JP2009184904A - (Li, Na, K) (Nb, Ta, Sb) O3 BASED PIEZOELECTRIC MATERIAL AND MANUFACTURING METHOD THEREOF - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide piezoelectric materials having further improved electrical properties, and a manufacturing method thereof. <P>SOLUTION: The (Li, Na, K) (Nb, Ta, Sb) O<SB>3</SB>based piezoelectric material has a sintered compact having a surface microstructure comprises microscopic grains having a grain diameter of less than 5 μm, intermediate grains having a grain diameter of 5 μm or more and less than 15 μm, and coarse grains having a grain diameter of 15 μm or more and less than 50 μm, wherein the amount of coarse grains is 3% or more in a share of grains in terms of area, and thereby the high electrical properties (relative dielectric constant, piezoelectric constant, dielectric loss, and electric-field-induced strain) are obtained. In order to obtain the piezoelectric materials containing microscopic grains, intermediate grains and coarse grains, where the amount of coarse grains is 3% or more, the piezoelectric materials are manufactured by mixing metal-containing compounds so as to give the composition represented by (Li, Na, K) (Nb, Ta, Sb) O<SB>3</SB>, calcining the mixture and then crushing the resultant to obtain a calcined/crushed powder, then keeping temperature constantly at a temperature within the range from 800 to 950°C for a predetermined period of time in a constant temperature keeping process, and raising temperature to firing temperature for sintering. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a (Li, Na, K) (Nb, Ta, Sb) O ₃ based piezoelectric material used for actuators and sensors, and a method for manufacturing the same.

  Piezoelectric / electrostrictive actuators have the advantage that displacement can be precisely controlled on the order of submicrons. In particular, a piezoelectric / electrostrictive actuator using a sintered body of a piezoelectric / electrostrictive porcelain composition as a piezoelectric / electrostrictive body can precisely control displacement, and has high electromechanical conversion efficiency. It has the advantages of high power, fast response speed, high durability, and low power consumption. Taking advantage of these advantages, it is employed in inkjet printer heads, diesel engine injectors, and the like.

As a piezoelectric / electrostrictive ceramic composition for a piezoelectric / electrostrictive actuator, a Pb (Zr, Ti) O ₃ (PZT) -based piezoelectric / electrostrictive ceramic composition has been conventionally used. (Li, Na, K) (Nb, Ta) O ₃ -based piezoelectric / electrostrictive porcelain compositions have been studied since the influence of lead solutes on the global environment is strongly concerned. .

(Li, Na, K) (Nb, Ta) O ₃ piezoelectric materials are generally sintered at 1020 to 1250 ° C. × 0.15 to 4 hours (in the air or in an oxygen atmosphere) (for example, patents). Literatures 1-3). About the temperature increase rate until it reaches the sintering temperature, the temperature is increased at a constant rate from room temperature to the sintering temperature at 200 ° C./h or 300 ° C./h (for example, Patent Document 4).

  And there is a research example of removing the organic binder added to improve the moldability of the powder by keeping it in the range of 600 to 650 ° C. for 1 to 5 hours during the temperature rise (for example, debinding process) (for example, Patent Document 4). The microstructure of these sintered bodies is composed of particles of about 10 μm (for example, Patent Document 1). There is also an example of research aimed at an oriented structure (Patent Document 5).

M.M. Matsubara et. al. , Jpn. J. et al. Appl. Phys. 44 (2005) p. 6136-6142. E. Hollenstein et. al. , Appl. Phys. Lett. 87 (2005) 182905. Y. Guo et. al. , App. Phys. Lett. 85 (2004) 4121 JP 2006-028001 A Y. Saito et. al. , Nature 432, 84-87 (2004)

  Conventionally, in order to improve electrical characteristics, research has been conducted aiming at a uniform microstructure or an oriented structure with a small particle size. However, for example, the electric field induced strain S4000 is insufficient at 400 to 550 ppm, and a piezoelectric material with further improved electrical characteristics such as electric field induced strain is desired.

An object of the present invention is to provide a (Li, Na, K) (Nb, Ta, Sb) O ₃ -based piezoelectric material having further improved electrical characteristics, and a method for manufacturing the same.

The inventors of the present application maintain the surface of the sintered body by maintaining the calcined / ground powder at a constant temperature in the range of 800 to 950 ° C. for a certain period of time and then further heating and sintering at the firing temperature. The microstructure is composed of fine particles having a particle size of less than 5 μm, intermediate particles having a particle size of 5 μm or more and less than 15 μm, and coarse particles having a particle size of 15 μm or more and 50 μm or less. It has been found that an improved (Li, Na, K) (Nb, Ta, Sb) O ₃ based piezoelectric material can be obtained. That is, according to the present invention, the following (Li, Na, K) (Nb, Ta, Sb) O ₃ based piezoelectric material is provided.

[1] The surface microstructure of the sintered body is composed of fine particles having a particle size of less than 5 μm, intermediate particles having a particle size of 5 μm or more and less than 15 μm, and coarse particles having a particle size of 15 μm or more and 50 μm or less. % (Li, Na, K) (Nb, Ta, Sb) O ₃ based piezoelectric material.

[2] The (Li, Na, K) (Nb, Ta, Sb) O ₃ -based piezoelectric material according to [1] containing 30% to 60% of the fine particles on an area basis.

[3] Composition formula: {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃
(However, 1 ≦ a ≦ 1.05, 0.3 ≦ x ≦ 0.7, 0.02 ≦ y ≦ 0.1, 0 ≦ z ≦ 0.5, and 0.01 ≦ w ≦ 0.1. )
The (Li, Na, K) (Nb, Ta, Sb) O ₃ piezoelectric material according to [1] or [2] represented by

[4] (Li, any one of the above [1] to [3] containing at least one metal element selected from the group consisting of Mn, Cr, Fe, Co, Ni, Cu, and Zn Na, K) (Nb, Ta, Sb) O ₃ piezoelectric material.

[5] (Li, Na, K) (Nb, Ta, Sb) O ₃ is mixed with a compound containing a metal element and calcined and calcined and calcined / pulverized powder. In the temperature raising process, after performing a keeping process of maintaining at a constant temperature within a range of 800 to 950 ° C. for a certain time, the temperature is further raised and sintered at a firing temperature (Li, Na, K) ( Nb, Ta, Sb) Manufacturing method of O ₃ based piezoelectric material.

[6] The method for producing a (Li, Na, K) (Nb, Ta, Sb) O ₃ -based piezoelectric material according to [5], wherein a constant time of 0.5 to 20 hours is maintained in the keep step.

[7] The above [5] or [5], wherein at least one metal element selected from the group consisting of Mn, Cr, Fe, Co, Ni, Cu, and Zn is added to the calcined / ground powder, and then fired. 6] The method for producing a (Li, Na, K) (Nb, Ta, Sb) O ₃ -based piezoelectric material according to [6].

It consists of fine particles having a particle size of less than 5 μm, intermediate particles having a particle size of 5 μm or more and less than 15 μm, and coarse particles having a particle size of 15 μm or more and 50 μm or less, and containing 3% or more of coarse particles on an area basis (Li, Na, K) (Nb, By producing a Ta, Sb) O ₃ -based piezoelectric material, a piezoelectric material with improved electrical characteristics such as electric field induced strain can be obtained.

The calcined / ground powder obtained by calcining the raw material represented by (Li, Na, K) (Nb, Ta, Sb) O ₃ is maintained at a constant temperature within a range of 800 ° C. to 950 ° C. for a predetermined time. After performing the keeping step, the piezoelectric material containing the fine grains, intermediate grains, and coarse grains as described above can be obtained by further raising the temperature and sintering at the firing temperature. A piezoelectric material with improved electrical characteristics such as strain can be obtained.

  Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

The (Li, Na, K) (Nb, Ta, Sb) O ₃ piezoelectric material of the present invention has a sintered body whose surface microstructure is fine particles having a particle size of less than 5 μm, intermediate particles having a particle size of 5 μm or more and less than 15 μm. , Consisting of coarse particles having a particle size of 15 μm or more and 50 μm or less, and containing 3% or more of coarse particles on an area basis. Here, the particle diameter is an equivalent area equivalent circle diameter, which is a diameter of a circle having the same area as each particle when the surface of the sintered body is observed with an SEM or the like. Furthermore, it is preferable to make it the structure which contains 30%-60% of a fine grain on an area basis.

The conventional (Li, Na, K) (Nb, Ta, Sb) O ₃ based piezoelectric material has 2% or less of coarse particles having a particle diameter of 15 μm or more and 50 μm or less, and 3% of coarse particles as in the present invention. By setting it as the above, an electrical property can be improved greatly. The production method for making coarse particles 3% or more has not been known in the past, and, as will be described later, after performing a keeping process for a predetermined time in a predetermined temperature range, by further sintering at a higher temperature , What you get. That is, by introducing such a keep process, a (Li, Na, K) (Nb, Ta, Sb) O ₃ piezoelectric material containing 3% or more of coarse particles that could not be produced conventionally is produced. It seems that the ratio of coarse particles is slightly increased compared to the conventional one, but its electrical characteristics are remarkably improved.

The (Li, Na, K) (Nb, Ta, Sb) O ₃ piezoelectric material of the present invention has at least one ion selected from the group consisting of Li, Na, and K at the A site, and Nb, at the B site. It has a perovskite structure including at least one ion selected from the group consisting of Ta and Sb.

More specifically, there can be mentioned those represented by the following composition formula.
{Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃
(However, 1 ≦ a ≦ 1.05, 0.3 ≦ x ≦ 0.7, 0.02 ≦ y ≦ 0.1, 0 ≦ z ≦ 0.5, and 0.01 ≦ w ≦ 0.1. )

  The reason why the A / B ratio is set to a ≦ 1.05 is that if it exceeds this range, the dielectric loss increases and the electric field induced strain when applying a high electric field tends to be small. The increase in dielectric loss is a serious problem in a piezoelectric / electrostrictive ceramic composition for an actuator that applies a high electric field. On the other hand, the reason why 1 ≦ a is set is to promote grain growth and densify. Below this range, heating at 1100 ° C. or higher is required to promote grain growth. In this case, evaporation of the alkali component is likely to occur, and the characteristics become unstable due to fluctuations in the composition.

The reason why the Sb substitution amount is set to 0.01 ≦ w ≦ 0.1 is that the tetragonal-orthorhombic phase transition temperature (hereinafter simply referred to as “phase transition temperature”) in which the piezoelectric / electrostrictive characteristics are enhanced in this range. This is because the electric field induced strain at the time of applying a high electric field can be increased without greatly changing _TOT . In particular, when the Sb substitution amount is 0.01 ≦ w ≦ 0.05, the electric field induced strain when a high electric field is applied can be particularly increased without substantially changing the phase transition temperature _TOT . This is because heterogeneous phases LiSbO ₃ When Sb substitution amount exceeds the range of 0.01 ≦ w ≦ 0.05 is generated in the interior of the sintered body, the phase transition temperature _{T OT} is upward trend.

  The K, Li, and Ta amounts were set to 0.3 ≦ x ≦ 0.7, 0.02 ≦ y ≦ 0.1, and 0 ≦ z ≦ 0.5, respectively. This is because an electrostrictive porcelain composition can be obtained. For example, when x is less than this range, the piezoelectric / electrostrictive characteristics are rapidly lowered. On the other hand, if x exceeds this range, sintering becomes difficult and the firing temperature must be increased. It is not desirable to increase the firing temperature because the alkali component contained in the piezoelectric / electrostrictive porcelain composition evaporates and the piezoelectric / electrostrictive characteristics cannot be obtained stably when the firing temperature is increased. is there. If y is less than this range, sintering is still difficult, and the firing temperature must be increased. On the other hand, when y exceeds this range, precipitation of heterogeneous phases increases, and the insulation properties decrease. Furthermore, if z exceeds this range, it becomes difficult to sinter and the firing temperature must be increased (the composition range of the above composition formula is described in Japanese Patent Application No. 2007-259706). )

The (Li, Na, K) (Nb, Ta, Sb) O ₃ piezoelectric material of the present invention is at least one selected from the group consisting of Mn, Cr, Fe, Co, Ni, Cu, and Zn. It is preferable to contain these metal elements. These elements are transition metal elements or typical metal elements, belonging to Group 6 to Group 12 of the 4th period with similar chemical properties, and are incorporated into the grain boundary phase to lower the melting point of the grain boundary phase. To grow coarse grains. These elements may be contained not only in the grain boundary phase but also in the grains or in different phases as oxides. It is desirable that the metal element as the accessory component is contained so that the amount of addition in terms of metal atom is 3 mol parts or less with respect to 100 mol parts of the perovskite oxide. The reason why the content is 3 mol parts or less is that when the content exceeds this range, the dielectric loss increases, and the electric field induced strain at the time of applying a high electric field tends to be small.

Next, a method for producing the (Li, Na, K) (Nb, Ta, Sb) O ₃ piezoelectric material of the present invention will be described. First, raw material powder is manufactured. The compound containing each metal element is weighed so as to satisfy the ratio (molar ratio) of each metal element in the composition of the raw material powder, and mixed with a solvent such as ethanol by a mixing method such as a ball mill to obtain a mixed slurry. . The type of the compound containing each metal element is not particularly limited, but an oxide or carbonate of each metal element is preferably used. For example, lithium carbonate, potassium tartrate, sodium tartrate, niobium oxide, oxide Tantalum can be used.

  The obtained mixed slurry is dried, calcined, or pulverized by using a drier or by an operation such as filtration. The pulverization may be performed by a method such as a ball mill. In this way, raw material powder (calcined / ground powder) is produced.

  The average particle diameter of the raw powder after calcination and pulverization is preferably 0.1 μm or more and 1 μm or less. Here, the average particle diameter is a 50% diameter (median diameter) in the cumulative distribution.

(Li, Na, K) (Nb, Ta, Sb) O ₃ calcined / ground powder, at least one metal element selected from the group consisting of Mn, Cr, Fe, Co, Ni, Cu, and Zn It is preferable to add. This calcined / ground powder is formed into pellets and fired. Firing is performed at a constant temperature in the range of 800 to 950 ° C. during a temperature rising process, and then maintained at a constant time, and then further heated to sinter at the sintering temperature. Preferably, in the keeping step, it may be maintained for a fixed time of 0.5 to 20 hours. In particular, a range of a keep temperature of 850 to 900 ° C. is more preferable. The firing may be normal firing in the air, firing in an oxygen atmosphere, or hot press firing.

  Thereafter, the obtained sintered body is processed into an appropriate shape (for example, a square plate shape) as necessary, and then subjected to polarization treatment to be used as a piezoelectric material. The polarization treatment is performed by applying a voltage of about 5 kV / mm to the piezoelectric material for 15 minutes or more.

As described above, a sintered body containing fine particles having a particle size of less than 5 μm, intermediate particles having a particle size of 5 μm or more and less than 15 μm, and coarse particles having a particle size of 15 μm or more and 50 μm or less and containing 3% or more of coarse particles on an area basis is prepared. By doing so, electrical characteristics (electric field induced strain, relative dielectric constant, piezoelectric constant, dielectric loss, etc.) can be improved. Further, an auxiliary agent such as MnO ₂ may be added to the calcined / ground powder for forming the (Li, Na, K) (Nb, Ta, Sb) O ₃ piezoelectric material. Moreover, it is good to put in the baking schedule the keep process which keeps at fixed temperature in the middle of the temperature rising process from room temperature to sintering temperature. As a result, a sintered body having the above-described microstructure is obtained, and the electrical characteristics are improved. The electrical characteristics are improved because internal stress is applied to the sintered body.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

(Comparative Example 1)
{Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃ (x = 0.450, y = 0.060, z = 0.082, a = 1.01, w = 0.040) +0.02 mol% MnO ₂ calcined / ground powder (particle size 0.2-0.5 μm, spherical shape) was formed into pellets (pellet) Sample). This pellet-like sample was heated to a firing temperature of 1000 ° C. at a rate of 200 ° C./h in the atmosphere. After holding at 1000 ° C. for 3 hours, the furnace was cooled. The X-ray diffraction profile on the surface of the sintered body was measured, and c / a (tetragonality) of the ratio of c axis to a axis was calculated by the half-width half-point method. The microstructure of the sintered body surface was observed with a scanning electron microscope (SEM). The bulk density by the Archimedes method was measured. From the surface microstructure of the obtained sintered body (see the SEM photograph in FIG. 2), the particle size distribution by the equivalent area equivalent circle diameter (diameter) was analyzed with the vertical axis as the area standard. After processing into a strip shape, 5 kV / mm × 15 min. In silicon oil. Electrical properties (relative permittivity ε, piezoelectric constant d ₃₁ , dielectric loss tan δ, electric field induced strain S4000, temperature T _OT at which the dielectric constant at the time of temperature rise becomes maximum, etc.) Evaluated. S4000 is the amount of strain in 31 directions (perpendicular to the direction of electric field application) when an electric field of 4 kV / mm is applied. These results are shown in Tables 1 and 2.

(Example 1)
The pellet-like sample shown in Comparative Example 1 was heated to 800 ° C. at a rate of 200 ° C./h in the atmosphere, held at 800 ° C. for 3 hours, and then increased to a firing temperature of 1000 ° C. at a rate of 200 ° C./h. Warm up. After holding at 1000 ° C. for 3 hours, the furnace was cooled. The characteristics and crystal structure / microstructure described in Comparative Example 1 were evaluated. These results are shown in Table 1.

(Example 2)
The pellet-like sample shown in Comparative Example 1 was heated to 850 ° C. at a rate of 200 ° C./h in the atmosphere, held at 850 ° C. for 3 hours, and then increased to a firing temperature of 1000 ° C. at a rate of 200 ° C./h. Warm up. After holding at 1000 ° C. for 3 hours, the furnace was cooled. The characteristics and crystal structure / microstructure described in Comparative Example 1 were evaluated. These results are shown in Table 1.

(Example 3)
The pellet-like sample shown in Comparative Example 1 was heated to 880 ° C. at a rate of 200 ° C./h in the atmosphere, held at 880 ° C. for 3 hours, and then increased to a firing temperature of 1000 ° C. at a rate of 200 ° C./h. Warm up. After holding at 1000 ° C. for 3 hours, the furnace was cooled. The characteristics and crystal structure / microstructure described in Comparative Example 1 were evaluated. These results are shown in Tables 1, 2 and 3. FIG. 1 shows the surface microstructure of the sintered body.

Example 4
The pellet-like sample shown in Comparative Example 1 was heated to 900 ° C. at a rate of 200 ° C./h in the atmosphere, held at 900 ° C. for 3 hours, and then increased to a firing temperature of 1000 ° C. at a rate of 200 ° C./h. Warm up. After holding at 1000 ° C. for 3 hours, the furnace was cooled. The characteristics and crystal structure / microstructure described in Comparative Example 1 were evaluated. These results are shown in Table 1.

(Example 5)
The pellet-like sample shown in Comparative Example 1 was heated to 950 ° C. at a rate of 200 ° C./h in the atmosphere, held at 950 ° C. for 3 hours, and then increased to a firing temperature of 1000 ° C. at a rate of 200 ° C./h. Warm up. After holding at 1000 ° C. for 3 hours, the furnace was cooled. The characteristics and crystal structure / microstructure described in Comparative Example 1 were evaluated. These results are shown in Table 1.

(Comparative Example 2)
The pellet-like sample shown in Comparative Example 1 was heated to 960 ° C. at a rate of 200 ° C./h in the atmosphere, held at 960 ° C. for 3 hours, and then increased to a firing temperature of 1000 ° C. at a rate of 200 ° C./h. Warm up. After holding at 1000 ° C. for 3 hours, the furnace was cooled. The characteristics and crystal structure / microstructure described in Comparative Example 1 were evaluated. These results are shown in Table 1.

(Example 6)
The pellet-like sample shown in Comparative Example 1 was heated to 880 ° C. at a rate of 200 ° C./h in the atmosphere, held at 880 ° C. for 0.5 hour, and then fired at 1000 ° C. at a rate of 200 ° C./h. The temperature was raised to. After holding at 1000 ° C. for 3 hours, the furnace was cooled. The characteristics and crystal structure / microstructure described in Comparative Example 1 were evaluated. These results are shown in Table 2.

(Example 7)
The pellet-like sample shown in Comparative Example 1 was heated to 880 ° C. at a rate of 200 ° C./h in the atmosphere, held at 880 ° C. for 6 hours, and then increased to a firing temperature of 1000 ° C. at a rate of 200 ° C./h. Warm up. After holding at 1000 ° C. for 3 hours, the furnace was cooled. The characteristics and crystal structure / microstructure described in Comparative Example 1 were evaluated. These results are shown in Table 2.

(Example 8)
The pellet-like sample shown in Comparative Example 1 was heated to 880 ° C. at a rate of 200 ° C./h in the atmosphere, held at 880 ° C. for 13 hours, and then increased to a firing temperature of 1000 ° C. at a rate of 200 ° C./h. Warm up. After holding at 1000 ° C. for 3 hours, the furnace was cooled. The characteristics and crystal structure / microstructure described in Comparative Example 1 were evaluated. These results are shown in Table 2.

Example 9
The pellet-like sample shown in Comparative Example 1 was heated to 880 ° C. at a rate of 200 ° C./h in the atmosphere, held at 880 ° C. for 20 hours, and then increased to a firing temperature of 1000 ° C. at a rate of 200 ° C./h. Warm up. After holding at 1000 ° C. for 3 hours, the furnace was cooled. The characteristics and crystal structure / microstructure described in Comparative Example 1 were evaluated. These results are shown in Table 2.

(Example 10)
After processing the sintered compact produced by the procedure of Example 3 into a strip shape, polarization treatment was performed in silicon oil under the conditions of 5 kV / mm × 15 min (80 ° C.) to evaluate the electrical characteristics. These results are shown in Table 3.

  Table 1 shows the keep temperature dependence, and the keep time is 3 hours. The characteristics are room temperature data, and the relative dielectric constant and piezoelectric constant are values after polarization. The fine particles have a particle size of less than 5 μm, the intermediate particles have a particle size of 5 to 15 μm, and the coarse particles have a particle size of 15 to 50 μm. The proportion of grains was calculated on an area basis.

  Table 2 shows the keep time dependency, and the keep temperature is 880 ° C. Similarly to Table 1, the characteristics are room temperature data, and the relative dielectric constant and piezoelectric constant are values after polarization. The fine particles have a particle size of less than 5 μm, the intermediate particles have a particle size of 5 to 15 μm, and the coarse particles have a particle size of 15 to 50 μm. The proportion of grains was calculated on an area basis.

  Table 3 shows the polarization temperature dependency, and the keeping condition is 880 ° C. × 3 h. The characteristics are room temperature data, and the relative dielectric constant and piezoelectric constant are values after polarization.

  From the above results, by placing a constant temperature keeping process in the firing schedule between 800 to 950 ° C. (850 to 900 ° C. is better) by keeping a constant temperature during the temperature rising process from room temperature to the firing temperature, The proportion of fine particles having a diameter of less than 5 μm decreased, the proportion of coarse particles having a particle size of 15 μm or more and 50 μm or less increased, and electrical characteristics including electric field induced strain S4000 were improved. The keep time was 0.5 hours or more and the effect of improving the characteristics was exhibited, and the characteristics tended to slightly decrease after 20 hours. Under the keeping conditions with improved electrical characteristics, the proportion of fine grains decreased, the proportion of coarse grains increased, and c / a (tetragonal) increased. However, when the sintered body is pulverized and the X-ray diffraction profile is measured, the c / a of the pulverized powder is reduced regardless of the original microstructure of the sintered body, and is equal to all samples. It was. Therefore, internal stresses exist in the sintered bodies seen in Examples 1 to 9, whereby a tetragonal crystal becomes nearly stable in a room temperature region, c / a is large, and electric field induced strain is included. It has improved electrical characteristics.

  The mechanism by which fine grains are reduced and coarse grains are increased by the keeping process is as follows. The keeping step in the range of 800 to 950 ° C. spreads the grain boundary phase thinly and uniformly. Thereby, grain growth is suppressed, that is, energy for grain growth is stored. When a metal element such as Mn is taken into the grain boundary phase, the melting point of the grain boundary phase is lowered and dissolved at the firing temperature. At that time, since the stored grain growth energy is released at once, coarse grains grow. Since the particles on the spatially discontinuous surface and pores are difficult to be taken into the coarse particles, they become fine particles and intermediate particles.

The microstructure of the sintered body is composed of fine particles having a particle size of less than 5 μm, intermediate particles having a particle size of 5 μm or more and less than 15 μm, and coarse particles having a particle size of 15 μm or more and 50 μm or less, and containing 3% or more of coarse particles on an area basis Therefore, high electrical characteristics (relative dielectric constant, piezoelectric constant, dielectric loss, electric field induced strain) can be obtained. This is due to the effect of internal stress. As means for obtaining such a microstructure, (1) calcined / ground powder having a composition of (Li, Na, K) (Nb, Ta, Sb) O ₃ is added to Mn, Cr, Fe, Co, Ni, Cu It is effective to add an auxiliary mainly containing Zn, and (2) to add a step of keeping at 800 to 950 ° C. in the firing step. By this method, S4000, which was 537 ppm, could be improved up to 621 ppm. Furthermore, it was able to be improved to 670 ppm by performing high temperature polarization treatment. In addition, although the said Example was baked in air | atmosphere, it confirmed that the same effect was acquired even if it baked in oxygen atmosphere and hot press baking.

  The piezoelectric material of the present invention exhibits excellent electric field induced strain, and is suitable for an actuator, a sensor, etc. as a piezoelectric element.

4 is a SEM photograph showing the surface microstructure of Example 3. 4 is a SEM photograph showing a surface microstructure of Comparative Example 1.

Claims (7)

The surface microstructure of the sintered body is composed of fine particles having a particle size of less than 5 μm, intermediate particles having a particle size of 5 μm or more and less than 15 μm, and coarse particles having a particle size of 15 μm or more and 50 μm or less, and containing 3% or more of the coarse particles on an area basis. (Li, Na, K) (Nb, Ta, Sb) O ₃ piezoelectric material. The (Li, Na, K) (Nb, Ta, Sb) O ₃ based piezoelectric material according to claim 1, comprising 30% to 60% of the fine particles on an area basis. Composition formula: {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃
(However, 1 ≦ a ≦ 1.05, 0.3 ≦ x ≦ 0.7, 0.02 ≦ y ≦ 0.1, 0 ≦ z ≦ 0.5, and 0.01 ≦ w ≦ 0.1. )
The (Li, Na, K) (Nb, Ta, Sb) O ₃ piezoelectric material according to claim 1 or 2 represented by: The (Li, Na, K) according to any one of claims 1 to 3, comprising at least one metal element selected from the group consisting of Mn, Cr, Fe, Co, Ni, Cu, and Zn. (Nb, Ta, Sb) O ₃ based piezoelectric material. (Li, Na, K) (Nb, Ta, Sb) A compound containing a metal element was mixed and calcined so as to have a composition represented by O ₃ , and then pulverized to obtain a calcined / ground powder. In the temperature raising process, after performing a keeping step of maintaining at a constant temperature in the range of 800 to 950 ° C. for a certain time, the temperature is further raised and sintered at the firing temperature (Li, Na, K) (Nb, Ta , Sb) Manufacturing method of O ₃ based piezoelectric material. The method for producing a (Li, Na, K) (Nb, Ta, Sb) O ₃ -based piezoelectric material according to claim 5, wherein the keeping step is maintained for a fixed time of 0.5 to 20 hours. The calcined / pulverized powder is fired after adding at least one metal element selected from the group consisting of Mn, Cr, Fe, Co, Ni, Cu, and Zn. Li, Na, K) (Nb, Ta, Sb) O ₃ based piezoelectric material manufacturing method.