Crystal growth and electromechanical properties of A1 substituted langasite (La₃Ga_5-xAl_xSiO₁₄)

Al-substituted langasite (La₃Ga_5-xAl_xSiO₁₄) single crystals up to x = 0.9 have been grown by the Czochralski method. The effective segregation coefficient (k_eff) of A1 in langasite was estimated to be between 1.03 and 1.07. X-ray structural analysis indicated that A1 occupied the octahedral and the two kinds of tetrahedral sites in the crystal lattice. The piezoelectricity of A1-substituted langasite was also compared with that of langasite. By A1 substitution, while the piezoelectric constant |d₁₁\ became slightly larger, d₁₄ was smaller. The electromechanical coupling factors (k₁₂, k₂₅ and k₂₆) became larger. It was found that A1 substitution of langasite created a material with preferred electromechanical properties applicable to the next generation of advanced digital communication systems.