Single-crystal growth of langasite (La 3Ga 5SiO 14) by the vertical Bridgman (VB) method in air and in an Ar atmosphere

Piezoelectric langasite (La 3Ga 5SiO 14, LGS) single crystals were grown by the vertical Bridgman (VB) method in air and in an Ar atmosphere. In the Ar atmosphere, a colorless-transparent crack-free LGS single crystal, 1 in. in diameter, was grown using raw material with a slightly Ga-rich composition, while in air an orange-colored transparent LGS crystal was grown. Any other phases could not be detected in the crystals, which may suggest that only a few Ga atoms evaporated from the melt during the growth in an Ar atmosphere. The resistivity of an LGS crystal grown in an Ar atmosphere was higher than that grown in air.