GALLATE SINGLE CRYSTAL, PROCESS FOR PRODUCING THE SAME, PIEZOELECTRIC DEVICE FOR HIGH-TEMPERATURE USE AND PIEZOELECTRIC SENSOR FOR HIGH-TEMPERATURE USE

摘要

It is an object of the present invention to provide a material for a piezoelectric device used at a high temperature zone, which can be used at the high temperature zone exceeding 400°C and has a resistivity whose temperature dependence is low. The material is characterized by having a composition selected from the group consisting of RE3Ga5-xAlxSiO14 (wherein RE represents a rare earth, and 0x5), RE3Ta0.5Ga5.5-xAlxO14 (wherein RE represents a rare earth, and 0x5.5) and RE3Nb0.5Ga5.5-xAlxO14 (wherein RE represents a rare earth, and 0x5.5), and characterized in that a resistivity change at the temperature zone of 100 to 600°C is 104 or less. The material is characterized by being produced by growing a single crystal from a solution in an atmosphere of inert gas containing an oxidative gas, and subsequently cooling the single crystal with lowering a molar fraction (z) of the oxidative gas in the inert gas below a molar fraction of the oxidative gas in the growing step.