JPH0470267B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to Pb(Y1/2 Nb1/2)O ₃ −PbTiO ₃ −
Consisting of a ternary solid solution whose basic composition is _PbZrO3 ,
The present invention relates to a ceramic piezoelectric material suitable for use in various actuators. [Prior art] Ceramic piezoelectric materials used in actuators have a high pressure constant, a high Curie temperature,
Various properties such as excellent mechanical strength are required. Pb(Y1/2 Nb1/2)O ₃ − is currently the most commonly used ceramic piezoelectric material.
There is a ceramic piezoelectric material made of a ternary solid solution of PbTiO ₃ -PbZrO ₃ . Many studies have been conducted to further improve the above-mentioned properties of this ceramic piezoelectric material. For example, for the purpose of improving mechanical strength, part of Pb in the composition of the solid solution is replaced with Ba, Sr, Ca, etc., and In ₂ O ₃ ,
A material containing 0.1 to 1.0% by weight of MgO, Sb ₂ O ₃ , etc. has been proposed (Japanese Patent Application No. 56-93415 (Japanese Unexamined Patent Publication No. 57-208183)). Improvement in the strength of ceramic piezoelectric materials is particularly required when thin plate-shaped ceramic piezoelectric materials are used as ultrasonic transducers, circuit elements, and the like. however,
When laminating a large number of thin plate-shaped ceramic piezoelectric materials and using them as an actuator, it is important to increase the amount of displacement of the ceramic piezoelectric materials when an electric field is applied, that is, to improve the piezoelectric constant of the piezoelectric material as much as possible, rather than to improve mechanical strength. desired. [Problems to be solved by the invention] The present invention solves Pb(Y1/2 Nb1/2)O ₃ −PbTiO ₃ −
The purpose of this invention is to further improve the piezoelectric constant of the piezoelectric material in a ceramic piezoelectric material made of a three-component solid solution containing PbZrO ₃ as the main component, thereby improving the operation of an actuator using this piezoelectric material. [Means for solving the problems] The ceramic piezoelectric material of the present invention has a basic composition of
Pb(Y1/2 Nb1/2) _O3 0.5-5.0 mol%, _PbTiO3
40.0-50.0 mol%, _PbZrO3 45.0-59.5 mol%
It is a three-component solid solution in which a part of Pb in the above composition is replaced with 5.0 mol % to 15.0 mol % of Sr, and at least one selected from Tb ₄ O ₇ Pr ₆ O ₁₁ NdO is substituted with 0.1 to 2.0 mol %. % by weight. [Effect] The ceramic piezoelectric material having the above composition exhibits a high piezoelectric constant of approximately 400 × 10 ^-12 to approximately 600 × 10 ^{-12 m} /V, and can obtain a large amount of displacement when an electric field is applied. It is effective for use in piezoelectric bodies for various actuators, such as piezoelectric bodies for operating vehicle injectors. [Example] The ceramic piezoelectric material of the present invention is manufactured, for example, by a powder metallurgy method. That is, PbO, TiO ₂ ,
_ZrO2 , _SrCO3 , _Tb4O7 , _{Pr6O11 , NdO} , _{Y2O3 ,}
Raw materials such as Nb ₂ O ₅ are weighed at a predetermined ratio and mixed using a wet ball mill or the like. After drying this mixture, it is calcined at 700 to 900°C for 3 to 10 hours, mixed again in a ball mill, and then dried to obtain a prepared powder. After adding water or an adhesive such as polyvinyl alcohol to the prepared powder and press molding at a pressure of 300 to 1000 kg/cm ² , it is fired at 1200 to 1300°C for 1 to 3 hours to form a cylinder with a diameter of 5 mm and a length of 8 mm. Body. After the surface of the cylindrical body is polished, electrodes are formed on both end faces by a well-known method. This is placed in an insulating oil such as silicone oil at 20 to 100°C, and polarized by applying a DC electric field of 20 to 30 KV/cm between the electrodes for 6 to 60 minutes. Then 1 at 120℃
Aging is performed for a period of time, and the sample is returned to room temperature to obtain a measurement sample. The piezoelectric constant d ₃₃ of the above sample is obtained from the following formula (1),
And K ₃₃ , ε ₃₃ , and S ₃₃ in equation (1) are obtained from the following equations (2), (3), and (4). d ₃₃ = K ₃₃ √ ₃₃・₃₃ ...(1) 1/(K ₃₃ )=0.405fr/fa−fr+0.81 ...(2) ε ₃₃ =C・l/S ...(3) 1/S ₃₃ = 4ρ・fa ²・l ² (1−K ² ₃₃ ) ...(4) Here, l is the length of the sample (m), S is the end surface area of the sample (m ² ), and C is the measured value measured by the LCR meter. 1K measured
Capacitance (F) at Hz, ρ is density (Kg/m ³ ), fa,
fr are anti-resonant and resonant frequencies (Hz), respectively, both of which are measured by well-known methods.
Note that K ₃₃ is an electromechanical coupling coefficient. Regarding the piezoelectric materials of the present invention and comparative materials obtained by the above method with various blending ratios of raw materials,
The piezoelectric constants calculated by measuring the above elements are shown in Tables 1 and 2 in the appendix. In the table, Examples 1 to 10 and Reference Examples 1 to 4
Both contain Tb ₄ O ₇ as an additive. Example 1
-6 and Reference Examples 1 and 2 differ only in the amount of Tb ₄ O ₇ and have the same other compositions. A large piezoelectric constant can be obtained when the amount of Tb ₄ O ₇ added is 0.1 to 2.0 mol %.
Even if the amount of Tb ₄ O ₇ is greater or less than the above range, the piezoelectric constant decreases. Particularly when the amount of Tb ₄ O ₇ is small, sinterability deteriorates and mechanical strength decreases. Examples 8 to 10 and Reference Examples 3 and 4 are all
The amount of Pb replaced by Sr is different. The smaller the amount of substitution, the higher the Curie point, but the smaller the piezoelectric constant. Conversely, as the amount of substitution increases, the Curie point decreases and the piezoelectric constant also decreases. It is known that a suitable substitution amount is 5 to 15 mol%. Examples 7, 11, and 12 and Reference Examples 5 and 6 all differ in the amount of Pb(Y1/2 Nb1/2)O ₃ . Pb(Y1/2
A high piezoelectric constant is exhibited when the amount of Nb1/2) _O3 is 0.5 to 5 mol%. Examples 13 to 17 and Reference Examples 7 to 9 are respectively
The ratio of _PbTiO3 and _PbZrO3 is different. _PbTiO3 40～
50 mol%, _PbZrO3 shows a high piezoelectric constant in the range of 45-58 mol%. Pr ₆ O ₁₁ was used as the additive in Examples 18 and 19, and NdO was used in Examples 20 and 21, respectively.
In addition, in Examples 22 to 24, Tb ₄ O ₇ ,
Two or more of Pr ₆ O ₁₁ and NdO are used in combination. In either case, the same tendency as in the above-mentioned example is shown. Combining the above experimental results, we can conclude that Pb(Y1/2 Nb
1/2) _O3 0.5-5.0 mol%, _PbTiO3 40.0-50.0
Part of the Pb in the solid solution having a basic composition of 45.0 to 58.0 mol % of PbZrO ₃ is replaced with 5.0 to 15.0 mol % of Sr, and Tb ₄ O ₇ Pr ₆ O ₁₁ as an additive,
At least one type of NdO is added in an amount of 0.1 to 2.0 relative to the basic composition.
It is known that a piezoelectric material containing % by weight has excellent mechanical strength, maintains a high Curie temperature, and has particularly excellent piezoelectric constant. The basic composition of Pb(Y1/2 Nb1/2) _O3 is 0.5 mol%
If it is less than 5.0 mol %, the piezoelectric constant will be low, and if it exceeds 5.0 mol %, it will be difficult to obtain a uniform solid solution, and the piezoelectric constant will also decrease. When PbTiO ₃ is out of the range of 40.0 to 50.0 mol %, the dielectric constant becomes low and a high piezoelectric constant cannot be obtained. Pb(Y1/2 Nb1/2)O3 _is 0.5 to 5.0 mol%, _PbTiO3 is 40.0 to 50.0 mol%, and the remainder of the basic composition (45.0 to 59.5 mol%) is composed of _PbZrO3 . If the amount of Pb replaced by Sr in the composition is less than 5.0 mol %, the dielectric constant will be small and a high piezoelectric constant will not be obtained. On the other hand, if the amount is more than 15.0 mol%, the Curie temperature will drop significantly, which is not practical. If the amount of the additive is less than 0.1% by weight, the sinterability will be low and the mechanical strength will be reduced. If it exceeds 2.0% by weight, the Curie point will be low, which is undesirable. Since the piezoelectric material of the present invention has the above-mentioned excellent properties, it can be suitably used for actuators.

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Claims (1)

[Claims] 1 Basic composition: Pb(Y1/2 Nb1/2)O ₃ 0.5 to 5.0 mol%, PbTiO ₃ 40.0 to 50.0 mol%, PbZrO ₃
A solid solution consisting of 45.0 to 59.5 mol%, in which a portion of Pb is replaced by 5.0 mol% to 15.0 mol% of Sr.
A ceramic piezoelectric material characterized in that it contains at least one member selected from Tb ₄ O ₇ Pr ₆ O ₁₁ NdO in a total amount of 0.1 to 2.0% by weight based on the basic composition.