| 摘要 |
PURPOSE:To improve the temperature stability of an electrostrictive element, and to improve accuracy by applying specific voltage on conversion into an electric field to the electrostrictive element. CONSTITUTION:An electrostrictive element is constituted of an electrostrictive material, the phase transition temperature of paraelectric phase and ferroelectric phase thereof extends over a value in the vicinity of a working temperature or less, and a voltage exceeding Em represented in formula on conversion into an electric field is applied to the electrostrictive element. The phase transition temperature of the paraelectric phase and the ferroelectric phase extends over the value in the vicinity of the working temperature or less in the electrostrictive material being used, and the electrostrictive material is limited to a material having the ferroelectric phase at a temperature sufficiently lower than the working temperature. Such a material generally has large electrostriction because it has a large dielectric constant. Since the relationship of the electric field and electrostriction displays large hysteresis in a material, the phase transition temperature thereof is considerably higher than the working temperature, the material is limited to a material, the phase transition temperature thereof is higher than the working temperature by 20 deg.C at the most, and it is desirable that the phase transition temperature is lower than the working temperature.
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