JP3936870B2 - Piezoelectric vibrator and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric vibrator used for a resonator and the like and a manufacturing method thereof.
[0002]
[Prior art]
A piezoelectric body is a material having a piezoelectric effect in which electric polarization changes by receiving an external stress and an inverse piezoelectric effect in which distortion is generated by applying an electric field. Piezoelectric materials are applied to sensors, resonators, actuators, and the like.
[0003]
Most of piezoelectric materials currently in practical use are tetragonal or rhombohedral PZT (PbZrO_Three-PbTiO_ThreeSolid solution) and tetragonal PT (PbTiO)_ThreeFerroelectric materials having a perovskite structure such as) are generally used. And by adding various subcomponents to these, it is possible to cope with various required characteristics.
[0004]
However, many PZT and PT piezoelectric materials have a Curie point of about 200 to 400 ° C. in practical compositions, and become paraelectric at higher temperatures and lose their piezoelectric properties. It is difficult to apply to the intended use. In addition, these lead-based piezoelectric materials contain a large amount (about 60 to 70% by mass) of lead oxide (PbO) that is extremely volatile even at low temperatures, which is preferable from the viewpoint of ecology and pollution prevention. Absent. Specifically, when manufacturing these lead-based piezoelectric materials as ceramics or single crystals, heat treatment such as firing and melting is unavoidable, and when considered at the industrial level, lead oxide, which is a volatile component, in the atmosphere The amount of volatilization and diffusion is extremely large. Lead oxide released in the manufacturing stage can be recovered, but most of lead oxide contained in piezoelectric materials put on the market as industrial products is currently unrecoverable, and these are widely used in the environment. It is inevitable that it will cause pollution if released to the public.
[0005]
Examples of piezoelectric materials that do not contain lead at all include, for example, BaTiO having a perovskite structure belonging to the tetragonal system._ThreeIs well known, but this is not practical because the Curie point is as low as 120 ° C.
[0006]
As a piezoelectric material having a relatively high Curie point, for example, a bismuth layered compound is known. Many of the bismuth layered compounds have a high Curie point, so that sufficient characteristics can be obtained as a high-temperature sensor. However, a bismuth layered compound containing no lead is important when applied to a resonator._maxThere is a problem that is small. Q_maxIs the maximum phase angle θ_maxTanθ_maxIt is. That is, it is the maximum value of Q (= | X | / R) between the resonance frequency and the antiresonance frequency, where X is reactance and R is resistance. Q_maxIs larger, that is, θ_maxIs closer to 90 °, the oscillation becomes more stable, and oscillation at a low voltage becomes possible.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a piezoelectric vibrator having a piezoelectric substrate having a sufficiently high Curie point and exhibiting excellent piezoelectric characteristics.
[0008]
[Means for Solving the Problems]
The above object is achieved by the present inventions (1) to (8) below.
(1) A piezoelectric vibrator having a piezoelectric substrate containing a bismuth layered compound and vibration electrodes formed on both surfaces of the piezoelectric substrate,
A piezoelectric vibrator in which a work-affected layer is not substantially present on a vibration electrode forming surface of the piezoelectric substrate.
(2) A piezoelectric vibrator having a piezoelectric substrate containing a bismuth layered compound, and vibration electrodes formed on both sides of the piezoelectric substrate,
A piezoelectric vibrator in which an a-axis orientation degree of the bismuth layered compound is less than 12.8% on the vibration electrode forming surface of the piezoelectric substrate.
(3) The piezoelectric vibrator according to (2), wherein a center line average roughness Ra of the piezoelectric substrate is less than 0.27 μm.
(4) The bismuth layered compound is M^II(M^IIContains an element selected from Sr, Ba and Ca), Bi, Ti, O and a lanthanoid oxide, M^IIBi_FourTi_FourO₁₅When the lanthanoid is represented by Ln, the atomic ratio Ln / (Ln + M^II)But
0 <Ln / (Ln + M^II<0.5
The piezoelectric vibrator according to any one of (1) to (3) above.
(5) A method of manufacturing a piezoelectric vibrator having a piezoelectric substrate containing a bismuth layered compound and vibration electrodes respectively formed on both surfaces of the piezoelectric substrate,
After polishing the sintered body containing the bismuth layered compound to obtain a sintered body thin plate, the temporary electrode is formed on the polished surface in the primary polishing process and subjected to polarization treatment, and then the temporary electrode is removed. Secondary polishing using abrasive grains having a grain size smaller than that of the abrasive grains used in the secondary polishing process and the secondary polishing process for polishing the surface on which the temporary electrode of the sintered thin plate was formed A method for manufacturing a piezoelectric vibrator, comprising: a final polishing step for polishing a polished surface in the step; and a step of forming a vibrating electrode on the polished surface in the final polishing step.
(6) A method of manufacturing a piezoelectric vibrator having a piezoelectric substrate containing a bismuth layered compound and vibration electrodes respectively formed on both surfaces of the piezoelectric substrate,
After polishing the sintered body containing the bismuth layered compound to obtain a sintered body thin plate, the temporary electrode is formed on the polished surface in the primary polishing process and subjected to polarization treatment, and then the temporary electrode is removed. A polishing process for polishing, a polishing process for polishing a surface of the sintered thin plate on which the temporary electrode has been formed, using an abrasive grain having a grain size smaller than that used in the primary polishing process, and a finishing polishing process Forming a vibrating electrode on the polished surface of the piezoelectric vibrator.
(7) The method for manufacturing a piezoelectric vibrator according to (5) or (6), wherein abrasive grains having an average particle size of less than 6.7 μm are used in the finish polishing step.
(8) The piezoelectric vibration according to any one of (5) to (7), wherein in the finish polishing step, polishing is performed so that the degree of orientation of the a-axis of the bismuth layered compound on the surface of the sintered thin plate is less than 12.8%. Child manufacturing method.
[0009]
[Action and effect]
FIG. 1C shows a process path diagram when manufacturing a conventional piezoelectric vibrator. First, in the sintered body manufacturing process, a sintered body of a bismuth layered compound is manufactured. Next, in the primary polishing step, the sintered compact is obtained by polishing the sintered compact until the surface becomes smooth and has a thickness suitable for polarization treatment. Next, a temporary electrode is formed on the polished surface of the sintered thin plate and polarized by applying a DC electric field using the temporary electrode, and then the temporary electrode is removed. Next, in the secondary polishing step, the surface on which the temporary electrode has been formed is polished until the thickness becomes appropriate as a vibrator, whereby a piezoelectric substrate is obtained. Next, a vibrating electrode is formed on the polished surface of the piezoelectric substrate to form a piezoelectric vibrator.
[0010]
In such a process flow, relatively coarse abrasive grains are used in the primary polishing process and the secondary polishing process in order to ensure sufficient throughput.
[0011]
From the experiments described below, the inventors of the present invention produced a work-affected layer on the polished surface of the piezoelectric substrate in the secondary polishing step._maxWas found to deteriorate. In this experiment, first, a sintered thin plate, which is a non-oriented polycrystalline body, was polished with abrasive grains having an average particle size of 6.7 μm to obtain a piezoelectric substrate. After this polishing, the crystal orientation of the polished surface was measured by the Lotgering method described later. As a result, it was found that the degree of crystal orientation on the surface of the piezoelectric substrate was increased by polishing. This increase in the degree of crystal orientation is due to the generation of a work-affected layer on the polished surface. This work-affected layer is considered to be a region where minute cracks or crystal orientation occurs. On the other hand, when abrasive grains having an average particle size of 2.0 μm were used for polishing the sintered compact, the degree of crystal orientation on the polished surface was lowered, and accordingly Q_maxImproved more than twice.
[0012]
Based on such experimental results, in the first aspect of the present invention, as shown in FIG. 1A, after the secondary polishing, abrasive grains having a particle size smaller than that used for the secondary polishing are used. A finish polishing step for polishing the secondary polishing surface is provided. As a result, the work-affected layer existing on the secondary polished surface is substantially removed, and as a result, Q_maxIn particular, in the high frequency range of about 20 to 70 MHz in the thickness longitudinal vibration, the Q that is remarkably larger than the conventional one is obtained._maxIs obtained. Further, since the fine abrasive grains are used only in the finish polishing step, the throughput is not greatly reduced.
[0013]
In the second aspect of the present invention, as shown in FIG. 1B, a finish polishing step is provided in place of the conventional secondary polishing step. Conventionally, abrasive grains having the same particle size were used in primary polishing and secondary polishing, but in the final polishing step in the second aspect, abrasive particles having a particle size smaller than that used in primary polishing were used. To polish the primary polishing surface. In this final polishing step, the work-affected layer present on the primary polishing surface is substantially removed. As a result, a large Q is obtained as in the first embodiment._maxIs obtained.
[0014]
The degree of removal of the work-affected layer can be determined by the degree of crystal orientation of the polished surface.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The piezoelectric vibrator manufactured according to the present invention has a piezoelectric substrate containing a bismuth layered compound, and vibration electrodes formed on both sides of the piezoelectric substrate.
[0016]
Bismuth layered compounds have the general formula
(Bi₂O₂)²⁺(A_m-1B_mO_{3m + 1})^2-
It is a perovskite type compound represented by these. In the above general formula, the element A is at least one of 1 to 3 metal elements, and the element B is at least 1 to 2 to 6 metal elements. Examples of the element A include alkali metal elements such as Na and K, alkaline earth metal elements such as Ca, Sr, and Ba, rare earth elements such as Y, La, Gd, and Nd, and heavy metals such as Pb, Cd, and Bi. The metal element selected is preferred. The element B is preferably a transition metal element such as Ti, Zr, V, Nb, Ta, Mo, W, Mg, Zn, Mn, Fe, Co, Ni, and Cr. It is preferable to use at least one of Nb and Ta.
[0017]
As the bismuth layered compound, for example, SrBi₂Nb₂O₉, SrBi₂Ta₂O₉, BaBi₂Nb₂O₉, BaBi₂Ta₂O₉, PbBi₂Nb₂O₉, PbBi₂Ta₂O₉, BaBi_ThreeTi₂NbO₁₂, PbBi_FourTi_FourO₁₅, SrBi_FourTi_FourO₁₅, CaBi_FourTi_FourO₁₅, BaBi_FourTi_FourO₁₅, Na_0.5Bi_4.5Ti_FourO₁₅, K_0.5Bi_4.5Ti_FourO₁₅, Sr₂Bi_FourTi_FiveO₁₈, Ba₂Bi_FourTi_FiveO₁₈, Pb₂Bi_FourTi_FiveO₁₈And a solid solution containing two or more of these, and among these, those containing no Pb are preferred because of their low environmental impact.
[0018]
Of these, the large Q_maxAnd Q according to the present invention._maxThe improvement effect is particularly high.^II(M^IIContains at least one element selected from Sr, Ba and Ca), Bi, Ti, O and a lanthanoid oxide;^IIBi_FourTi_FourO₁₅When the lanthanoid is represented by Ln, the atomic ratio Ln / (Ln + M^II)But
0 <Ln / (Ln + M^II) <0.5, preferably
0.03 ≦ Ln / (Ln + M^II) ≦ 0.3
Is a bismuth layered compound. Lanthanoids are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. Among these, at least one of La, Nd, Sm, Gd, Dy, Ho, Er, and Yb is preferable, and La is most preferable. Ln / (Ln + M^II) Is too large, Q_maxHowever, it becomes lower.
[0019]
M^IIBi_FourTi_FourO₁₅In a bismuth layered compound containing a type crystal, QM can also be obtained by adding a Mn oxide._maxCan be improved. In particular, by adding Mn oxide and Ln oxide in combination, Q_maxCan be significantly improved. However, if the content of Mn oxide is too large, the insulation resistance becomes low and polarization treatment becomes difficult. Therefore, the content of Mn oxide is preferably less than 0.62% by mass, more preferably in terms of MnO. Is 0.60 mass% or less, more preferably 0.43 mass% or less. On the other hand, in order to sufficiently exhibit the effect of the addition of Mn oxide, the Mn oxide is preferably contained in an amount of 0.02% by mass or more, particularly 0.03% by mass or more in terms of MnO. In addition, Q can also be added by adding Co oxide._maxCan be improved. Q_maxIn order to sufficiently exhibit the improvement effect, the content in terms of CoO is preferably set to 0.1% by mass or more. However, when there is too much content of Co oxide, insulation resistance becomes low and polarization becomes difficult. Therefore, the content in terms of CoO is preferably less than 0.7% by mass, and more preferably 0.5% by mass or less. Further, by adding Y oxide in combination with Ln oxide, the temperature characteristics of the resonance frequency are improved, and a sufficiently large Q_maxIs obtained. Y oxide content is Y₂O_ThreePreferably, it is 0.5% by mass or less, more preferably 0.4% by mass or less. If there is too much content of Y oxide, Q_maxWill be lower. On the other hand, in order to fully demonstrate the effect of the addition of Y oxide, Y oxide is Y₂O_ThreeIt is preferable to contain 0.05 mass% or more in terms of.
[0020]
M^IIBi_FourTi_FourO₁₅The overall composition of a bismuth layered compound containing type crystals and Ln oxide is generally (M^II _1-aLn_a) Bi_FourTi_FourO₁₅In addition, when Mn oxide, Co oxide, and Y oxide are contained, MnO, CoO, Y₂O_ThreeHowever, it may be deviated from these. For example, M for Ti^IIThe ratio of + Ln and the ratio of Bi to Ti may deviate by about ± 5% from the stoichiometric composition. For example, by increasing the ratio of Bi to Ti, Q_maxCan be made higher. In addition, the amount of oxygen can also vary depending on the valence of the metal element, oxygen defects, and the like.
[0021]
Next, the manufacturing method of this invention is demonstrated.
[0022]
FIG. 1A and FIG. 1B show the flow of steps when manufacturing a piezoelectric vibrator in the first and second aspects of the present invention, respectively.
[0023]
In the first aspect, a step of producing a sintered body containing a bismuth layered compound, a primary polishing step of polishing the sintered body to obtain a sintered body thin plate, and a temporary electrode on the polished surface in the primary polishing step After performing the polarization treatment, the polarization step for removing the temporary electrode, the secondary polishing step for polishing the surface on which the temporary electrode of the sintered thin plate was formed, and the abrasive used in the secondary polishing step A polishing process in which the polishing surface in the secondary polishing process is polished using abrasive grains having a particle size smaller than the grains, and the piezoelectric substrate is shaped so as to have a predetermined shape and size. Forming a vibrating electrode to obtain a piezoelectric vibrator.
[0024]
On the other hand, in the second aspect, a finish polishing step is provided instead of the secondary polishing step. In the final polishing step in the second aspect, the polishing surface in the primary polishing step is polished using abrasive grains having a particle size smaller than that used in the primary polishing step.
[0025]
Hereinafter, each process will be described in detail.
[0026]
Sintered body manufacturing process
The sintered body containing the bismuth layered compound may be produced in the same manner as before, and the production conditions may be appropriately determined according to the composition. The condition described below is M^IIBi_FourTi_FourO₁₅In the case of manufacturing a piezoelectric substrate having a composition containing as a main component. In this step, first, as a starting material, an oxide or a compound that can be converted into an oxide by firing, such as carbonate, hydroxide, oxalate, nitrate, etc., specifically, SrCO_Three, BaCO_Three, CaCO_Three, La₂O_Three, Bi₂O_ThreeTiO₂, MnCO_Three, Y₂O_ThreeEtc. are prepared, and these are wet mixed by a ball mill or the like. Next, the calcined product is calcined at about 650 to 1000 ° C. for about 1 to 3 hours. After wet pulverization, the calcined powder is dried, a small amount of water (about 4 to 8% by mass) is added to the dried material, and after temporary molding at a pressure of about 5 to 50 MPa, cold at a pressure of about 200 to 400 MPa. Molded by an isotropic press to obtain a molded body. At this time, a binder such as polyvinyl alcohol may be added. Next, the molded body is fired to obtain a sintered body. The firing temperature is preferably selected from the range of 950 to 1250 ° C., and the firing time is preferably about 1 to 5 hours. Firing may be performed in the air, or may be performed in an atmosphere having a lower or higher oxygen partial pressure than in the air, or in a pure oxygen atmosphere.
[0027]
The sintered body thus produced is a sintered body in which crystals are not oriented.
[0028]
Primary polishing process
In the primary polishing step, the sintered body is smoothed until the surface is smooth and has a thickness suitable for polarization treatment and a relatively high rigidity so as to facilitate subsequent handling. By polishing, a sintered thin plate is obtained. The thickness of the sintered body after the primary polishing is usually preferably about 160 to 500 μm. The polishing means in the primary polishing is not particularly limited, and may be appropriately selected so that the polished surface of the sintered body is smoothed to such an extent that does not hinder the formation of the temporary electrode described later. Wrapping may be used.
[0029]
The grain size of the abrasive grains used in the primary polishing process is made larger than the grain size of the abrasive grains used in the final polishing process in order to ensure a sufficient polishing rate. In both the first aspect and the second aspect, in the primary polishing step, abrasive grains having a particle size equivalent to that of the abrasive grains used in the secondary polishing step of the first aspect may be used.
[0030]
In FIG. 2, the schematic block diagram of a double-sided simultaneous lapping apparatus is shown. This apparatus has a lower surface plate 2, an upper surface plate 3, and a carrier 4. At the time of lapping, a carrier 4 for holding a workpiece (sintered body) 5 is disposed on the lower surface plate 2, and an abrasive is supplied between the workpiece 5 and the upper and lower surface plates. The abrasive is obtained by dispersing abrasive grains 6 in water or oil, and when water is used as a dispersion medium, a rust inhibitor is added as necessary. When the workpiece 5 is rotated relative to the surface plate while applying a processing pressure in the direction indicated by the arrow in the figure, the workpiece 5 is polished by the abrasive grains 6. When polished with a lapping device, the flatness of the polished surface of the workpiece is improved, and double-sided simultaneous lapping is particularly suitable for polishing a thin and brittle workpiece such as a piezoelectric substrate used in a resonator.
[0031]
Polarization process
In the polarization step, first, if necessary, the sintered thin plate is cut to a predetermined size, and then a temporary electrode is formed on the polished surface in the primary polishing of the sintered thin plate. The constituent material of the temporary electrode is not particularly limited, but Cu is preferable because it can be easily removed by etching with a ferric chloride solution. Vapor deposition or sputtering is preferably used for forming the temporary electrode. The polarization treatment may be performed in the same manner as in the prior art. Specifically, the conditions may be appropriately determined according to the composition of the sintered body. Usually, the polarization temperature is 150 to 250 ° C., and the polarization time is 1 to 30 minutes. The intensity of the polarization electric field may be 1.1 times or more than the coercive electric field.
[0032]
Secondary polishing process
In the secondary polishing step provided in the first aspect, the surface on which the temporary electrode has been formed is polished to bring the sintered thin plate closer to the thickness required for the piezoelectric substrate of the piezoelectric vibrator. As the polishing means in the secondary polishing step, it is preferable to use the lapping described above. In the secondary polishing step, polishing is performed at a high speed for the purpose of adjusting the thickness of the sintered thin plate, and in the final polishing step, at least a part of the work-affected layer generated in the secondary polishing step is removed. Therefore, relatively large-diameter abrasive grains are used in the secondary polishing process, and relatively small-diameter abrasive grains are used in the final polishing process. The average grain size of the abrasive grains used in the secondary polishing process may be determined in relation to the abrasive grains used in the final polishing process, but in order to obtain a sufficiently high polishing rate, the average grain diameter is 6.7 μm or more. Preferably there is. However, if the grain size of the abrasive grains used in the secondary polishing process is too large, defects such as polishing streaks and cracks are likely to occur in the sintered compact, and these defects are difficult to remove in the final polishing process. The average particle size of the abrasive grains used in the secondary polishing step is preferably 11.5 μm or less.
[0033]
The average grain size of the abrasive grains used in the primary polishing step is preferably 6.7 μm or more from the viewpoint of securing a sufficient polishing rate, and 11.5 μm or less from the viewpoint of preventing generation of defects on the polished surface. It is preferable.
[0034]
Final polishing process
In the final polishing step, at least a part, preferably substantially all, of the work-affected layer generated in the immediately preceding polishing step is removed by polishing the polishing surface in the immediately preceding polishing step. At the same time, the sintered thin plate is thinned to a thickness required for the piezoelectric substrate of the piezoelectric vibrator. The thickness required for the piezoelectric substrate differs depending on the operating frequency of the piezoelectric vibrator, but is about 100 to 400 μm when the third harmonic of the thickness longitudinal vibration is used at a frequency of 20 to 70 MHz.
[0035]
The amount of polishing in the final polishing step is preferably 1 μm or more, particularly 5 μm or more in terms of thickness. If the polishing amount is too small, removal of the work-affected layer generated in the immediately preceding polishing step becomes insufficient. On the other hand, the larger the polishing amount, the longer the time required for polishing. In addition, in the first aspect, the polishing rate is slow because fine abrasive grains are used. In the first aspect, the polishing amount in the final polishing step is 50 μm or less. In particular, the thickness is preferably 30 μm or less.
[0036]
On the surface of the sintered compact after completion of finish polishing, the degree of orientation of the a-axis of the bismuth layered compound is less than 12.8%, preferably 12.0% or less. If this degree of orientation is too large, the Q of the piezoelectric vibrator_maxWill become smaller. On the other hand, this degree of orientation may be 0%, but it is difficult to significantly reduce this degree of orientation, and it takes a long time, so it is necessary to reduce this degree of orientation to less than 11.5%. Absent.
[0037]
Here, the degree of orientation of the a-axis in the bismuth layered compound will be described. The bismuth layered compound is (A_m-1B_mO_{3m + 1})^2-A pseudo-perovskite layer consisting of (Bi₂O₂)²⁺It has a structure in which bismuth oxide layers made of are alternately stacked. In this stacked structure, the stacking direction is the c-axis, and the a-axis is in the in-plane direction of the stacking surface. The degree of orientation in this specification is the degree of crystal orientation according to the Lotgering method, which is represented by the following formula (1).
[0038]
(PP₀) / (1-P₀* 100 (1)
[0039]
In the above formula (I), P and P₀Is
ΣI (HKL) / ΣI (hkl) (2)
It is represented by In the above formula (2), ΣI (hkl) is the total sum of X-ray diffraction intensities derived from all of the crystal planes. Further, ΣI (HKL) is the total sum of X-ray diffraction intensities derived from each of the specific crystal planes (HKL) that are the measurement targets of the degree of orientation. The surface to be measured (HKL) when examining the orientation degree of the a-axis is (H00). (H00) means an a-plane such as (100) or (200) and a crystallographically equivalent crystal plane. P is a value measured for a piezoelectric substrate (sintered thin plate after finish polishing).₀Is a value measured for a natural surface, that is, a value measured for a sintered body (sintered body before polishing) having the same composition and orientation as the piezoelectric substrate.
[0040]
After the finish polishing, the center line average roughness Ra of the surface of the sintered compact sheet is preferably less than 0.27 μm, more preferably 0.15 μm or less. When Ra is large, the Q of the piezoelectric vibrator_maxWill become smaller. However, even if Ra is made extremely small,_maxTherefore, Ra does not need to be less than 0.06 μm. The center line average roughness Ra is defined in JIS B0601.
[0041]
The abrasive grain used in the final polishing process needs to be smaller than the abrasive grain used in the immediately preceding polishing process. The average particle size of the abrasive grains is preferably less than 6.7 μm, more preferably 1.2 to 5.5 μm. If the average grain size of the abrasive grains is too large, a new work-affected layer is generated in the final polishing process._maxWill become smaller. On the other hand, if the average particle size of the abrasive grains is too small, the polishing rate becomes slow, and thus the production efficiency is lowered. The constituent material of the abrasive grains is not particularly limited, but it is preferable to use white fused alumina because it is easy to precisely finish the polished surface.
[0042]
Processing / vibrating electrode formation process
In the machining / vibrating electrode forming step, the sintered thin plate is cut into a piezoelectric substrate so as to have a plane dimension suitable for the piezoelectric substrate of the piezoelectric vibrator. To obtain a piezoelectric vibrator. This process is the same as the conventional method for manufacturing a piezoelectric vibrator.
[0043]
【Example】
Based on the first aspect of the present invention, an example sample of a piezoelectric vibrator was manufactured by the following procedure.
[0044]
As a starting material, CaCO_Three, Bi₂O_ThreeTiO₂, La₂O_Three, MnCO_Three, Y₂O_ThreeEach powder of the final composition (Ca_0.9La_0.1) Bi_FourTi_FourO₁₅+ MnO + Y₂O_ThreeThen, it was wet-mixed for 16 hours by a ball mill using zirconia balls in pure water. (Ca_0.9La_0.1) Bi_FourTi_FourO₁₅MnO and Y against₂O_ThreeWas added at 0.43% by mass and 0.1% by mass, respectively.
[0045]
Next, the mixture was sufficiently dried and preformed, and then calcined in the air for 2 hours. The calcining temperature was 800 ° C. The obtained calcined product was coarsely pulverized with a mortar, and further pulverized with a rough machine. Subsequently, it was pulverized for 16 hours with a ball mill and then dried. Next, 6% by mass of pure water was added as a binder, and then temporary molding was performed at 49 MPa to obtain a molded body having a planar size of 20 mm × 20 mm and a thickness of 15 mm. The compact was vacuum packed and then molded by an isostatic press at a pressure of 296 MPa.
[0046]
The obtained molded body was fired. Firing was performed in a sealed container made of MgO in order to prevent evaporation of Bi. The firing temperature was 1200 ° C., and the firing time was 4 hours.
[0047]
The obtained sintered body was sliced to a thickness of 450 μm and then polished to a thickness of 250 μm by lapping to obtain a sintered body thin plate (primary polishing). The abrasive used for lapping is obtained by adding # 2000 abrasive grains (white fused alumina, average particle diameter of 6.7 μm) and a rust inhibitor to water.
[0048]
Next, temporary electrodes (Cu) were formed on the upper and lower surfaces of the sintered thin plate by vapor deposition. Next, polarization treatment was performed by applying an electric field of 15 MV / m for 5 minutes in a 200 ° C. silicone oil bath. Next, the temporary electrode was removed by etching using a ferric chloride solution.
[0049]
Next, the sintered thin plate was polished by lapping until the thickness became 150 μm (secondary polishing). The lapping conditions in the secondary polishing were the same as those in the primary polishing.
[0050]
Next, the sintered thin plate was polished by lapping until the thickness became 120 μm (finish polishing). The lapping conditions in the final polishing were the same as those in the primary polishing except that # 6000 abrasive grains (white fused alumina, average grain size 2.0 μm) were used instead of # 2000 abrasive grains.
[0051]
After finish polishing, the degree of orientation of the a-axis on the surface of the sintered compact sheet was measured by the procedure described above.
[0052]
Next, a piezoelectric substrate was obtained by cutting into a plane size of 7 mm × 4.5 mm so that the polarization direction was the thickness direction. Vibrating electrodes (Ag) for evaluating thickness longitudinal vibration were formed on the upper and lower surfaces of this piezoelectric substrate by vapor deposition. The dimensions of the vibrating electrode were a diameter of 0.4 mm and a thickness of 0.6 μm.
[0053]
Further, a comparative example sample of a piezoelectric vibrator was manufactured in the same manner as the example sample except that a piezoelectric substrate having a thickness of 120 μm was used by secondary polishing without performing final polishing. In the preparation of this comparative sample, the degree of orientation of the a-axis on the surface of the sintered thin plate was measured by the procedure described above after the secondary polishing.
[0054]
For each sample, Q impedance at 60 MHz in the third harmonic mode of thickness longitudinal vibration using Hewlett Packard Impedance Analyzer HP4194A._maxWas measured. As a result, Q_maxIs 6.7 for the example sample and 3.1 for the comparative example sample._maxWas found to be more than doubled.
[0055]
The degree of orientation of the a-axis on the surface of the sintered thin plate (polished surface) was 11.8% in the example sample after finish polishing, but 12.8% in the comparative example sample after secondary polishing. .
[0056]
The crystal of each sample is a quasi-tetragonal crystal, and the degree of orientation of the a-axis was determined using ΣI (H00). The only peak observed as (H00) in the X-ray diffraction pattern was (200). Also,
(PP₀) / (1-P₀* 100 (1)
Orientation degree P in the natural plane₀The degree of orientation in the sintered body before the primary polishing was used.
[0057]
The center line average roughness Ra of the surface of the sintered compact sheet (polished surface) was 0.11 μm in the example sample after finish polishing, but was 0.27 μm in the comparative example sample after secondary polishing. It was.
[0058]
In addition, although the effect in a 1st aspect was confirmed concretely above, although the piezoelectric vibrator sample produced based on the 2nd aspect also took a long time for manufacture, Q equivalent to the said Example sample is mentioned._maxwas gotten.
[0059]
The effects of the present invention are apparent from the results of the above examples.
[Brief description of the drawings]
1A is a process path diagram in the first embodiment of the present invention, FIG. 1B is a process path diagram in the second embodiment of the present invention, and FIG. 1C is a process in a conventional manufacturing method; It is a route diagram.
FIG. 2 is a cross-sectional view schematically showing a double-sided simultaneous lapping apparatus.
[Explanation of symbols]
2 Lower surface plate
3 Upper surface plate
4 Career
5 Workpiece
6 Abrasive grains

Claims (5)

A piezoelectric substrate containing a bismuth layered compound, and vibration electrodes respectively formed on both sides of the piezoelectric substrate ;
There is substantially no work-affected layer on the vibration electrode forming surface of the piezoelectric substrate,
In the vibration electrode forming surface of the piezoelectric substrate, the orientation degree of the a-axis of the bismuth layered compound is 11.5% or more and 12.0% or less,
The center line average roughness Ra of the piezoelectric substrate is 0.06 μm or more and 0.15 μm or less,
The bismuth layered compound contains M ^II (M ^II is an element selected from Sr, Ba and Ca), Bi, Ti, O and a lanthanoid oxide, and includes M ^II Bi ₄ Ti ₄ O ₁₅ type crystal, A piezoelectric vibrator having an atomic ratio Ln / (Ln + M ^II ) of 0.03 ≦ Ln / (Ln + M ^II ) ≦ 0.3 when the lanthanoid is represented by Ln . A method of manufacturing a piezoelectric vibrator having a piezoelectric substrate containing a bismuth layered compound and vibration electrodes formed on both sides of the piezoelectric substrate, the sintered body containing the bismuth layered compound being polished and sintered. A primary polishing step for obtaining a bonded thin plate, a polarizing step for forming a temporary electrode on the polished surface in the primary polishing step and performing a polarization treatment, and a temporary step for removing the temporary electrode, and forming a temporary electrode for the sintered thin plate Secondary polishing step for polishing the surface that has been used, and final polishing for polishing the polishing surface in the secondary polishing step by 1 μm or more in thickness using abrasive grains having a particle size smaller than that used in the secondary polishing step A method for manufacturing a piezoelectric vibrator, comprising: a step; and a step of forming a vibrating electrode on a polished surface in a final polishing step. A method of manufacturing a piezoelectric vibrator having a piezoelectric substrate containing a bismuth layered compound and vibration electrodes formed on both sides of the piezoelectric substrate, the sintered body containing the bismuth layered compound being polished and sintered. A primary polishing step for obtaining a bonded thin plate, a polarization step for forming a temporary electrode on the polished surface in the primary polishing step and performing a polarization treatment, and then removing the temporary electrode, and abrasive grains used in the primary polishing step A polishing electrode is formed on the polished surface in the final polishing step and a final polishing step in which the surface on which the temporary electrode of the sintered thin plate is formed is polished by 1 μm or more by using abrasive grains having a smaller particle size A method of manufacturing a piezoelectric vibrator having a process. Wherein the finish polishing step, the piezoelectric vibrator manufacturing method according to claim 2 or 3 using abrasive grains having an average grain size of 1.2～5.5Myuemu. The piezoelectric vibrator according to any one of claims 2 to 4 , wherein in the final polishing step, the bismuth layered compound on the surface of the sintered compact is polished so that the degree of orientation of the a-axis is 11.5% or more and 12.0% or less. Manufacturing method.

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