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 RE 3 Ga 5-x Al x SiO 14 (wherein RE represents a rare earth, and 0<x<5), RE 3 Ta 0.5 Ga 5.5-x Al x O 14 (wherein RE represents a rare earth, and 0<x<5.5) and RE 3 Nb 0.5 Ga 5.5-x Al x O 14 (wherein RE represents a rare earth, and 0<x<5.5), and characterized in that a resistivity change at the temperature zone of 100 to 600°C is 10 4 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.