JP2011009755A - Piezoelectric member for actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric member for an actuator, having high piezoelectric properties such as a piezoelectric constant, hardly causing cracking or chipping even if grinding work is executed thereto, and allowing an electrode and an electrode extraction line to be formed on a surface thereof even in an unpolished state.SOLUTION: The piezoelectric member for an actuator is formed with a lead zirconate titanate-based sintered body in which: the density of the sintered body is ≥98% of theoretical density; a maximum crystal particle diameter is ≤10 μm; a maximum void diameter is ≤10 μm; surface roughness on a surface of the sintered body in an unpolished state is ≤0.3 μm in center line average roughness (Ra); a void fraction in the sintered body is ≤1.0% when an area at the depth up to 100 μm from the sintered body surface and areas other than it are assumed to be a sintered body surface layer part and a sintered body inside, respectively; and the difference between the void fraction of the sintered body surface layer part and that of the inside of sintered body is ≤1.0%.

Description

  The present invention relates to a piezoelectric member for an actuator made of a lead zirconate titanate-based sintered body used for an ultrasonic motor, an ink jet printer head or the like.

  Conventionally, piezoelectric actuators are used in ultrasonic motors and inkjet printer heads. The basic principle of this piezoelectric actuator is that when an electrode is formed on the opposing surface of a piezoelectric member made of polarized piezoelectric ceramics and a voltage is applied, the crystals in the piezoelectric ceramic are distorted and deformed. As a piezoelectric member for such an actuator, a lead zirconate titanate-based sintered body has been used.

  In order to produce a lead zirconate titanate-based sintered body, a lead zirconate titanate-based synthetic powder synthesized by a chemical method such as an alkoxide method, an oxalic acid method, a hydrothermal synthesis method or a calcining synthesis method, It was manufactured by molding using a known press molding method, tape molding method, or the like, and firing in an air atmosphere (oxygen concentration of about 20% by volume).

  However, it is known that when a lead-based composite material containing PbO as a main component is fired in an air atmosphere, PbO evaporates and various piezoelectric characteristics deteriorate.

  Therefore, as a method for obtaining a lead zirconate titanate-based sintered body without deteriorating various piezoelectric properties by atmospheric firing, JP-A-11-12031 (hereinafter referred to as Patent Document 1) discloses zirconate titanate. It is disclosed that when obtaining a lead-based synthetic powder, PbO that evaporates during firing is excessively added in advance to prevent deterioration of various piezoelectric characteristics.

  In addition, when using a lead zirconate titanate-based sintered body as a piezoelectric member for an actuator, not only high piezoelectric characteristics such as piezoelectric constants but also high fineness and high precision workability are required. There has been a demand for a piezoelectric member for an actuator excellent in mechanical characteristics that does not cause chipping or chipping in microfabrication using a wire saw or the like. In order to prevent the occurrence of chipping and chipping due to microfabrication with a dicing saw, wire saw, etc., the mechanical strength of the lead zirconate titanate-based sintered body itself is improved and voids existing inside the sintered body are also included. It was necessary to reduce the diameter and void ratio.

  Therefore, as a method of obtaining a densified lead zirconate titanate-based sintered body, the void is crushed by the hot isostatic pressing method (HIP method), or Japanese Patent No. 2652425 (hereinafter referred to as Patent Document 2). ), It is proposed that the oxygen concentration at the time of temperature rise is 50% by volume or more, and the oxygen concentration at the firing temperature is ½ to 10% by volume of the temperature rise. It was.

JP-A-11-12031 Japanese Patent No. 2652425

However, as disclosed in Patent Document 1, even if excess PbO is added in advance when weighing the lead zirconate titanate-based synthetic powder, PbO is not suitable for firing in an air atmosphere.
Since it is difficult to prevent the evaporation of PbO and the PbO evaporates from the surface of the sintered body, there is a large difference in composition between the surface layer of the sintered body and the inside of the sintered body, and the difference in void diameter and void ratio. A lead-based sintered body could not be obtained.

  Therefore, when the obtained lead zirconate titanate-based sintered body is used as a piezoelectric member for an actuator, it is necessary to remove the surface layer of the sintered body by grinding, which is wasteful of expensive raw materials and grinding. There was an inconvenience such as long time.

  In addition, even if the surface layer of the sintered body is removed by grinding, the inside of the sintered body is not sufficiently densified, so processing with a dicing saw or wire saw is necessary to grind it to the specified shape. If applied, chipping or chipping is likely to occur, and for example, when an electrode or a fine electrode lead wire is formed, it is a factor that causes disconnection.

  In addition, when firing in an air atmosphere, the amount of PbO evaporation is likely to change with changes in atmospheric pressure, so the composition of the lead zirconate titanate-based sintered body is likely to vary, and stable piezoelectric properties can be obtained. It was difficult to obtain a piezoelectric member for actuator.

  On the other hand, when densified by the hot isostatic pressing method (HIP method), an overall dense lead zirconate titanate-based sintered body can be obtained, but the surface layer of the sintered body and the inside of the sintered body Therefore, it was difficult to obtain a lead zirconate titanate-based sintered body having a homogeneous structure inside and outside the sintered body.

  Therefore, when a sintered body densified by a hot isostatic pressing method (HIP method) is also used as a piezoelectric member for an actuator, the surface layer portion of the sintered body has to be removed by grinding.

  Moreover, since the hot isostatic pressing method (HIP method) is a method of firing while applying external pressure, residual stress remains in the sintered body, and the stress is released during grinding with a dicing saw or wire saw, There was a risk of chipping and chipping.

  In addition, the hot isostatic pressing method (HIP method) is expensive because it requires expensive pressurizing equipment, and the piezoelectric member for the actuator becomes expensive and is not suitable for mass production. There were also challenges.

  On the other hand, in the method disclosed in Patent Document 2, since the change in the furnace atmosphere during firing can be reduced and the evaporation of PbO can be controlled, the lead zirconate titanate-based sintered body is formed as a whole. Even in this method, large voids may remain in the sintered body.

  The reason for this is that when the gradient between the oxygen concentration in the vacancies formed between the lead zirconate titanate-based particles and the oxygen concentration in the outside air increases, the oxygen diffuses, so that the lead zirconate titanate-based particles While filling voids and expelling voids, it tends to promote grain growth, promote sintering, and reduce void diameter.Voids of a certain size disappear, and the void ratio can be reduced. This is probably because voids isolated at the particle interface are taken into the lead zirconate titanate particles as they grow. And it was more difficult to remove voids taken into the lead zirconate titanate particles than to remove voids isolated at the particle interface.

Therefore, grinding a lead zirconate titanate-based sintered body with large voids may cause chipping or chipping, and may cause disconnection when forming electrodes or fine electrode lead wires. It was.

  Therefore, in view of the above problems, the present invention provides a piezoelectric member for an actuator composed of a lead zirconate titanate-based sintered body, wherein the sintered body has a density of 98% or more of the theoretical density, a maximum crystal particle diameter of 10 μm or less, and a maximum. The void diameter is 10 μm or less, the surface roughness on the surface of the sintered body in an unpolished state is 0.3 μm or less in terms of centerline average roughness (Ra), and the depth from the sintered body surface to 100 μm When the thickness is the surface of the sintered body and the other is the inside of the sintered body, the void ratio inside the sintered body is 1.0% or less and the difference in the void ratio between the surface of the sintered body and the inside of the sintered body Is 1.0% or less.

  According to the present invention, the density of the sintered body is 98% or more of the theoretical density, the maximum crystal particle diameter is 10 μm or less, the maximum void diameter is 10 μm or less, and the surface roughness on the surface of the sintered body in an unpolished state. When the degree of centerline average roughness (Ra) is 0.3 μm or less, the depth from the surface of the sintered body to 100 μm is the surface layer of the sintered body, and the other is the inside of the sintered body. Piezoelectric actuator for actuators comprising a lead zirconate titanate-based sintered body having a void ratio within the body of 1.0% or less and a difference in void ratio between the surface portion of the sintered body and the sintered body being 1.0% or less Because it is a member, it is possible to improve various piezoelectric constants such as piezoelectric constants that are important as actuators, and when used as piezoelectric actuators such as ultrasonic motors and inkjet printer heads, the performance can be improved. With, since it has a homogeneous structure, it is not necessary to remove the sintered surface layer portion, it is possible to eliminate the waste of raw materials. In addition, chipping and chipping hardly occur even if grinding is performed to obtain a desired shape, and the surface of the sintered body in an unpolished state is smooth. Therefore, an electrode or an electrode lead wire is directly attached to the surface of the sintered body. Can be formed.

  The piezoelectric member for an actuator according to the present invention is made of a lead zirconate titanate sintered body, has a dense and homogeneous structure, and has a smooth surface in a non-polished state. .

  Further, in the present invention, the term “dense” means that the density of the sintered body has 98% or more of the theoretical density, and it is possible to further improve the piezoelectric characteristics such as the piezoelectric constant by densification, In addition, in the present invention, the smooth surface of the sintered body in the unpolished state means that the center line average roughness (Ra) is 0.3 μm or less, and disconnection is not performed without grinding or the like. Electrodes and electrode lead wires can be formed directly on the surface of the sintered body without being generated.

  Furthermore, having a homogeneous structure in the present invention means that the maximum crystal particle diameter of the lead zirconate titanate-based particles in the sintered body is 10 μm or less and the maximum void diameter is 10 μm or less, and from the surface of the sintered body. When the depth of up to 100 μm is the sintered body surface layer portion and the other is the inside of the sintered body, the void ratio inside the sintered body is 1.0% or less and the voids in the sintered body surface layer portion and inside the sintered body The difference in rate is 1.0% or less.

  Here, the maximum crystal particle diameter of the lead zirconate titanate-based particles is set to 10 μm or less because when the maximum crystal particle diameter exceeds 10 μm, the surface of the sintered body in the unpolished state is centerline average roughness (Ra ) Cannot be reduced to 0.3 μm or less, and the four-point bending strength of the sintered body is greatly reduced and easily damaged, and chipping and chipping occur when grinding is performed.

Moreover, the reason why the maximum void diameter in the sintered body is set to 10 μm or less is that when the maximum void diameter exceeds 10 μm, chipping or chipping occurs starting from this void when grinding is performed, This is because when the void is present on the surface of the sintered body, it causes disconnection when forming an electrode or a fine electrode lead wire.

  Furthermore, the void ratio inside the sintered body is set to 1.0% or less. If the void ratio exceeds 1.0%, the density of the sintered body cannot be set to 98% or more of the theoretical density. This is because when grinding is performed, the ratio of voids that become the starting point of chipping and chipping increases.

  The difference in the void ratio between the sintered body surface layer portion and the sintered body is set to 1.0% or less. Because the characteristics and grindability at the time of grinding process are large, it is difficult to say that it has a homogeneous structure. To use it as a piezoelectric member for actuators, it is necessary to remove the surface layer of the sintered body by grinding process Because.

  Therefore, if the piezoelectric member for actuators made of the lead zirconate titanate sintered body of the present invention satisfying the above composition and structure is used, it has excellent piezoelectric characteristics, so that an ultrasonic motor, an inkjet printer head, etc. It can be suitably used as a piezoelectric actuator, and even when it is ground to form a predetermined shape, no chipping or chipping occurs. Since there are no voids, it is possible to directly form electrodes and electrode lead lines, eliminate the need for a polishing step, shorten the polishing time, and eliminate waste of expensive raw materials.

By the way, in order to manufacture this piezoelectric member for an actuator, as an example, a compound of each element constituting the lead zirconate titanate-based sintered body is weighed, and a chemical such as alkoxide method, oxalic acid method, hydrothermal synthesis method, etc. And a perovskite composition whose basic composition formula is represented by PbZrTiO ₃ synthesized by a method, calcining synthesis method, etc., and Pb in the basic composition formula is a part of at least one element selected from Ba, Sr, and La A lead zirconate titanate-based synthetic powder that is substituted and in which Zr and Ti are partially substituted with at least one of Nb, Zn, Sb, Ni, and Mg is prepared. Here, as a compound of each element constituting the lead zirconate titanate-based sintered body, BaCO _{3 is used} as a component partially replacing Pb with respect to Pb ₃ O ₄ , ZrO ₂ , and TiO ₂ which are basic components. At least one of Nb ₂ O ₅ , ZnO, Sb ₂ O ₃ , NiO, and MgCO ₃ is added as a component that partially replaces at least one of SrCO ₃ and La ₂ O ₃ with Zr and Ti. .

The lead zirconate titanate-based synthetic powder is averaged to 0.4 to 0.7 μm, the standard deviation of particle size distribution is 0.2 μm or less, and the BET specific surface area is 5 to 13 m ² / g using a rotary mill or the like. Grind until

If the average particle size of the lead zirconate titanate-based synthetic powder exceeds 0.7 μm, the BET specific surface area becomes less than 5 m ² / g, and the ratio of the surface energy to the total energy is small, so there is no effect of lowering the firing temperature. When the grain growth is promoted, the maximum crystal particle diameter of the lead zirconate titanate-based particles in the sintered body exceeds 10 μm, and the void is taken into the lead zirconate titanate-based particles by the grain growth and the maximum void diameter is 10 μm. Hereinafter, it is difficult to achieve a void ratio of 1% or less inside the sintered body, and conversely, when the average particle size is less than 0.4 μm, it is difficult to pulverize the BET specific surface area to be 13 m ² / g or less. In addition, the composition is changed due to the mixing of media wear powder. When the standard deviation of the particle size distribution exceeds 0.2 μm, the particle size variation is large, and the lead zirconate titanate particles having a small particle size are incorporated into the lead zirconate titanate particles having a large particle size. It becomes easy to grow grains, it is difficult to make the maximum crystal particle diameter of the lead zirconate titanate-based particles after sintering 10 μm or less, and the maximum void diameter in the sintered body is 10 μm or less due to the incorporation of voids. This is because a void ratio of 1% or less inside the bonded body cannot be achieved.

In addition, when pulverizing the lead zirconate titanate-based synthetic powder, a vibration mill or other pulverization technique may be used in addition to the rotary mill. And in order to adjust the particle size of synthetic powder, media diameters, such as a ball | bowl and a bead, may be selected suitably, and what is necessary is just to grind | pulverize for 10 to 60 hours by wet.

  Next, the obtained lead zirconate titanate-based synthetic powder is mixed with an organic binder and formed into a predetermined shape by a known ceramic forming means such as a press forming method or a tape forming method, and then 200 ° C. to 900 ° C. Then, the organic binder is removed in the air atmosphere, and then placed in a semi-sealed container made of magnesia ceramics or zirconia ceramics together with the powder for adjusting the lead atmosphere.

  Here, the reason for using the semi-sealed container is that oxygen is easily substituted into the container in the atmosphere replacement stage in the firing furnace, and sufficient oxygen is contained in the void formed between the lead zirconate titanate particles. It is because it is necessary to supply. Moreover, the mutual diffusion reaction with the lead zirconate titanate-based sintered body can be prevented by forming the semi-sealed container from magnesia-based ceramics or zirconia-based ceramics. And what is necessary is just to bake at 1000 to 1300 degreeC in the state which made oxygen flow into the baking furnace.

  However, if the oxygen inflow supplied per volume of 1 liter in the firing furnace is less than 0.1 liter / minute, sufficient oxygen is contained in the void formed between the lead zirconate titanate particles in the sintered body. Since the oxygen concentration in the void and the gradient of the oxygen concentration in the outside air are reduced and the oxygen diffusion is suppressed, the effect of expelling the void is small. On the contrary, per volume of 1 liter in the firing furnace If the oxygen inflow rate supplied to the furnace is more than 2.0 liters / minute, the temperature in the furnace may not be stable or the temperature in the furnace may decrease, resulting in firing unevenness. Therefore, the oxygen inflow during firing is 0.1 to 2.0 liters / minute per liter volume in the firing furnace.

  Also, if the oxygen concentration in the furnace atmosphere is less than 25% by volume, the oxygen concentration is too low, so that the evaporation and decomposition of PbO is remarkable, and the oxygen concentration in the void is low. Is difficult to occur and cannot be densified because the void cannot be shrunk. Therefore, in order to increase the shrinkage rate of the voids, the oxygen concentration in the furnace atmosphere should be 25% by volume or more, preferably 50% by volume or more, and more preferably 80% by volume or more.

  As described above, the mean particle size, standard deviation of particle size distribution, and BET specific surface area of the lead zirconate titanate-based synthetic powder are controlled as described above, and oxygen is supplied into the void generated in the firing process. By diffusing, the void can be reduced or eliminated, so the maximum void diameter in the lead zirconate titanate-based sintered body is 10 μm or less, and the void ratio inside the sintered body is 1.0% or less. In addition, the difference in void fraction between the surface portion of the sintered body and the inside of the sintered body can be made 1.0% or less, and the density of the sintered body can be densified to 98% or more of the theoretical density. Further, various piezoelectric characteristics such as a piezoelectric constant that is important as an actuator can be improved, and chipping and chipping do not occur even if grinding is performed to obtain a desired shape. Moreover, since the surface roughness of the surface of the sintered body in an unpolished state can be a smooth surface with a center line average roughness (Ra) of 0.3 μm or less, direct electrodes and electrode lead lines can be formed. Thus, it is possible to form a piezoelectric member for an actuator having effects that the manufacturing process can be reduced and expensive raw material waste can be prevented.

  Hereinafter, an example of the piezoelectric member for actuator according to the present invention will be described.

Pb ₃ O ₄ , SrCO ₃ , ZrO ₂ , TiO ₂ , Nb ₂ O ₅ , ZnO powders were used as starting materials, each powder was weighed in a predetermined amount, wet-mixed in a ball mill for 20 hours, dehydrated and dried. Thereafter, it was calcined at 900 ° C. for 3 hours to obtain lead zirconate titanate-based synthetic powder. Then, the obtained synthetic powder, zirconia balls having a diameter of 0.5 to 10 mm, and ion-exchanged water were put into a container at a ratio of 1: 5: 2, and pulverized with a rotary mill for 20 to 60 hours. As shown in Table 1, the particle size, the standard deviation of the particle size, and the BET specific surface area were varied.

Next, an organic binder is added and kneaded to the obtained synthetic powder, dried and granulated to produce granules, and then the resulting granules are formed by uniaxial pressure molding at a pressure of 1.2 t / cm ^2. After forming the body, the organic binder is removed in an air atmosphere at 300 ° C., and then placed in a semi-enclosed container made of zirconia ceramics, magnesia ceramics, and alumina ceramics together with the powder for adjusting the lead atmosphere, and in the firing furnace Piezoelectric members for actuators comprising the lead zirconate titanate-based sintered bodies of samples A to O shown in Table 2 by adjusting the oxygen inflow amount and oxygen concentration to be supplied as shown in Table 1 and firing at 1100 ° C. Got.

In addition, as a conventional example, using a lead zirconate titanate-based synthetic powder having an average particle diameter, a standard deviation of the particle diameter, and a BET specific surface area shown in Sample P of Table 1, the molded body subjected to the removal treatment was placed in an air atmosphere. The lead zirconate titanate sintered body obtained by firing at 1000 ° C. was placed in a pressure / heating chamber while being put in a semi-sealed container made of magnesia ceramics together with a powder for adjusting the lead atmosphere, and 20 volumes. Piezoelectric actuator for actuator comprising the lead zirconate titanate-based sintered body of sample P shown in Table 2 by filling with argon gas containing% oxygen and sintering at 1100 ° C. under a pressure of 2000 kgf / cm ^2. A member was obtained.

And about the obtained lead zirconate titanate-based sintered body, the relative density of the sintered body, the maximum crystal particle diameter, the maximum void diameter, the surface roughness on the surface of the sintered body in an unpolished state, the inside of the sintered body Investigating void ratio, difference in void ratio between surface layer of sintered body and inside of sintered body, 4-point bending strength and piezoelectric constant (d ₁₅ ) of sintered body, and presence or absence of chipping when grinding It was.

In addition, about the measurement of the maximum void diameter of a sintered compact, the void ratio inside a sintered compact, and the difference of the void ratio inside and outside a sintered compact, a mirror surface process (diamond abrasive grain 0-1 micrometer finish) is given to a sintered compact, Using a LUZEX-FS image analyzer manufactured by Nireco, image analysis was performed under the conditions of a microscope magnification of 200 times, 10 measurement points, and a measurement area of 10.0 × 10 ³ μm ² .

  About the maximum crystal particle size of lead zirconate titanate particles, chemical etching is performed with hydrochloric acid, and the range of 300 μm × 300 μm is measured with a metal microscope in a 200 × field of view. The diameter.

  The surface roughness of the surface of the sintered body in an unpolished state is measured in accordance with JIS B 0601, and in order to confirm the presence or absence of disconnection when an electrode is formed next, a line width of 30 μm is obtained by sputtering. A metal film having a thickness of 0.1 μm was formed, and when this metal film was energized, there was no disconnection, and when it was disconnected, it was evaluated as ×.

The four-point bending strength is based on JIS R1601-1995, and the piezoelectric constant (d ₁₅
) Was performed in accordance with EMAS-6005.

  Furthermore, in order to confirm the presence or absence of chipping or chipping due to grinding, dicing is performed at a pitch of 200 μm using a diamond blade with a thickness of 100 μm to form 300 grooves with a width of 100 μm and a depth of 350 μm. The case where no is seen was evaluated as ○, and the case where chipping or chipping occurred was evaluated as ×. The respective conditions and results are as shown in Tables 1 and 2.

  As a result, although the sample P which is a conventional example is densified, the maximum void diameter exceeds 10 μm, and the difference in the void ratio between the surface portion of the sintered body and the inside of the sintered body exceeds 1%. In order to use it as a piezoelectric member for an actuator, it was necessary to grind the surface layer portion of the sintered body, and chipping and chipping occurred when further grinding was performed.

  In addition, in samples G and L using alumina ceramics as the material of the semi-sealed container at the time of firing, a reaction with the lead zirconate titanate-based sintered body was observed, and this sintered body was used as a piezoelectric member for an actuator. It was necessary to remove the surface layer of the sintered body by grinding.

On the other hand, as shown in Table 1, sample A has an average particle size of lead zirconate titanate-based synthetic powder larger than 0.7 μm, a standard deviation of particles exceeding 0.2, and a BET specific surface area. Since it was less than 5 m ² / g, when it was made into a sintered body, the void ratio inside the sintered body exceeded 1%, and the density of the sintered body was less than 98% of the theoretical density, and the densification was insufficient. Therefore, the piezoelectric constant (d ₁₅ ) was as low as less than 600 pm / V, and chipping and chipping occurred when grinding was performed. In addition, since the difference in void ratio between the sintered body surface layer portion and the inside of the sintered body is larger than 1%, it was necessary to grind the sintered body surface layer portion for use as a piezoelectric member for an actuator. In addition, since the surface of the sintered body in a non-polished state is rough, disconnection occurs when a metal film having a very small width is formed on the surface.

Sample D has a low oxygen concentration at the time of firing. Therefore, when the sintered body is formed, the void ratio inside the sintered body exceeds 1%, and the density of the sintered body is less than 98% of the theoretical density. It was insufficient. Therefore, the piezoelectric constant (d ₁₅ ) was as low as less than 600 pm / V, and chipping and chipping occurred when grinding was performed. In addition, since the difference in void ratio between the sintered body surface layer portion and the inside of the sintered body is larger than 1%, it was necessary to grind the sintered body surface layer portion for use as a piezoelectric member for an actuator.

On the other hand, samples B, C, E, F, H to K, and M to O all have a mean particle size of lead zirconate titanate-based synthetic powder of 0.4 to 0.7 μm and a standard deviation of particles. Is 0.2 or less, the BET specific surface area is in the range of 5 to 13 m ² / g, and the oxygen concentration in the firing furnace is 25 vol% or more using a semi-sealed container of magnesia ceramics or zirconia ceramics at the time of firing. When the sintered body is formed, the void ratio inside the sintered body can be sufficiently densified to be 10% or less, the density of the sintered body can be 98% or more of the theoretical density, and a high piezoelectric constant of 600 pm / V or more. (D ₁₅ ) can be obtained, and since the maximum void diameter in the sintered body can be 10 μm or less, chipping and chipping did not occur even when grinding was performed. In addition, since the maximum crystal particle diameter is 10 μm or less and the surface of the sintered body in the unpolished state can be 0.3 μm or less in the center line average roughness (Ra), a metal is directly applied to the surface of the sintered body in the unpolished state. Even if the film was coated, no disconnection was observed.

Claims (1)

In the piezoelectric member for actuators composed of a lead zirconate titanate-based sintered body, the sintered body has a density of 98% or more of the theoretical density, a maximum crystal particle diameter of 10 μm or less, a maximum void diameter of 10 μm or less, and nothing. The surface roughness on the surface of the sintered body in the polished state is 0.3 μm or less in terms of centerline average roughness (Ra), and the depth from the surface of the sintered body to 100 μm is the surface area of the sintered body, and the others The void ratio in the sintered body is 1.0% or less and the difference in the void ratio in the sintered body surface layer and the sintered body is 1.0% or less. A piezoelectric member for an actuator.