Growth and piezoelectric properties of Ca 3 Nb(Ga 1− x Al x ) 3 Si 2 O 14 ( x = 0.25 and 0.50) single crystals

One inch Ca 3 NbGa 3 Si 2 O 14 (CNGS) and Ca 3 Nb(Ga 1− x Al x ) 3 Si 2 O 14 (CNGAS) bulk crystals with an ordered langasite-type structure were grown by a Czochralski method. CNGS bulk single crystals without cracks could be grown, while CNGAS bulk crystals with x = 0.25 and 0.50 included some cracks even under improved growth conditions. Lattice parameters and anisotropy on the structure of grown crystals were systematically decreased and increased by increasing the Al concentration, respectively. Although the density and dielectric constant ε 11 of an X -cut sample of the CNGAS crystal with x = 0.25 were decreased by Al substitution, the electromechanical coupling factor k 12 and piezoelectric constant d 11 were increased. The effects of Al substitution on piezoelectric properties were almost consistent with previous reports on the disordered langasite-type crystals except for their amount of change.