Growth of 3-inch langasite single crystal and its application to substrate for surface acoustic wave filters

Macro defect-free langasite (La₃Ga₅SiO₁₄) of 3″ diameter was grown by the Czochralski technique. Thermal treatment of the melt and a uniform interface shape are important for langasite growth with a clear habit of faceting. The homogeneity in composition was two-dimensionally investigated by X-ray diffraction analysis and SAW (surface acoustic wave) velocity distribution on the wafer fabricated from the crystal. The deviation was sufficiently small for the use of langasite as a suitable substrate in SAW device applications. SAW properties were calculated based on the available material constants.