JPH0582340B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrostrictive element material whose main component is a relaxation type ferroelectric material, and more specifically, the present invention relates to an electrostrictive element material that has a relaxation type ferroelectric material as its main component, and more specifically, it is capable of generating a large mechanical displacement upon voltage application, has a small voltage-displacement hysteresis, and has high precision. The present invention relates to an electrostrictive element material suitable for voltage-driven displacement elements that require control and have high reliability. [Prior Art] Conventionally, as a new type of drive source to replace the electromagnetic type, for example, a so-called voltage-driven displacement device, which is a functional element that converts electrical energy into mechanical energy by utilizing the electrostriction effect of piezoelectric ceramics, etc. 2. Description of the Related Art Practical use of elements (hereinafter referred to as displacement elements) has been progressing in a wide variety of applications such as minute position control equipment. Furthermore, in recent years, there has been an increasing demand for not only large mechanical displacements but also high-precision control, compactness and weight reduction, and high reliability. For example, as shown in FIG. 3, this type of displacement element is a bimorph structure in which piezoelectric ceramic plates 3 and 3' provided with electrodes are bonded together using an adhesive or the like so as to be sandwiched from both sides by a metal elastic plate 1. The structure is known. When a DC or AC voltage is applied to this displacement element, a mechanical displacement dS ₁ or dS ₂ occurs due to an electrostrictive effect (in this case, a piezoelectric transverse effect). Although this mechanical displacement depends on the application and the mechanism used when mounting it, it is generally desirable that it be as large as possible in terms of its function as a displacement element.
It is said that a composition having a relatively large piezoelectric constant d ₃₁ is advantageous, as represented by the (Ni _1/3 Nb _2/3 )O ₃ -PbZrO ₂ -PbTiO ₃ system. However, in the case of this type of piezoelectric ceramic, even if the mechanical displacement is large, the voltage-displacement hysteresis is large, and this is not necessarily satisfactory for, for example, highly accurate position control. Furthermore, if low hysteresis is emphasized, a decrease in mechanical displacement cannot be avoided due to the material composition. As a new material that compensates for the drawbacks of the piezoelectric ceramic materials described above, an electrostrictive element material having a perovskite structure and containing a relaxation type ferroelectric material as a main component is known. Materials of this kind are, for example, Pb(Mg _1/3 Nb _2/3 )O ₃
- It is made of a PbTiO ₃ -based composition, has a Curie temperature near room temperature, and normally uses a paraelectric phase, and has a relatively small electric field-electrostrictive hysteresis compared to piezoelectric ceramic materials, and does not require polarization treatment. Certain things are said to be one of its main characteristics. [Problem to be solved by the invention] However, in the above electrostrictive element material,
Although highly accurate position control is possible, due to its function as a displacement element, the mechanical displacement is not necessarily sufficient and the range of use is limited, and materials with large mechanical displacement also have large hysteresis and are unsuitable. . In order to eliminate the drawbacks of the above-mentioned electrostrictive element material, the present inventors have made various studies and found that it has the characteristics of large mechanical displacement and low hysteresis.
Pb(Mg _1/3 Nb _2/3 )O ₃ −Pb(Co _1/2 Nb _1/2 )O ₃ −
A new PbTiO ₃ -based composition has been realized (patent application 1986-
No. 13013). Therefore, the technical problem of the present invention is to further improve the dielectric strength while maintaining the above-mentioned characteristics, so that the applied voltage can be selected over a wide range, so that the mechanical displacement can be selected over a wide range. Another object of the present invention is to provide an electrostrictive element material that has high reliability and can be applied to a wider range of uses. [Means for Solving the Problems] That is, the electrostrictive element material of the present invention has the general formula Pb[(Mg _1/3 Nb _2/3 ) _A (Co _1/2 Nb _1/2 ) _B Ti _c ]O ₃ (however, A+B+C=1) 0.700≦A≦0.890,
With respect to the basic composition satisfying 0.010≦B ₂ ≦0.150 and 0.10≦C≦0.15, 0.01 to 0.3% by weight of at least one selected from Sb ₂ O ₃ and CaO and SiO ₂ are added as subcomponents.
It is characterized by containing 0.005 to 0.1% by weight of. In addition, 0.700>A, A>0.890, B>0.150, C>
0.15 and one selected from subcomponents Sb ₂ O ₃ and CaO.
Compositions containing more than 0.3% by weight or more than 0.1% by weight of SiO ₂ result in a decrease in mechanical displacement and an increase in voltage-displacement hysteresis, making them undesirable as intended displacement elements. Also, B<
0.010, for compositions with C<0.100 the mechanical displacement voltage -
No significant improvement effect on displacement hysteresis was observed, and dielectric strength significantly improved in compositions containing less than 0.01% by weight of at least one selected from subcomponents Sb ₂ O ₃ and CaO and less than 0.005% by weight of SiO ₂ . Since no significant improvement was observed, it was excluded from the scope of the present invention. [Example] Examples of the present invention will be described in detail below while comparing with reference examples. PbO, TiO ₂ , MgO, Nb ₂ O ₅ as starting materials,
Co ₂ O ₃ , Sb ₂ O ₃ , CaCO ₃ and SiO ₂ were selected and accurately weighed to give the compositions shown in Tables 1 to 4. Next, after mixing these raw materials in a ball mill,
It was dried and calcined at 700-850°C. Next, an appropriate amount of an organic binder was added to the powder obtained by pulverization using a ball mill, and the mixture was granulated, followed by pressure molding at a pressure of 1 ton/cm ² and firing at a temperature of 1150 to 1250° C. for several hours.
(In addition, at this time, hot pressing treatment was performed as necessary. After cutting the obtained sintered body into a predetermined shape and polishing it, electrodes were applied and various electrostrictive constants were determined by a predetermined measurement method. In order to confirm the effect,
Further polishing and processing make it 35mm long, 10mm wide, and thick.
A rectangular electrostrictive element of 0.14 mm was obtained. The electrostrictive elements 2, 2' were bonded to the metal elastic plate 1 by sandwiching them from both sides to produce a bimorph type displacement element, and the lead terminals were taken out and wired as shown in FIG. After examining the hysteresis and mechanical displacement of the displacement element thus obtained, the maximum applied voltage was measured to examine the dielectric strength. In addition, hysteresis is the mechanical displacement that occurs at the tip when one end is fixed and the other end is free when a 100V DC voltage is applied to the displacement element (dS ₁₀₀ in Figure 2).
It was calculated from the following equation from the residual displacement (the displacement corresponding to dS ₀ in FIG. 2) that occurs when the voltage is returned to zero. Hysteresis=(dS ₀ /dS ₁₀₀ )×100 [%] The mechanical displacement was determined by the free end displacement (dS ₆₀ in FIG. 2) when a DC voltage of 60 V was applied. Further, the maximum applied voltage was determined by applying a DC voltage to the displacement element in increments of 20 V, and the value at which the displacement element was electrically destroyed or the value at which an abnormality was observed in the displacement characteristics. Note that the maximum applied voltage was calculated by converting it into a value when the thickness of the displacement element was 1 mm. Examples of the results are shown in Tables 1 to 4. In Tables 1 to 4, the sample numbers marked with * correspond to the electrostrictive element materials of the present invention. As is clear from Tables 1 to 4, the sample made of the electrostrictive element material of the present invention has a
It is clear that the mechanical displacement, hysteresis, and maximum applied voltage are all good, and that it has favorable characteristics as a displacement element. Thus, according to the present invention, Pb(Mg _1/3 Nb _2/3 )
Pb _[ (Mg _1/3 Nb _{2/3 ) A ( Co 1/2 Nb 1/2} ) _B
By setting the A, B, and C components of the TiO _c ]O ₃ composition within appropriate ranges and adding appropriate amounts of suitable subcomponents, it has high mechanical displacement and low hysteresis characteristics, and is also insulating. This material has a high yield strength and is highly reliable. Although not shown in the examples, 0.01 to 0.3% by weight of Sb ₂ O ₃ and CaO, and 0.005 to 0.1% by weight of SiO ₂ were added to the basic composition of this example as subcomponents. It is clear that the same effects as in this embodiment can be obtained also in this case.

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[Table] [Effects of the Invention] The electrostrictive element material of the present invention can be expected to be applied to a wide range of uses listed below. (1) Since it has a large dielectric strength, it is possible to make the element thinner and generate a large mechanical displacement, and it is possible to be smaller, lighter, and driven at a lower voltage, and can be applied to new fields of displacement elements. (2) Since it has a large dielectric strength, high reliability can be maintained when a predetermined voltage is applied. (3) Since the electrostrictive element itself has no polarity, it is easy to handle when configured as a bimorph (one-sided drive system), and the magnitude of the applied voltage can be selected from a wide range, making it suitable for mechanical Displacement can be set. (4) It has high reliability with very little mechanical displacement movement (displacement shift) even when voltage is applied for a long time. It is fully applicable to equipment. (5) Because of its high dielectric strength, it can be applied to applications that require large displacements due to the application of high voltage. (6) In addition to being used as a displacement element, it can be substituted with various piezoelectric products as needed. In the embodiments of the present invention, mechanical displacement, voltage-displacement hysteresis, and dielectric strength were explained in particular in relation to a bimorph type displacement element, but in the case of a laminated structure using the electrostrictive element material according to the present invention. The present invention has also been investigated and its improvement effect has been confirmed. Therefore, it is fully possible to apply the method to, for example, a laminated displacement element, and to make the laminated displacement element smaller and lighter. As described in detail above, the electrostrictive element material of the present invention is suitable for displacement elements that can be used in a wide range of applications, and is extremely valuable industrially.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of a bimorph type displacement element used for evaluation in an embodiment of the present invention, Fig. 2 is a graph showing measurement standards in an embodiment of the present invention, and Fig. 3 is a conventional FIG. 3 is a diagram showing an example of a bimorph type displacement element. In the figure, 1... metal elastic plate, 2, 2'... electrostrictive element, 3, 3'... piezoelectric ceramic plate.

Claims (1)

[Claims] 1 General formula Pb [(Mg _1/3 Nb _2/3 ) _A (Co _1/2 Nb _1/2 ) _B Ti _c ]
O ₃ (however, A+B+C=1) 0.700≦A≦
For the basic composition satisfying 0.890, 0.010≦B2≦0.150, 0.10≦C≦0.15, Sb ₂ O ₃ and CaO are added as subcomponents.
An electrostrictive element material characterized in that it contains 0.01 to 0.3% by weight of at least one selected from the following and 0.005 to 0.1% by weight of _SiO2 .