JP2005187223A - Raw material powder for piezoelectric ceramic, piezoelectric ceramic and production method therefor, and piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic having a large Q<SB>max</SB>in a fundamental wave mode of thickness-shear vibration, e.g., a fundamental wave mode of thickness-shear vibration at 8 MHz, and to provide a piezoelectric device, such as a resonator, having the piezoelectric ceramic as a piezoelectric body. <P>SOLUTION: The raw material powder for the piezoelectric ceramic contains, as a main component, a bismuth layered compound including an M<SP>II</SP>Bi<SB>4</SB>Ti<SB>4</SB>O<SB>15</SB>type crystal (wherein, M<SP>II</SP>is elements constituted of Ba, Sr and Ln (where Ln is a lanthanoid element)), containing at least Ba, Sr, Ln, Bi, Ti and O, and as a sub-component, oxides of each element of Mn and Ge and/or compounds being converted into these oxides after being fired. In the raw material powder, 50% diameter (D50 diameter) in cumulative number-size distribution is 0.5-1.4 μm. The piezoelectric ceramic is produced by using the raw material powder for the piezoelectric ceramic. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a piezoelectric ceramic raw material powder containing a bismuth layered compound, a piezoelectric ceramic using the piezoelectric ceramic raw material powder and a manufacturing method thereof, and further to a piezoelectric element such as a resonator using the piezoelectric ceramic as a piezoelectric body.

  Piezoelectric ceramics are materials that have a piezoelectric effect in which electrical polarization changes when stress is applied from the outside, and an inverse piezoelectric effect in which distortion occurs when an electric field is applied. Piezoelectric ceramics are widely used not only in the field of electronic devices such as resonators and filters, but also in products that use electric charges and displacement, such as sensors and actuators.

Most of the piezoelectric ceramics currently in practical use have a perovskite structure such as a tetragonal or rhombohedral PZT (PbZrO ₃ —PbTiO ₃ solid solution) system or a tetragonal PT (PbTiO ₃ ) system. Ferroelectric materials are common. And various subcomponents are added to these, and the response | compatibility to various required characteristics is aimed at.

  However, PZT-based and PT-based piezoelectric ceramics often have a Curie point of about 200 to 400 ° C. in a practical composition, and become a paraelectric material at a temperature higher than that to lose piezoelectricity. Therefore, it cannot be applied to applications that are used at high temperatures, such as reactor control sensors.

  The PZT-based and PT-based piezoelectric ceramics contain a relatively large amount of lead oxide (PbO) of about 60 to 70% by mass. This lead oxide is highly volatile even at low temperatures and is environmentally friendly. Is also not preferable.

In order to solve the above problems, piezoelectric ceramics containing a bismuth layered compound have been proposed as piezoelectric ceramics having a high Curie point and not containing lead oxide (for example, Patent Documents 1 to 3). Patent Document 1 discloses a piezoelectric ceramic (piezoelectric ceramics) containing BaBi ₄ Ti ₄ O ₁₅ as a main crystal phase and containing a sub-crystal phase composed of a complex oxide of Ba and Ti in an amount of 4 to 30 mol% in the total weight. Is disclosed. Patent Document 2 discloses a piezoelectric ceramic containing a bismuth layered compound containing SrBi ₄ Ti ₄ O ₁₅ type crystal containing Sr, Bi, Ti and Ln (lanthanoid) and a Mn oxide. Patent Document 3 contains M ^II (M ^II is an element selected from Sr, Ba and Ca), Bi, Ti and O, and a bismuth layered compound containing M ^II Bi ₄ Ti ₄ O ₁₅ type crystal. A piezoelectric ceramic is disclosed.

On the other hand, since a resonator, which is one of piezoelectric elements, is used as an inductor, a piezoelectric ceramic used as a piezoelectric body of the resonator is required to have a large _Qmax . Q _max is tan θ _max when the maximum value of the phase angle is θ _max . 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.

However, although the piezoelectric ceramic disclosed in Patent Document 1 has improved the electromechanical coupling coefficient kr, it has insufficient Q _max and has piezoelectric characteristics that can be used as a piezoelectric body of a resonator. It ’s hard to say. Piezoelectric ceramics disclosed in Patent Document 2, although Q _max is large, the Q _max is Q _max of the fundamental mode of the thickness longitudinal vibration, as the piezoelectric ceramics using thickness shear vibration, sufficient piezoelectric Characteristics have not been obtained.

In Patent Document 3, a piezoelectric ceramic having a relatively high Q _max in the fundamental mode of thickness shear vibration is obtained. From the viewpoint of improving the performance of the resonator, Q _{max in} the fundamental wave mode of thickness shear vibration is obtained. Further improvement is demanded.

JP 2000-159574 A JP 2000-143340 A JP 2001-192267 A

An object of the present invention is to provide a piezoelectric ceramic raw material powder for obtaining a piezoelectric ceramic having a large Q _max in a fundamental wave mode of thickness shear vibration, for example, a fundamental wave mode of thickness shear vibration at 4 to 12 MHz, particularly 8 MHz, and the piezoelectric A piezoelectric ceramic manufactured using a ceramic raw material powder and a method for manufacturing the piezoelectric ceramic are provided. Another object of the present invention is to provide a piezoelectric element such as a piezoelectric ceramic resonator having such a piezoelectric ceramic as a piezoelectric body.

  The inventors of the present invention can achieve the object of the present invention by setting the 50% diameter (D50 diameter) in the number cumulative distribution to 0.5 to 1.4 μm in the piezoelectric ceramic raw material powder having a predetermined composition. The headline and the present invention have been completed.

That is, the piezoelectric ceramic raw material powder according to the present invention is
At least Ba, Sr, Ln (where Ln is a lanthanoid element), Bi, Ti, and O, and M ^II Bi ₄ Ti ₄ O ₁₅ type crystal (M ^II is an element composed of Ba, Sr, and Ln) The main component is a bismuth layered compound containing
As an accessory component, an oxide of Mn and / or a compound that becomes an oxide of Mn after firing and a compound that becomes an oxide of Ge and / or an oxide of Ge after firing are contained,
The 50% diameter (D50 diameter) in the number cumulative distribution is 0.5 to 1.4 μm.

In the present invention, the M ^II Bi ₄ Ti ₄ O ₁₅ type crystal (M ^II is an element composed of Ba, Sr and Ln) may have any composition in the vicinity of M ^II Bi ₄ Ti ₄ O ₁₅ , and it is You may do it. For example, the ratio of Bi to Ti is may be slightly deviated from the stoichiometric composition, Ba considered to be mainly replaced the M ^II site, Sr and Ln is partially replace other sites May be.

The piezoelectric ceramic raw material powder of the present invention is mainly composed of a bismuth layered compound containing M ^II Bi ₄ Ti ₄ O ₁₅ type crystal, and is preferably substantially composed of this crystal, but is completely homogeneous. For example, a different phase may be included.

In the piezoelectric ceramic material powder according to the present invention, preferably, the ^M II _Bi 4 _Ti 4 _{O 15} type crystal is represented by a composition formula _{(Ba 1-x over y Sr x Ln y) Bi z} Ti 4 O 15 In the composition formula, x is 0.1 ≦ x ≦ 0.6, y is 0.05 ≦ y ≦ 0.5, and z is 3.90 ≦ z ≦ 4.30.

In the piezoelectric ceramic raw material powder according to the present invention, preferably, the content of the Mn oxide and / or the compound that becomes an Mn oxide after firing is 0.1 to 1.0% by weight in terms of MnO. The content of the Ge oxide and / or the compound that becomes Ge oxide after firing is 0.05 to 0.5% by weight in terms of GeO ₂ .

The method for manufacturing a piezoelectric ceramic according to the present invention includes:
As the main component material, at least Ba, Sr, Ln (where Ln is a lanthanoid element), Bi and Ti oxides of each element and / or compounds that become these oxides after firing,
Mixing and calcination of oxides of each element of Mn and Ge and / or compounds that become these oxides after firing as subcomponent raw materials,
Bismuth layered compound containing M ^II Bi ₄ Ti ₄ O ₁₅ type crystal (M ^II is an element composed of Ba, Sr and Ln) and oxide of each element of Mn and Ge and / or oxide after firing Obtaining a calcined product containing the compound;
Pulverizing the calcined product so that the 50% diameter (D50 diameter) in the number cumulative distribution is 0.5 to 1.4 μm to obtain a piezoelectric ceramic raw material powder;
Firing the piezoelectric ceramic raw material powder.

In the manufacturing method of the piezoelectric ceramic according to the present invention, the table preferably, the ^M II _Bi 4 _Ti 4 _{O 15} type crystals, composition formula _{(Ba 1-x over y Sr x Ln y) Bi z} Ti 4 O 15 X in the composition formula is 0.1 ≦ x ≦ 0.6, y is 0.05 ≦ y ≦ 0.5, and z is 3.90 ≦ z ≦ 4.30.

In the method for producing a piezoelectric ceramic according to the present invention, preferably, the content of the Mn oxide and / or the compound that becomes an Mn oxide after firing is 0.1 to 1.0% by weight in terms of MnO. In addition, the content of the Ge oxide and / or the compound that becomes a Ge oxide after firing is 0.05 to 0.5% by weight in terms of GeO ₂ .

  In the method for manufacturing a piezoelectric ceramic according to the present invention, the firing temperature in the firing step is preferably 1000 to 1200 ° C.

  The piezoelectric ceramic according to the present invention is manufactured by any one of the methods described above.

  The piezoelectric element according to the present invention has a piezoelectric body made of the above-described piezoelectric ceramic. Although it does not specifically limit as a piezoelectric element, A piezoelectric ceramic resonator, a filter, a sensor, an actuator, etc. are illustrated.

In the piezoelectric element according to the present invention, preferably, Q (Q = | X | / R; X is reactance, R is resistance) between the resonance frequency and the antiresonance frequency with respect to the fundamental wave of thickness shear vibration at 8 MHz. The maximum value Q _max is 23 or more, more preferably 25 or more.

Q _max is tan θ _max when the maximum value of the phase angle is θ _max . 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. As Q _max is larger, the oscillation becomes more stable, and oscillation at a low voltage is possible.

According to the present invention, the piezoelectric ceramic raw material powder is a piezoelectric ceramic raw material powder containing a bismuth layered compound and having a 50% diameter (D50 diameter) of 0.5 to 1.4 μm in the number cumulative distribution. Piezoelectric ceramics having a large _Qmax in the fundamental mode of sliding vibration can be provided. In addition, according to the present invention, it is possible to provide a method for manufacturing such a piezoelectric ceramic and a piezoelectric element such as a resonator having such a piezoelectric ceramic as a piezoelectric body.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a perspective view of a piezoelectric ceramic resonator according to an embodiment of the present invention.
FIG. 2 is a sectional view of a piezoelectric ceramic resonator according to an embodiment of the present invention.
FIG. 3 is a graph showing the relationship between the D50 diameter and Q _max of the piezoelectric ceramic raw material powder of Example 1 in the Example of the present invention;
FIG. 4 is a graph showing the relationship between the D50 diameter and Q _max of the piezoelectric ceramic raw material powder of Example 2 in the Example of the present invention;
FIG. 5 is a graph showing the relationship between the D50 diameter and Q _max of the piezoelectric ceramic raw material powder of Example 3 in the Example of the present invention;
FIG. 6 is a graph showing the relationship between the D50 diameter and Q _max of the piezoelectric ceramic raw material powder of Example 4 in the example of the present invention.

Piezoelectric Ceramic Resonator As shown in FIGS. 1 and 2, a piezoelectric ceramic resonator 1 according to an embodiment of the present invention includes a resonator element body 10 having a configuration in which a piezoelectric layer 2 is sandwiched between two vibration electrodes 3. . As shown in FIG. 1, the vibration electrode 3 is formed at the center of the upper surface of the piezoelectric layer 2 and is also formed on the lower surface. Although there is no restriction | limiting in particular in the shape of the resonator element main body 10, Usually, it is set as a rectangular parallelepiped shape. Moreover, there is no restriction | limiting in particular also in the dimension, What is necessary is just to set it as a suitable dimension according to a use, Usually, length 1.5-7.5 mm x width 0.5-3.5 mm x height 0.08- It is about 0.35 mm.

  The piezoelectric layer 2 contains a main component containing a bismuth layered compound and at least a Mn oxide and a Ge oxide as subcomponents. The bismuth layered compound has a layered structure in which a pseudo-perovskite structure layer is sandwiched between a pair of Bi and O layers.

The bismuth layered compound contains at least Ba, Sr, Ln (where Ln is a lanthanoid element), Bi, Ti and O, and M ^II Bi ₄ Ti ₄ O ₁₅ type crystal (M ^II is Ba, Sr and Ln). Element). M ^II Bi ₄ Ti ₄ O ₁₅ type crystal is preferably represented by the composition formula _{(Ba 1-x over y Sr x Ln y) Bi z} Ti 4 O 15. In the present invention, the amount of oxygen (O) may be slightly deviated from the stoichiometric composition of the above formula.

X in the composition formula is preferably 0.1 ≦ x ≦ 0.6, and more preferably 0.2 ≦ x ≦ 0.5. x represents the number of atoms of Sr. If the value of x is too small, the sinterability becomes unstable and large voids are formed, and Q _max tends to decrease. If it is too large, Q _max tends to decrease and temperature characteristics tend to deteriorate. is there.

Y in the composition formula is preferably 0.05 ≦ y ≦ 0.5, and more preferably 0.1 ≦ y ≦ 0.3. y represents the number of atoms of Ln. Ln _is an effect of improving the _{Q max.} Here, Ln represents a lanthanoid element, and the lanthanoid elements are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Among these, at least one element selected from La, Gd, Sm, Nd and Yb is particularly preferable. If the value of y is too small, Q _max tends to be low. Similarly, if it is too large, Q _max tends to be low.

Z in the composition formula is preferably 3.90 ≦ z ≦ 4.30, and more preferably 4.00 ≦ z ≦ 4.15. z represents the number of atoms of Bi. By setting z within the above range, the mechanical quality factor (Q _m ) can be improved. If the value of z is too small, the sinterability tends to deteriorate and Q _max tends to decrease. If it is too large, the electrical resistance decreases, so that polarization becomes difficult and Q _max tends to decrease.

The content of the Mn oxide is preferably 0.1 to 1.0% by weight, more preferably 0.2 to 0.7% by weight in terms of MnO. When the content of the Mn oxide is too small, Q _max tends to be low, and when it is too large, the insulation resistance is lowered and polarization tends to be difficult.

The content of Ge oxide is preferably 0.05 to 0.5% by weight, more preferably 0.1 to 0.3% by weight in terms of GeO ₂ . When the content of the Ge oxide is too small, the sinterability tends to be lowered, and when it is too much, Q _max tends to be lowered.

  In addition, the piezoelectric layer 2 contains compounds other than those described above, such as oxides of Ca, Sn, Mo, W, Y, Zn, Sb, Si, Nb, and Ta, as impurities or trace additives. It may be contained. In addition, it is preferable that content in this case is 0.01 weight% or less of the whole piezoelectric ceramic in conversion of the oxide of each element.

  The thickness of the piezoelectric layer 2 is not particularly limited, but is usually about 80 to 350 μm.

  The conductive material contained in the vibrating electrode 3 is not particularly limited, but, for example, Ag can be used. Further, the shape of the vibrating electrode 3 is not particularly limited, but in the present embodiment, it is preferably a circular shape with a diameter of about 0.5 to 3.0 mm, and the thickness is usually about 1 to 8 μm.

Manufacturing Method of Piezoelectric Ceramic Resonator The piezoelectric ceramic resonator 1 of the present embodiment is made by granulating the piezoelectric ceramic raw material powder of the present invention, then press-molding and firing to produce a piezoelectric layer, and polarizing the piezoelectric layer. Then, it is manufactured by forming a vibrating electrode by a vacuum deposition method or a sputtering method. Hereinafter, the manufacturing method will be specifically described.

First, a piezoelectric ceramic raw material powder is prepared.
The piezoelectric ceramic raw material powder of this embodiment is obtained by mixing and calcining the main component raw material and the subcomponent raw material, and then finely pulverizing the 50% diameter (D50 diameter) to 0.5 to 1.4 μm in the number cumulative distribution. It is manufactured by doing. The manufacturing method of the piezoelectric ceramic raw material powder is as follows.

  First, a main component material and a subcomponent material that are starting materials are prepared. As the main component material, oxides of elements constituting the bismuth layered compound and / or compounds that become these oxides after firing can be used. As the subcomponent raw materials, the oxides of the subcomponents described above and / or compounds that become these oxides after firing can be used. Examples of the compound that becomes an oxide after firing include carbonates, hydroxides, oxalates, nitrates, and the like. The average particle size of each main component material and subcomponent material is preferably 1.0 to 5.0 μm.

  Next, the main component material and the subcomponent material are wet-mixed by a ball mill or the like.

Next, the raw material powder that has been wet-mixed is temporarily molded as necessary and calcined to obtain a calcined product. In the present embodiment, the calcined product includes a bismuth layered compound containing M ^II Bi ₄ Ti ₄ O ₁₅ type crystal (M ^II is an element composed of Ba, Sr, and Ln), and each element of Mn and Ge. It contains oxides and / or compounds that become these oxides after firing.

  As the calcination conditions, the calcination temperature is preferably 700 to 1000 ° C., more preferably 750 to 850 ° C., and the calcination time is preferably about 1 to 3 hours. If the calcining temperature is too low, the chemical reaction tends to be insufficient, and if the calcining temperature is too high, the calcined body starts to sinter, so that subsequent pulverization tends to be difficult. The calcination may be performed in the air, or may be performed in an atmosphere having a higher oxygen partial pressure or in a pure oxygen atmosphere than in the air.

  Next, the calcined product obtained by calcining is made into a slurry, finely pulverized, and then dried to obtain a piezoelectric ceramic raw material powder. The fine pulverization can be performed by wet pulverization using, for example, a ball mill. At this time, it is preferable to use water or an alcohol such as ethanol or a mixed solvent of water and ethanol as a solvent for the slurry.

In this embodiment, the 50% diameter (D50 diameter) in the number cumulative distribution of the piezoelectric ceramic raw material powder obtained by fine pulverization is 0.5 to 1.4 μm, preferably 0.6 to 1.2 μm, and more preferably. 0.8 to 1.0 μm. In addition, the 50% diameter (D50 diameter) in the number cumulative distribution of the piezoelectric ceramic raw material powder can be measured by, for example, a laser diffraction method. If the D50 diameter of the piezoelectric ceramic raw material powder is too small, Q _max tends to decrease, and if it is too large, Q _max tends to decrease.

The feature of the present invention is that the 50% diameter (D50 diameter) in the number cumulative distribution of the piezoelectric ceramic raw material powder is within the above range, and in this way, the basis of the thickness-shear vibration of the sintered piezoelectric ceramic. Q _max in the wave mode can be increased.

The reason why the _Qmax in the fundamental mode of thickness shear vibration can be increased by setting the D50 diameter in the above range is not necessarily clear, but the particle diameter of the sintered body after firing, This is probably because the balance with the pores in the body is improved.

  Next, a binder is added to the piezoelectric ceramic raw material powder obtained above as necessary, granulated, and then press-molded to obtain a compact. Examples of the binder include commonly used organic binders such as polyvinyl alcohol, polyvinyl alcohol added with a dispersant, and ethyl cellulose. Moreover, the load at the time of press molding can be 100-400 MPa, for example.

  Subsequently, a binder removal process is performed about a molded object. This binder removal treatment is preferably performed at a temperature of 300 to 700 ° C. for about 0.5 to 5 hours. The binder removal treatment may be performed in the air, or may be performed in an atmosphere having a higher oxygen partial pressure than in the air or a pure oxygen atmosphere.

After the binder removal treatment, firing is performed to obtain a sintered body of piezoelectric ceramic. As firing conditions, the firing temperature is preferably 1000 to 1200 ° C., more preferably 1050 to 1150 ° C., and the firing time is preferably about 1 to 3 hours. If the firing temperature is too low, the sintering tends to be insufficient, and if the firing temperature is too high, Bi evaporates, resulting in a composition shift and pore enlargement, and Q _max tends to decrease. Firing may be performed in the air, or may be performed in an atmosphere having a higher oxygen partial pressure than in the air or a pure oxygen atmosphere.

  The binder removal step and the firing step may be performed continuously or separately.

  Next, the sintered body of the piezoelectric ceramic obtained by firing is cut into a thin plate shape to form a sintered body thin plate, and surface processing is performed by lapping. When the sintered body is cut, a cutting machine such as a cutter, a slicer, or a dicing saw can be used.

  Next, a temporary electrode for polarization treatment is formed on both surfaces of the thin plate-like sintered body. Although the electrically conductive material which comprises a temporary electrode is not specifically limited, Since it can remove easily by the etching process by a ferric chloride solution, Cu is preferable. For forming the temporary electrode, it is preferable to use a vacuum deposition method or sputtering.

  Next, polarization treatment is performed on the thin plate-like sintered body on which the temporary electrode for polarization treatment is formed. The conditions for the polarization treatment may be appropriately determined according to the composition of the piezoelectric ceramics. Usually, the polarization temperature is 150 to 300 ° C., the polarization time is 1 to 30 minutes, and the polarization electric field is 1. What is necessary is just to make it 1 time or more.

Next, the temporary electrode is removed from the sintered body subjected to the polarization treatment by an etching treatment or the like, and cut into a desired element shape to form the vibrating electrode 3. Although it does not specifically limit as a electrically conductive material which comprises the vibration electrode 3, Ag etc. can be used. For the formation of the vibrating electrode, it is preferable to use vacuum deposition or sputtering.
In this way, the piezoelectric ceramic resonator of the present embodiment is manufactured.

In this embodiment, a piezoelectric ceramic raw material powder having a D50 diameter of 0.5 to 1.4 μm, preferably 0.6 to 1.2 μm is used as a piezoelectric raw material constituting the piezoelectric ceramic resonator. A piezoelectric ceramic resonator having Q _max can be obtained. In this embodiment, since such a piezoelectric material is used, the Q _max in the fundamental wave mode of the thickness shear vibration at 8 MHz can be preferably 23 or more, and more preferably 25 or more. The reason why the measurement frequency is set to 8 MHz is to deal with in-vehicle IC control, AV device controller IC, and the like.

In the present embodiment, the Q _max in the fundamental wave mode of the thickness shear vibration at 8 MHz has been described. However, the piezoelectric element of the present invention has a large Q _max even in a frequency band of about 4 to 12 MHz. It can be suitably used even in a frequency band of about 12 MHz. According to the present invention, for example, the Q _max at about 4 to 6 MHz can be preferably 17 or more, and the Q _max at about 10 to 12 MHz can be preferably 23 or more.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the embodiment mentioned above at all, and can be variously modified within the range which does not deviate from the summary of this invention.

  For example, in the above-described embodiment, the piezoelectric ceramic resonator is exemplified as the piezoelectric element according to the present invention. However, the piezoelectric element according to the present invention is not limited to the piezoelectric ceramic resonator, and is manufactured using the piezoelectric ceramic raw material powder. Any material may be used as long as it has a piezoelectric layer made of piezoelectric ceramic.

  In the above-described embodiment, the addition time of the subcomponent raw material is the same as that of the main component raw material, but it is also possible to add the subcomponent raw material after reacting the main component raw material in advance to obtain a reaction product.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
Main component raw materials BaCO ₃ , SrCO ₃ , La ₂ O ₃ , Bi ₂ O ₃ , TiO ₂ , and subcomponent raw materials MnO and GeO ₂ are prepared. (Ba _0.6 Sr _0.3 La _0.1 ) Bi _4.033 Ti ₄ O _{15 The} subcomponent raw material MnO has a content of 0.3% by weight and GeO ₂ has a content of 0. Each was weighed to 15% by weight. Next, pure water was added and mixed for 16 hours in a ball mill containing zirconia media in pure water, followed by sufficient drying to obtain a mixed powder.

  The obtained mixed powder was temporarily molded and calcined in air at 850 ° C. for 2 hours to prepare a calcined product. Next, pure water was added to the obtained calcined material, finely pulverized in a ball mill containing zirconia media in pure water, and dried to prepare a piezoelectric ceramic raw material powder. In the fine pulverization, piezoelectric ceramic raw material powders having different particle diameters (D50 diameters) were obtained by changing the pulverization time and pulverization conditions. In addition, the particle diameter (D50 diameter) of each piezoelectric ceramic raw material powder was calculated | required by performing 50% diameter in a number integration distribution by the laser beam diffraction method.

  After adding 6% by weight of pure water as a binder to each piezoelectric ceramic raw material powder having a different particle size, press molding to form a temporary molded body of 40 mm length × 40 mm width × 13 mm thickness, and after vacuum packing this temporary molded body Molding was performed by a hydrostatic press at a pressure of 245 MPa.

  Next, the molded body was fired at 1100 ° C. to obtain a sintered body. Next, after cutting this sintered body, surface processing was performed by lapping to obtain a length of 30 mm × width of 30 mm × thickness of 0.25 mm.

  A Cu electrode for polarization treatment is formed on both surfaces of the sintered body cut as described above by vacuum deposition, and an electric field of 1.5 × Ec (MV / m) or more is applied in a 250 ° C. silicon oil bath. Applying for minutes, polarization treatment was performed. Ec is a coercive electric field of each sintered body at 250 ° C.

  Next, the Cu electrode is removed by etching using a ferric chloride solution from the sintered body subjected to the polarization treatment, and then the sintered body is lapped again, length 4.5 mm × width 2.0 m × thickness A 0.25 mm piezoelectric ceramic sample was obtained.

  An Ag electrode having a diameter of 1.4 mm and a thickness of 1 μm was formed in the center of both surfaces of this piezoelectric ceramic sample by vacuum deposition, and a piezoelectric ceramic resonator sample produced using piezoelectric ceramic raw material powders having different particle diameters was obtained. .

Measurement of Q _{max Using} the impedance analyzer (HP4194A manufactured by Hewlett-Packard Co., Ltd.) and measuring the impedance characteristics in the fundamental wave mode of thickness shear vibration (8 MHz) for the piezoelectric ceramic sample prepared above, Q _max was determined.

FIG. 3 is a graph showing the relationship between the D50 diameter of the used ceramic raw material powder and Q _max in the fundamental wave mode of the thickness shear vibration of the piezoelectric ceramic resonator sample in the piezoelectric ceramic resonator sample manufactured in this example. . From FIG. 3, the value of _Qmax increases as the D50 diameter increases until the D50 diameter is about 0.9 μm. However, when the D50 diameter is larger than about 0.9 μm, the D50 diameter increases. Along with this, it was confirmed that the Q _max value tends to decrease. In a sample in which the D50 diameter of the ceramic raw material powder was 0.5 to 1.4 μm, Q _max exceeded 23, and a good result was obtained. Among them, in the sample in which the D50 diameter of the ceramic raw material powder and _{0.8~1.1μm, Q max} exceeds 30, it was a particularly good result.

From this result, even if the 50% diameter (D50 diameter) in the number cumulative distribution of the ceramic raw material powder used as the raw material of the piezoelectric layer of the piezoelectric ceramic resonator is too small or too large, Q _max tends to be small. I was able to confirm. Therefore, the D50 diameter is desirably 0.5 to 1.4 μm, and preferably 0.6 to 1.2 μm.

Example 2
Except that by changing the ratio of Ba and Sr in the final composition of the main component of the piezoelectric ceramic material powder to a final composition as _{(Ba 0.4 Sr 0.5 La 0.1)} Bi 4.033 Ti 4 O 15 is In the same manner as in Example 1, piezoelectric ceramic raw material powders having different particle diameters were produced, and piezoelectric ceramic resonator samples were produced using the respective piezoelectric ceramic raw material powders.

FIG. 4 is a graph showing the relationship between the D50 diameter of the ceramic raw material powder used and the Q _max in the fundamental wave mode of the thickness shear vibration of the piezoelectric ceramic resonator sample in the piezoelectric ceramic resonator sample manufactured in this example. .

From FIG. 4, when the ratio of Ba and Sr is changed, and the ceramic raw material powder whose main component composition is (Ba _0.6 Sr _0.3 La _0.1 ) Bi _4.033 Ti ₄ O ₁₅ is used. also, in the same manner as in example 1, D50 diameter is the value of the even Q _max too large or too small, it was confirmed that tends to decrease.

Example 3
Gd ₂ O ₃ is used instead of La ₂ O ₃ as the main component material, and the final composition of the main component of the piezoelectric ceramic material powder is (Ba _0.6 Sr _0.3 Gd _0.1 ) Bi _4.033 Ti. _A piezoelectric ceramic raw material powder having a different particle diameter was prepared in the same manner as in Example 1 except that ₄ O ₁₅ was used, and a piezoelectric ceramic resonator sample was prepared using each piezoelectric ceramic raw material powder.

FIG. 5 is a graph showing the relationship between the D50 diameter of the ceramic raw material powder used and the Q _max in the fundamental wave mode of the thickness shear vibration of the piezoelectric ceramic resonator sample in the piezoelectric ceramic resonator sample manufactured in this example. .

From FIG. 5, each piezoelectric ceramic resonator sample of Example 3 using a ceramic raw material powder whose main component composition is (Ba _0.6 Sr _0.3 Gd _0.1 ) Bi _4.033 Ti ₄ O ₁₅ is as in example 1, 2, D50 diameter is the value of the even Q _max too large or too small, it was confirmed that tends to decrease.

Example 4
Piezoelectric ceramic raw material powders having different particle diameters were prepared in the same manner as in Example 2 except that the content of MnO as an auxiliary component raw material was 0.5% by weight, and each piezoelectric ceramic raw material powder was used to produce a piezoelectric ceramic resonator sample. Was made.

FIG. 6 is a graph showing the relationship between the D50 diameter of the used ceramic raw material powder and Q _max in the fundamental wave mode of the thickness shear vibration of the piezoelectric ceramic resonator sample in the piezoelectric ceramic resonator sample manufactured in this example. .

From FIG. 6, each piezoelectric ceramic resonator sample of Example 4 using a ceramic raw material powder whose main component composition is 0.5% by weight of MnO has a D50 diameter as in Examples 1-3. , the value of the even Q _max too large or too small, it was confirmed that tends to decrease.

FIG. 1 is a perspective view of a piezoelectric ceramic resonator according to an embodiment of the present invention. FIG. 2 is a sectional view of a piezoelectric ceramic resonator according to an embodiment of the present invention. FIG. 3 is a graph showing the relationship between the D50 diameter and Q _max of the piezoelectric ceramic raw material powder of Example 1 in the example of the present invention. FIG. 4 is a graph showing the relationship between the D50 diameter and Q _max of the piezoelectric ceramic raw material powder of Example 2 in the example of the present invention. FIG. 5 is a graph showing the relationship between the D50 diameter and Q _max of the piezoelectric ceramic raw material powder of Example 3 in the example of the present invention. FIG. 6 is a graph showing the relationship between the D50 diameter and Q _max of the piezoelectric ceramic raw material powder of Example 4 in the example of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric ceramic resonator 10 ... Resonator element body 2 ... Piezoelectric layer 3 ... Vibrating electrode

Claims (9)

At least Ba, Sr, Ln (where Ln is a lanthanoid element), Bi, Ti, and O, and M ^II Bi ₄ Ti ₄ O ₁₅ type crystal (M ^II is an element composed of Ba, Sr, and Ln) The main component is a bismuth layered compound containing
As an accessory component, an oxide of Mn and / or a compound that becomes an oxide of Mn after firing and a compound that becomes an oxide of Ge and / or an oxide of Ge after firing are contained,
A piezoelectric ceramic raw material powder having a 50% diameter (D50 diameter) in a number cumulative distribution of 0.5 to 1.4 μm. Wherein ^M II _Bi 4 _Ti 4 _{O 15} type crystal is represented by a composition formula _{(Ba 1-x over y Sr x Ln y) Bi z} Ti 4 O 15, x is 0.1 ≦ x ≦ in the composition formula The piezoelectric ceramic raw material powder according to claim 1, wherein 0.6, y is 0.05 ≦ y ≦ 0.5, and z is 3.90 ≦ z ≦ 4.30. The content of the Mn oxide and / or the compound that becomes the Mn oxide after firing is 0.1 to 1.0% by weight in terms of MnO,
3. The piezoelectric ceramic raw material powder according to claim 1, wherein a content of the Ge oxide and / or a compound that becomes a Ge oxide after firing is 0.05 to 0.5 wt% in terms of GeO ₂ . As the main component material, at least Ba, Sr, Ln (where Ln is a lanthanoid element), Bi and Ti oxides of each element and / or compounds that become these oxides after firing,
Mixing and calcination of oxides of each element of Mn and Ge and / or compounds that become these oxides after firing as subcomponent raw materials,
Bismuth layered compound containing M ^II Bi ₄ Ti ₄ O ₁₅ type crystal (M ^II is an element composed of Ba, Sr and Ln), oxides of each element of Mn and Ge and / or these oxides after firing Obtaining a calcined product containing a compound to be
Pulverizing the calcined product so that the 50% diameter (D50 diameter) in the number cumulative distribution is 0.5 to 1.4 μm to obtain a piezoelectric ceramic raw material powder;
A method for producing a piezoelectric ceramic, comprising a step of firing the piezoelectric ceramic raw material powder. Wherein ^M II _Bi 4 _Ti 4 _{O 15} type crystal is represented by a composition formula _{(Ba 1-x over y Sr x Ln y) Bi z} Ti 4 O 15, x is 0.1 ≦ x ≦ in the composition formula The method for manufacturing a piezoelectric ceramic according to claim 4, wherein 0.6, y is 0.05 ≦ y ≦ 0.5, and z is 3.90 ≦ z ≦ 4.30.   The method for producing a piezoelectric ceramic according to claim 4 or 5, wherein a firing temperature in the firing step is 1000 to 1200 ° C.   A piezoelectric ceramic manufactured by the method according to claim 4.   The piezoelectric element which has a piezoelectric material comprised with the piezoelectric ceramic of Claim 7. A maximum value Q _max of Q (Q = | X | / R; X is reactance, R is resistance) between a resonance frequency and an antiresonance frequency with respect to a fundamental wave of thickness shear vibration at 8 MHz is 23 or more. 9. The piezoelectric element according to 8.

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