Continuous crystal growth and homogeneity of 2-inch Ca₃Ta(Ga,Al)₃Si₂O₁₄ bulk single crystals

Langasite-type Ca₃Ta(Ga,Al)₃Si₂O₁₄ (CTGAS) piezoelectric bulk single crystals with a 2-inch diameter were continuously grown by the Czochralski (Cz) method using the residual melt after crystal growth and recharging. The first and second bulk single crystals without cracks were grown using a continuous crystal growth process. However, the third bulk single crystal included many cracks, suggesting that the cracks were generated because of the change in melt composition by the recharging process originating from the difference between the stoichiometric and congruent compositions. By evaluating the velocity distribution using ultrasonic waves, an area with low leaky surface acoustic wave (LSAW) velocity was observed at the center of the bulk single crystal.