The influences of aluminum substitution for gallium in the langasite-type La 3Nb 0.5Ga 5.5O 14 (LNG) crystals on their growth and electric properties were investigated. Al-substituted LNG (La 3Nb 0.5Ga 5.5− x Al x O 14; LNGA x) single crystals up to the solubility limit x = 0.2 have been grown by the conventional Czochralski technique. The electric properties of the LNGA x crystals were investigated and compared to those of LNG. With Al substitution, the piezoelectric constants, d 11 and d 14, were slightly higher. The LNGA x crystals showed a temperature dependence of d 11 similar to that of the LNG crystal.