Gallate single crystal, process for producing the same, piezoelectric device for high-temperature use and piezoelectric sensor for high-temperature use

摘要

A material for high-temperature region piezoelectric device that can be used at a high temperature zone exceeding 400 DEG C, having a resistivity whose temperature dependence is slight. The material is characterized by having a composition selected from the group consisting of RE3Ga5−xAlxSiO14 (wherein RE represents a rare earth, and 0<X<5), RE3Ta0.5Ga5.5−xAlxO14 (wherein RE represents a rare earth, and 0<X<5.5) and RE3Nb0.5Ga5.5−xAlxO14 (wherein RE represents a rare earth, and 0<x<5.5) and by exhibiting a 100 to 600° C. resistivity change of ≦̸104. The process for producing the same is characterized by growing a single crystal from a solution in an atmosphere of inert gas containing an oxidative gas and thereafter cooling the single crystal in an inert gas whose oxidative gas molar fraction (z) is lower than in the above growing step.