JP4387135B2 - piezoelectric ceramic - Google Patents

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JP4387135B2
JP4387135B2 JP2003281359A JP2003281359A JP4387135B2 JP 4387135 B2 JP4387135 B2 JP 4387135B2 JP 2003281359 A JP2003281359 A JP 2003281359A JP 2003281359 A JP2003281359 A JP 2003281359A JP 4387135 B2 JP4387135 B2 JP 4387135B2
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bismuth
bismuth titanate
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直義 佐藤
正仁 古川
賢治 堀野
朋史 黒田
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Tdk株式会社
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  The present invention relates to a piezoelectric ceramic widely used in the field of actuators, sensors, resonators and the like.

Piezoelectric materials generate distortion by applying an electric field from the outside (conversion of electrical energy to mechanical energy), and generate charges on the surface by receiving external stress (to convert mechanical energy to electrical energy). In recent years, it has been widely used in various fields. For example, a piezoelectric material such as lead zirconate titanate (Pb (Zr, Ti) O 3 : PZT) generates a strain approximately proportional to the applied voltage in the order of 1 × 10 −10 m / V. It is excellent for fine position adjustment and is also used for fine adjustment of optical systems. On the other hand, the piezoelectric material generates a charge in proportion to the applied stress or the amount of deformation of the piezoelectric material, so that it is also used as a sensor for reading minute force and deformation. . Furthermore, since the piezoelectric material has excellent responsiveness, it is possible to cause resonance by exciting the piezoelectric material itself or an elastic body in a bonding relationship with the piezoelectric material by applying an alternating electric field. It is also used as a transformer and an ultrasonic motor.

Most of the piezoelectric materials currently in practical use are solid solution systems (PZT system) made of PbZrO 3 (PZ) -PbTiO 3 (PT). The reason is that excellent piezoelectric characteristics can be obtained by using a composition near the crystallographic phase boundary (MPB) of rhombohedral PZ and tetragonal PT. is there. A wide variety of PZT piezoelectric materials have been developed that meet various needs by adding various subcomponents or additives. For example, instead of a small mechanical quality factor (Qm), the piezoelectric constant (d) is large, and since the piezoelectric constant (d) is used for a position adjusting actuator or the like that requires a large amount of displacement by DC usage, the piezoelectric constant (d) There are various types, including a mechanical quality factor (Qm) that is large instead of a small one, and suitable for use in an alternating manner such as an ultrasonic generator such as an ultrasonic motor.

In addition to PZT materials, there are materials that have been put to practical use as piezoelectric materials, but they also have lead-based perovskite compositions such as lead magnesium niobate (Pb (Mg, Nb) O 3 : PMN) as the main component. Most are solid solutions.

  However, these lead-based piezoelectric materials contain a large amount of lead oxide (PbO) having a very high volatility at a low temperature of about 60 to 70% by mass as a main component. For example, in PZT or PMN, about 2/3 by mass is lead oxide. Therefore, when manufacturing these piezoelectric materials, an extremely large amount of lead oxide is volatilized and diffused in the atmosphere at an industrial level in a heat treatment process such as a firing process for porcelain and a melting process for single crystal products. End up. In addition, it is possible to recover the lead oxide released in the manufacturing stage. However, it is difficult to recover the lead oxide contained in the piezoelectric products put on the market as industrial products. When released to the sea, there is a concern about lead elution due to acid rain. Accordingly, if the application fields of piezoelectric ceramics and single crystals are expanded in the future, and the amount of use increases, the problem of lead-free becomes a very important issue.

Known piezoelectric materials containing no lead include, for example, barium titanate (BaTiO 3 ) or bismuth layered ferroelectrics. However, barium titanate has a Curie point as low as 120 ° C., and the piezoelectricity disappears above that temperature, so it is not practical when considering applications such as soldering or in-vehicle use. On the other hand, a bismuth layered ferroelectric usually has a Curie point of 400 ° C. or higher and is excellent in thermal stability, but has a large crystal anisotropy, so that spontaneous polarization is oriented by hot forging or the like. There is a problem in terms of productivity. Moreover, it is difficult to obtain large piezoelectricity if the lead content is completely eliminated.

Furthermore, recently, research has been conducted on a new material, sodium bismuth titanate material. For example, Patent Literature 1 and Patent Literature 2 disclose a material containing sodium bismuth titanate and barium titanate, and Patent Literature 3 discloses a material containing sodium bismuth titanate and potassium bismuth titanate. Has been.
Japanese Patent Publication No. 4-60073 JP-A-11-180769 Japanese Patent Application Laid-Open No. 11-171643

  However, these sodium bismuth titanate-based materials have not yet obtained sufficient piezoelectric characteristics as compared with lead-based piezoelectric materials, and improvement of the piezoelectric characteristics has been demanded.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a piezoelectric ceramic that exhibits excellent piezoelectric characteristics and is excellent in terms of low pollution, environmental friendliness, and ecology.

A first piezoelectric ceramic according to the present invention includes a first compound containing sodium bismuth titanate having a rhombohedral perovskite structure, a second compound containing potassium bismuth titanate having a tetragonal perovskite structure, and bismuth. (Bi), at least one divalent metal element selected from the group consisting of magnesium (Mg), iron (Fe), cobalt (Co), copper (Cu) and zinc (Zn), and titanium (Ti), It contains at least one tetravalent metal element selected from the group consisting of zirconium (Zr) and tin (Sn) and a third compound containing oxygen (O).

A second piezoelectric ceramic according to the present invention includes a first compound containing sodium bismuth titanate having a rhombohedral perovskite structure, a second compound containing potassium bismuth titanate having a tetragonal perovskite structure, and bismuth. (Bi), at least one divalent metal element selected from the group consisting of magnesium (Mg), iron (Fe), cobalt (Co), copper (Cu) and zinc (Zn), and titanium (Ti), The solid solution contains at least one tetravalent metal element selected from the group consisting of zirconium (Zr) and tin (Sn) and a third compound containing oxygen (O).

  In these piezoelectric ceramics according to the present invention, the content of lead (Pb) is preferably 1% by mass or less from the viewpoint of low pollution, environmental friendliness and ecological viewpoint. The composition ratio of the first compound, the second compound, and the third compound is such that the molar ratio of the first compound is x, the molar ratio of the second compound is y, and the molar ratio of the third compound. When the ratio is z, x, y and z are values within the ranges satisfying x + y + z = 1, 0.35 ≦ x ≦ 0.99, 0 <y ≦ 0.55, 0 <z ≦ 0.1, respectively. Preferably there is.

  In addition, the molar ratio of sodium bismuth titanate is α1, the molar ratio of potassium bismuth titanate is β1, and the composition ratio by the total molar ratio of sodium (Na) and bismuth to titanium (Ti) in sodium bismuth titanate is s1. When the composition ratio of the total molar ratio of potassium (K) and bismuth with respect to titanium in potassium bismuth titanate is t1, there is a relationship of α1 + β1 = 1, 0.9 ≦ α1s1 + β1t1 ≦ 1.0. Is preferred.

According to the first or second piezoelectric ceramic of the present invention, in addition to the first compound and the second compound, bismuth and at least one member selected from the group consisting of magnesium, iron, cobalt, copper and zinc are used. To contain a third compound containing a divalent metal element, at least one tetravalent metal element in the group consisting of titanium, zirconium and tin, and oxygen, or to contain a solid solution containing these Therefore, the piezoelectric characteristics such as the displacement amount can be improved. Therefore, it is possible to increase the possibility of using a piezoelectric ceramic that does not contain lead or has a low lead content. That is, low volatility, environmental friendliness, and ecological aspects that can minimize the volatilization of lead during firing and the release of lead into the environment after being marketed and discarded as piezoelectric components Therefore, it is possible to use an extremely excellent piezoelectric ceramic.

  Hereinafter, embodiments of the present invention will be described in detail.

  A piezoelectric ceramic according to an embodiment of the present invention includes a first compound having a rhombohedral perovskite structure and a second compound having a tetragonal perovskite structure. And bismuth, at least one divalent metal element selected from the group consisting of magnesium, iron, cobalt, copper and zinc, and at least one tetravalent metal element selected from the group consisting of titanium, zirconium and tin. And a third compound containing oxygen. Alternatively, a solid solution containing the first compound, the second compound, and the third compound is contained. That is, the first compound, the second compound, and the third compound are included, and they may be in solid solution or may not be completely in solution.

  Thereby, in this piezoelectric ceramic, a crystallographic phase boundary (MPB) is formed at least partially, and the piezoelectric characteristics are improved. Specifically, piezoelectric characteristics such as dielectric constant, electromechanical coupling coefficient, and displacement are improved as compared with one-component or two-component systems.

  An example of the first compound is sodium bismuth titanate. The composition of sodium bismuth titanate is represented by, for example, Chemical Formula 1, wherein sodium and bismuth are located at the A site of the perovskite structure and titanium is located at the B site of the perovskite structure.

In the chemical formula 1, s1 represents a composition ratio (hereinafter referred to as A / B ratio) by the molar ratio of the element located at the A site to the element located at the B site, and is 1 if it is a stoichiometric composition. It may deviate from the stoichiometric composition. However, if it is 1 or less, sinterability can be improved and higher piezoelectric characteristics can be obtained, and it is preferable, and if it is in the range of 0.9 or more and 1.0 or less, higher piezoelectric characteristics can be obtained. It is more preferable because it is possible. The composition of sodium and bismuth and the composition of oxygen are determined from the stoichiometric composition and may deviate from the stoichiometric composition.

  The first compound may be composed of one type of compound, but may be composed of a plurality of types of compounds. When consisting of a plurality of types of compounds, they may be in solid solution or not in solution. In the case of a plurality of compounds, the A / B ratio of each compound may be 1 or 1 in the stoichiometric composition, but in each compound, it is 1 or less, and further 0.9 or more and 1.0. It is preferable that it is within the following range, or 1 or less, more preferably 0.9 or more and 1.0 or less in total of each compound.

  An example of the second compound is potassium bismuth titanate. The composition of potassium bismuth titanate is represented by, for example, Chemical Formula 2, wherein potassium and bismuth are located at the A site of the perovskite structure and titanium is located at the B site of the perovskite structure.

In Chemical Formula 2, t1 represents an A / B ratio and is 1 if it is a stoichiometric composition, but may deviate from the stoichiometric composition. However, if it is 1 or less, sinterability can be improved and higher piezoelectric characteristics can be obtained, and it is preferable, and if it is in the range of 0.9 or more and 1.0 or less, higher piezoelectric characteristics can be obtained. It is more preferable because it is possible. The composition of potassium and bismuth and the composition of oxygen are determined from the stoichiometric composition and may deviate from the stoichiometric composition.

  The second compound may be composed of one kind of compound as well as the first compound, but may be composed of a plurality of kinds of compounds. When consisting of a plurality of types of compounds, they may be in solid solution or not in solution. In the case of a plurality of compounds, the A / B ratio of each compound may be 1 or 1 in the stoichiometric composition, but in each compound, it is 1 or less, and further 0.9 or more and 1.0. It is preferable that it is within the following range, or 1 or less, more preferably 0.9 or more and 1.0 or less in total of each compound.

  The third compound exists, for example, in the form of a solid solution in the first compound, the second compound, or both, and the composition is represented by, for example, Chemical Formula 3.

In Chemical Formula 3, M1 represents at least one divalent metal element selected from the group consisting of magnesium, iron, cobalt, copper and zinc, and M2 represents at least one type of four elements selected from the group consisting of titanium, zirconium and tin. Represents a valent metal element. u is 1 if it is a stoichiometric composition, but may deviate from the stoichiometric composition. The composition of the divalent metal element M1 and the tetravalent metal element M2 and the composition of oxygen are determined from the stoichiometric composition and may deviate from the stoichiometric composition.

  The composition ratio of the first compound, the second compound, and the third compound is preferably a molar ratio within the range shown in Chemical Formula 4. Outside this range, the piezoelectric properties are increased away from the crystallographic phase boundary (MPB) between the first compound having a rhombohedral perovskite structure and the second compound having a tetragonal perovskite structure. It is because it will fall. Moreover, even if the content of the third compound is excessive, the piezoelectric characteristics are deteriorated. The composition ratio referred to here is a value in the entire piezoelectric ceramic including those in solid solution and those not in solid solution.

In Formula 4, X is the first compound, Y is the second compound, Z is the third compound, x is the molar ratio of the first compound, y is the molar ratio of the second compound, and z is the third compound. Each represents a molar ratio of the compounds, and x, y, and z are in a range satisfying x + y + z = 1, 0.35 ≦ x ≦ 0.99, 0 <y ≦ 0.55, 0 <z ≦ 0.1, respectively. Value.

  In Formula 4, a more preferable value of x is 0.7 ≦ x ≦ 0.99, and a more preferable value of y is 0 <y ≦ 0.49, and further 0 <y ≦ 0.29. A more preferable value of z is 0.01 ≦ z ≦ 0.1, and further 0.01 ≦ z ≦ 0.05.

  Moreover, it is preferable that the composition ratio of the first compound and the second compound and the A / B ratio of these compounds have the relationship shown in Formula 1. This is because high sinterability and excellent piezoelectric characteristics can be obtained within this range as described in Chemical Formula 1 and Chemical Formula 2.

In Equation 1, α represents the molar ratio of the first compound, β represents the molar ratio of the second compound, and α + β = 1. Further, s represents the A / B ratio in the first compound, t represents the A / B ratio in the second compound, and when the first compound or the second compound is composed of a plurality of types of compounds, The combined value of the first compound or the second compound.

  In particular, when sodium bismuth titanate is included as the first compound and potassium bismuth titanate is included as the second compound, the relationship between the composition ratio and the A / B ratio of these compounds is shown in Formula 2. Preferably a relationship exists.

In Equation 2, α1 represents the molar ratio of sodium bismuth titanate, β1 represents the molar ratio of potassium bismuth titanate, and α1 + β1 = 1. Further, s1 is an A / B ratio of sodium bismuth titanate, that is, a composition ratio by a total molar ratio of sodium and bismuth to titanium in sodium bismuth titanate, and t1 is an A / B ratio of potassium bismuth titanate, ie titanic acid. The composition ratio by the molar ratio of the sum total of potassium and bismuth with respect to titanium in potassium bismuth is each represented. )

  In addition, although this piezoelectric ceramic may contain lead, it is preferable that the content is 1 mass% or less, and it is more preferable if it does not contain lead at all. It is possible to minimize lead volatilization during firing and lead release into the environment after being marketed and disposed of as piezoelectric components. It is because it is preferable. Moreover, the average particle diameter of the crystal grain of this piezoelectric ceramic is 0.5 micrometer-20 micrometers, for example.

  A piezoelectric ceramic having such a configuration can be manufactured, for example, as follows.

First, as starting materials, bismuth oxide (Bi 2 O 3 ), sodium carbonate (Na 2 CO 3 ), potassium carbonate (K 2 CO 3 ), titanium oxide (TiO 2 ), basic magnesium carbonate (4MgCO 3 .Mg ( OH) 2 .4H 2 O), iron oxide (Fe 2 O 3 ), cobalt oxide (Co 3 O 4 ), copper oxide (CuO), zinc oxide (ZnO), zirconium oxide (ZrO 2 ) and tin oxide (SnO) 2 ) If necessary, prepare a powder such as 1 ) and dry it sufficiently at 100 ° C or higher, and then weigh it according to the target composition. In addition, the starting material may be an oxide that is obtained by firing, such as carbonate or oxalate, instead of an oxide. A thing may be used.

  Next, for example, the weighed starting materials are sufficiently mixed in an organic solvent or water for 5 hours to 20 hours by a ball mill or the like, then sufficiently dried, press-molded, and at 750 ° C. to 900 ° C. for about 1 hour to 3 hours. Calcinate. Subsequently, for example, the calcined product is pulverized in an organic solvent or water for 5 hours to 30 hours by a ball mill or the like, dried again, and granulated by adding a binder solution. After granulation, for example, this granulated powder is press-molded into a block shape.

  After forming the block shape, for example, the compact is heat-treated at 400 ° C. to 800 ° C. for about 2 hours to 4 hours to volatilize the binder, and then subjected to main firing at 950 ° C. to 1300 ° C. for about 2 hours to 4 hours. The rate of temperature increase and the rate of temperature decrease during the main firing are, for example, about 50 ° C./hour to 300 ° C./hour. After the main firing, the obtained sintered body is polished as necessary to provide an electrode. After that, polarization treatment is performed by applying an electric field of 5 MV / m to 10 MV / m in silicon oil at 25 ° C. to 150 ° C. for about 5 minutes to 1 hour. Thereby, the piezoelectric ceramic mentioned above is obtained.

  Thus, according to the present embodiment, in addition to the first compound having a rhombohedral perovskite structure and the second compound having a tetragonal perovskite structure, bismuth, magnesium, iron, cobalt, copper and A third compound containing at least one divalent metal element in the group consisting of zinc, at least one tetravalent metal element in the group consisting of titanium, zirconium and tin, and oxygen. In addition, since a solid solution containing these is contained, piezoelectric characteristics such as dielectric constant, electromechanical coupling coefficient, or displacement can be improved.

  Therefore, it is possible to increase the possibility of using a piezoelectric ceramic that does not contain lead or has a low lead content. That is, low volatility, environmental friendliness, and ecological aspects that can minimize the volatilization of lead during firing and the release of lead into the environment after being marketed and discarded as piezoelectric components Therefore, it is possible to use an extremely excellent piezoelectric ceramic.

  In particular, as shown in Chemical formula 4, the composition ratios x, y, and z of the first compound, the second compound, and the third compound are expressed as molar ratios of x + y + z = 1, 0.35 ≦ x ≦ 0. If the values are within the ranges satisfying 99, 0 <y ≦ 0.55 and 0 <z ≦ 0.1, the piezoelectric characteristics can be further improved. Further, x is in the range of 0.7 ≦ x ≦ 0.99, y is in the range of 0 <y ≦ 0.49, and further 0 <y ≦ 0.29, and z is in the range of 0.01 ≦ z ≦ 0. 1 and further within the range of 0.01 ≦ z ≦ 0.05, the piezoelectric characteristics can be further improved.

  Further, the composition ratios α and β of the first compound and the second compound and the A / B ratios s and t of these compounds have a relationship of α + β = 1, 0.9 ≦ αs + βt ≦ 1.0. Or the composition ratio α1, β1 of sodium bismuth titanate and potassium bismuth titanate and the A / B ratio s1, t1 are α1 + β1 = 1, 0.9 ≦ α1s1 + β1t1 ≦ 1.0 If it has, it can improve a piezoelectric characteristic more.

  Furthermore, specific examples of the present invention will be described.

(Examples 1-1 to 1-24)
First, as starting materials of sodium bismuth titanate as the first compound, potassium bismuth titanate as the second compound, and iron and bismuth titanate as the third compound, bismuth oxide powder, sodium carbonate powder, carbonic acid carbonate Potassium powder, titanium oxide powder, and iron oxide powder were prepared, dried sufficiently at 100 ° C. or higher, and then weighed. The blending ratio of the starting materials was changed in Examples 1-1 to 1-24 so that the composition of the molar ratio shown in Chemical Formula 5 and Table 1 was obtained after firing. In Table 1, NBT represents (Na 0.5 Bi 0.5) 0.99 TiO 3, KBT represents (K 0.5 Bi 0.5) 0.99 TiO 3, BFT represents Bi (Fe 0.5 Ti 0.5) O 3.

  Next, the weighed starting materials were mixed in water by a ball mill for about 16 hours, sufficiently dried, press-molded, and calcined at 850 ° C. for about 2 hours. Subsequently, the calcined product was pulverized in water for about 16 hours with a ball mill, dried again, and granulated by adding a polyvinyl alcohol (PVA) aqueous solution as a binder. After that, this granulated powder is formed into a disk-shaped pellet having a diameter of 17 mm and a thickness of 1.5 mm, and heat-treated at 700 ° C. for 2 hours to volatilize the binder, and at 1100 ° C. to 1300 ° C. for 2 to 4 hours. The main firing was performed. The firing conditions were 200 ° C./hour for both temperature rise and temperature drop. Next, the obtained fired body was polished into a parallel plate shape having a thickness of about 0.4 mm to 0.6 mm, and then a silver paste was baked at 600 ° C. to 700 ° C. to obtain an electrode. After that, polarization treatment was performed by applying an electric field of 10 MV / m for 15 minutes in silicon oil at 50 ° C. to 150 ° C. Thereby, the piezoelectric ceramics of Examples 1-1 to 1-24 were obtained.

  For the obtained piezoelectric ceramics of Examples 1-1 to 1-24, the relative dielectric constant εd, the electromechanical coupling coefficient kr in the spreading direction, and the amount of displacement when a voltage pulse of 3 MV / m was applied were measured. At that time, the relative dielectric constant εd is measured by an LCR meter (HP4284A manufactured by Hewlett-Packard), and the electromechanical coupling coefficient kr is measured by an automatic analyzer using an impedance analyzer (HP4194A manufactured by Hewlett-Packard) and a desktop computer. The resonance antiresonance method was used. The displacement was measured by controlling the eddy current non-contact displacement meter, amplifier, oscillator, multimeter, etc. with a desktop computer and applying a voltage in silicon oil. The results are shown in Table 1 and FIG. FIG. 1 shows the relationship between the composition ratio x of sodium bismuth titanate, which is the first compound, and the amount of displacement, according to the composition ratio z of iron / bismuth titanate, which is the third compound.

  Further, as Comparative Examples 1-1 to 1-15 for this example, except that the compounding ratio of the starting materials was changed so that the composition by the molar ratio shown in Chemical Formula 5 and Table 1 was changed after firing. A piezoelectric ceramic was produced under the same conditions as in this example. For Comparative Examples 1-1 to 1-15 as well, the relative dielectric constant εd, the electromechanical coupling coefficient kr in the spreading direction, and the displacement when a voltage pulse of 3 MV / m was applied were measured in the same manner as in this example. . The results are also shown in Table 1 and FIG.

  Comparative Example 1-1 is only the first compound, Comparative Examples 1-2 to 1-6 are only the first compound and the second compound, Comparative Example 1-7 is only the second compound, Comparative Example 1 −8, 1-10, 1-12, and 1-14 are the first compound and the third compound only, and Comparative Examples 1-9, 1-11, 1-13, and 1-15 are the second compound and the third compound. This is a case where only 3 compounds are included. Of these, Comparative Examples 1-1 and 1-7 are comparative examples for Examples 1-1 to 1-24 as a whole, and Comparative Example 1-2 is a comparative example and comparative examples for Examples 1-2, 1-8, and 1-14. Example 1-3 is a comparative example for Examples 1-3, 1-9, 1-15, 1-20, and Comparative Example 1-4 is for Examples 1-4, 1-10, 1-16, 1-21. Comparative Example, Comparative Example 1-5 is a Comparative Example for Examples 1-5, 1-11, 1-17, 1-22, Comparative Example 1-6 is Examples 1-6, 1-7, 1-12, Comparative Examples 1-13, 1-18, 1-19, 1-23, 1-24, Comparative Examples 1-8, 1-9 are Comparative Examples for Examples 1-1 to 1-7, Comparative Example 1 10 and 1-11 are comparative examples for Examples 1-8 to 1-13, Comparative Examples 1-12 and 1-13 are comparative examples for Examples 1-14 to 1-19, and Comparative Examples 1-14 and 1-13. 1 Are applicable to a comparative example for Example 1-20~1-24.

  As shown in Table 1 and FIG. 1, according to this example, a larger value was obtained for the relative dielectric constant εd, the electromechanical coupling coefficient kr, or the displacement than the comparative example. That is, it contains sodium bismuth titanate as the first compound, potassium bismuth titanate as the second compound, and iron and bismuth titanate as the third compound, or a solid solution thereof. Thus, it was found that the piezoelectric characteristics such as the displacement amount can be improved.

  Further, from the results of Examples 1-1 to 1-24, when the composition ratio x of the first compound, the composition ratio y of the second compound, or the composition ratio z of the third compound is increased, the displacement is all. There was a tendency for the amount to increase, to reach a local maximum, and then to decrease. That is, the composition ratios x, y, and z of the first compound, the second compound, and the third compound are expressed as molar ratios: x + y + z = 1, 0.35 ≦ x ≦ 0.99, 0 <y It has been found that the piezoelectric characteristics can be further improved if each of the ranges satisfies ≦ 0.55, 0 <z ≦ 0.1.

  In particular, the composition ratio x of the first compound is in the range of 0.7 ≦ x ≦ 0.99, or the composition ratio y of the second compound is 0 <y ≦ 0.49, and further 0 <y ≦ 0. If the composition ratio z of the third compound is within the range of 29 ≦ 29 or 0.01 ≦ z ≦ 0.1, and further 0.01 ≦ z ≦ 0.05, the piezoelectric characteristics are further improved. I found out that

(Examples 2-1 to 2-8)
In Examples 2-1 to 2-8, the divalent metal element M1 in the third compound was changed to magnesium, cobalt, copper, or zinc so that the composition of the molar ratio shown in Chemical Formula 6 and Table 2 was obtained after firing. A piezoelectric ceramic was produced in the same manner as in Examples 1-3 and 1-9 except that basic magnesium carbonate powder, cobalt oxide powder, copper oxide powder or zinc oxide powder was used as the raw material. In Table 2, NBT represents (Na 0.5 Bi 0.5) 0.99 TiO 3, KBT represents (K 0.5 Bi 0.5) 0.99 TiO 3, BM1T represents Bi (M1 0.5 Ti 0.5) O 3. Also in Examples 2-1 to 2-8, when a dielectric constant εd, an electromechanical coupling coefficient kr in the spreading direction, and a voltage pulse of 3 MV / m were applied in the same manner as in Examples 1-2 and 1-7. The amount of displacement was measured. The results are shown in Table 2 together with the results of Examples 1-3 and 1-9 and Comparative Example 1-3.

  As shown in Table 2, according to Examples 2-1 to 2-8, similarly to Examples 1-3 and 1-9, compared to Comparative Example 1-3, the electromechanical coupling coefficient kr and the displacement amount A large value was obtained for. That is, it can be seen that even if the third compound contains magnesium / bismuth titanate, cobalt / bismuth titanate, copper / bismuth titanate or zinc / bismuth titanate, the piezoelectric characteristics such as displacement can be improved. It was.

(Examples 3-1 to 3-4)
In Examples 3-1 to 3-4, the tetravalent metal element M2 in the third compound is changed to zirconium or tin so that the composition has the molar ratio shown in Chemical Formula 7 and Table 3 after firing, and as a raw material thereof. A piezoelectric ceramic was produced in the same manner as in Examples 1-3 and 1-9 except that zirconium oxide powder or tin oxide powder was used. In Table 3, NBT represents (Na 0.5 Bi 0.5) 0.99 TiO 3, KBT represents (K 0.5 Bi 0.5) 0.99 TiO 3, BFM2 represents Bi (Fe 0.5 M2 0.5) O 3. Also in Examples 3-1 to 3-4, in the same manner as in Examples 1-2 and 1-7, when a dielectric constant εd, an electromechanical coupling coefficient kr in the spreading direction, and a voltage pulse of 3 MV / m were applied. The amount of displacement was measured. The results are shown in Table 3 together with the results of Examples 1-3 and 1-9 and Comparative Example 1-3.

  As shown in Table 3, according to Examples 3-1 to 3-4, as in Examples 1-3 and 1-9, relative dielectric constant εd, electromechanical coupling, as compared with Comparative Example 1-3. Large values were obtained for coefficient kr or displacement. That is, it has been found that even when iron / bismuth zirconate or iron / bismuth stannate is included as the third compound, piezoelectric characteristics such as displacement can be improved.

(Examples 4-1 to 4-5)
In Examples 4-1 to 4-5, the A / B ratio s1 of sodium bismuth titanate, which is the first compound, and the second compound so as to have the composition of the molar ratio shown in Chemical Formula 8 and Table 4 after firing, A piezoelectric ceramic was produced in the same manner as in Example 1-3, except that the A / B ratio t1 of potassium bismuth titanate, which is the compound of Example 1, was changed. In Table 4, NBT represents (Na 0.5 Bi 0.5 ) s1 TiO 3 , KBT represents (K 0.5 Bi 0.5 ) t1 TiO 3 , and BFT represents Bi (Fe 0.5 Ti 0.5 ) O 3 . The values of s1 and t1 are the same in each embodiment. In this example, since the first compound and the second compound are each composed of one kind of compound, the A / B ratio s1 of sodium bismuth titanate remains as it is as the A / B of the first compound. The ratio s means that the A / B ratio t1 of potassium bismuth titanate means the A / B ratio t of the second compound as it is. Therefore, the relationship between the composition ratios α and β of the first compound and the second compound shown in Equation 2 and the A / B ratios s and t of these compounds is the same as s1 and t1.

  For Examples 4-1 to 4-5, as in Example 1-3, the relative dielectric constant εd, the electromechanical coupling coefficient kr in the spreading direction, and the amount of displacement when a voltage pulse of 3 MV / m was applied were measured. did. The results are shown in Table 4 together with the results of Example 1-3.

  As shown in Table 4, as the values of A / B ratios s1 and t1 were decreased, the displacement amount was increased, and a tendency to decrease after showing the maximum value was observed. In particular, it has been found that if the values of the A / B ratios s1 and t1 are in the range of 1.00 or less and 0.90 or more, a good amount of displacement can be obtained. This is probably because when the values of the A / B ratio s1, t1 exceed 1.0, the sinterability deteriorates, the density does not improve, and a high voltage cannot be applied during polarization. Further, when the values of the A / B ratios s1 and t1 are smaller than 0.9, it is considered that a large amount of titanium as the B site component is generated and a heterogeneous phase is generated, and the piezoelectric characteristics are deteriorated. . That is, the composition ratio α, β of the first compound and the second compound and the A / B ratio s, t of these compounds have a relationship of α + β = 1, 0.9 ≦ αs + βt ≦ 1.0. By doing so, it was found that the piezoelectric characteristics such as the displacement amount can be further improved.

  In the above examples, the compositions of the first compound, the second compound, and the third compound have been described with specific examples. However, as described in the above embodiment, other compositions can be used. Even if it is configured to have a composition, similar results can be obtained.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiment and examples, only the case where the first compound, the second compound, and the third compound are included has been described. However, in addition to these, other compounds may be included.

  Moreover, this invention may contain elements other than the element which comprises a 1st compound, a 2nd compound, and a 3rd compound as an impurity or a constituent element of another compound. Examples of such elements include barium (Ba), strontium (Sr), calcium (Ca), lithium (Li), hafnium (Hf), nickel (Ni), tantalum (Ta), silicon (Si), and boron. (B), aluminum (Al), and rare earth elements are mentioned. In particular, hafnium is often contained as an impurity that is difficult to separate from zirconium.

  Furthermore, in the above embodiment, the crystal structures of sodium bismuth titanate and potassium bismuth titanate have been described. However, if the oxide has the above-described composition, or contains a solid solution containing these. Needless to say, these crystal structures are included in the present invention.

  It can be widely used in fields such as actuators, sensors, and resonators.

It is a characteristic view showing the relationship between the composition ratio x of a 1st compound and the displacement according to the composition ratio z of a 3rd compound.

Claims (5)

  1. A first compound comprising sodium bismuth titanate having a rhombohedral perovskite structure;
    A second compound comprising potassium bismuth titanate having a tetragonal perovskite structure;
    Bismuth (Bi), at least one divalent metal element selected from the group consisting of magnesium (Mg), iron (Fe), cobalt (Co), copper (Cu) and zinc (Zn), and titanium (Ti) And a third compound containing at least one tetravalent metal element selected from the group consisting of zirconium (Zr) and tin (Sn), and oxygen (O).
  2. A first compound comprising sodium bismuth titanate having a rhombohedral perovskite structure;
    A second compound comprising potassium bismuth titanate having a tetragonal perovskite structure;
    Bismuth (Bi), at least one divalent metal element selected from the group consisting of magnesium (Mg), iron (Fe), cobalt (Co), copper (Cu) and zinc (Zn), and titanium (Ti) And a solid solution containing at least one tetravalent metal element selected from the group consisting of zirconium (Zr) and tin (Sn), and a third compound containing oxygen (O). porcelain.
  3. The content of lead (Pb) is 1% by mass or less. The piezoelectric ceramic according to claim 1 or 2 , wherein:
  4. The composition ratio of the first compound, the second compound, and the third compound is a molar ratio within the range shown in Chemical Formula 1 to Claim 3. The piezoelectric ceramic according to any one of the above.
    (In Formula 1, X is the first compound, Y is the second compound, Z is the third compound, x is the molar ratio of the first compound, y is the molar ratio of the second compound, and z is the third compound. X, y and z are in the ranges satisfying x + y + z = 1, 0.35 ≦ x ≦ 0.99, 0 <y ≦ 0.55, 0 <z ≦ 0.1, respectively. The value of
  5. Composition ratio of sodium bismuth titanate and potassium bismuth titanate, composition ratio of sodium (Na) and bismuth to titanium (Ti) in sodium bismuth titanate, and potassium (K) to titanium in potassium bismuth titanate and the composition ratio of bismuth, the piezoelectric ceramic according to any one of claims 1 to 4, characterized in that it has a relation shown in Equation 1.
    (In Equation 1 , α1 represents the molar ratio of sodium bismuth titanate, β1 represents the molar ratio of potassium bismuth titanate, and α1 + β1 = 1. Further, s1 represents the ratio of sodium and bismuth to titanium in sodium bismuth titanate. (The composition ratio by the total molar ratio, t1 represents the composition ratio by the total molar ratio of potassium and bismuth to titanium in potassium bismuth titanate, respectively.)
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