No. 5, the coercive electric field Ec was 2.3 kV / mm, and the remanent polarization Pr was 14.6.
μC / cm ² and operated as a ferroelectric memory element.

As described above, in the embodiments of the present invention, the characteristics of the bulk element are shown. However, the present invention is not limited to the bulk, and may be a thin film element. By reducing the particle diameter of the ferroelectric ceramic powder or the glass powder, the thickness of the composite ferroelectric ceramic can be reduced as much as possible. Further, the composite ferroelectric ceramic of the present invention may be formed on a substrate or an electrode of various ceramics or a metal such as stainless steel. In addition, the composite ferroelectric ceramics obtained in the present invention,
The process may include a small amount of pores.

As described above, the composite ferroelectric ceramic of the present invention
The method of manufacturing is significantly can be produced at a lower temperature than the conventional ferroelectric ceramics. For this reason, a large-area thin-film ferroelectric ceramic can be formed on various substrates such as a metal plate such as stainless steel by a coating method or the like. In the present invention, the composite ferroelectric ceramics and the piezoelectric element, the pyroelectric element, and the ferroelectric memory which are easily formed into a thin film by making the ferroelectric ceramic powder and the glass powder finer can be used. The thickness of the element can be reduced to the order of nanometers.

[0046]

The production of the composite ferroelectric ceramic of the present invention.
Manufacturing method produces high density ferroelectric ceramics at low temperature
Can provide a way to Therefore, the composite obtained by the method of the present invention
Synthetic ferroelectric ceramics can be effectively used for the production of various elements even in combination with a material having low heat resistance, which could not be used until now.

The composite ferroelectric ceramic of the present invention
In the manufacturing method of
More heat-resistant composite that can be manufactured at lower temperatures
A method for producing a ferroelectric ceramic can be provided.

Further, the composite ferroelectric ceramic of the present invention
In the production method of the above , by further adding a whisker , it is possible to provide a production method of a composite ferroelectric ceramic which can be produced at a low temperature with higher mechanical strength.

[0049] In addition, the length of the average of the Daewoo Isuka 5
When the thickness is 0 μm or less, it is possible to provide a method for producing a high-density composite ferroelectric ceramic having high mechanical strength and capable of being produced at a low temperature.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a cross-sectional structure of a composite ferroelectric ceramic obtained by a method of the present invention.

FIG. 2 is a schematic sectional view showing an example of the structure of a piezoelectric element, a pyroelectric element or a ferroelectric memory element made of a composite ferroelectric ceramic obtained by the method of the present invention.

[Explanation of symbols]

 1. 1. Composite ferroelectric ceramics 2. Ferroelectric ceramic powder Glass 4. 4. Piezoelectric element, pyroelectric element or ferroelectric memory element electrode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-100052 (JP, A) JP-A-54-118564 (JP, A) JP-A-58-194758 (JP, A) 184207 (JP, A) JP 54-4077 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01B 3/00-3/02 C03C 8/24 C03C 14/00 H01L 41/24

Claims (4)

(57) [Claims] 1. A method for producing a composite ferroelectric ceramic comprising at least a composite of a ferroelectric ceramic powder and a glass, wherein at least the ferroelectric ceramic powder and the glass are mixed in a medium stirring mill with an average particle size of 0%. 0.6μ
m, followed by mixing and grinding, followed by molding and firing. 2. The method according to claim 1, wherein the glass is crystallized glass.
A method for producing the composite ferroelectric ceramic according to the above. 3. At least a ferroelectric ceramic powder and
Reduce the average particle diameter to 0.6μm or less with a medium stirring mill with glass
After mixing and pulverizing, add whiskers before molding.
The composite ferroelectric according to claim 1 or 2, wherein
Method for producing conductive ceramics. 4. The whisker has an average length of 50 μm or less.
The composite ferroelectric ceramics according to claim 3,
Construction method.