Relationship between crystal structure and acoustic physical properties of Ca3B(Ga,Al)3Si2O14 [B = Nb, Ta] piezoelectric single crystals

The crystal structures of Ca3Nb(Ga,Al)3Si2O14 (CNGAS) and Ca3Ta(Ga,Al)3Si2O14 (CTGAS) single crystals are investigated in this study to reveal the relationship between their crystal structures and acoustic physical properties. The positional parameters of each element for the CNGAS and CTGAS single crystals are determined with high accuracy, whereas the bond lengths and bond angles are calculated using the positional parameters. Analysis results of the crystal structures suggest that the increase of bond angles, O2-Si-O2 and Si-O2-(Ga,Al), in the O2-Si-O2-(Ga,Al) line causes the increase of their anisotropy of crystal structures. Elastic constants related to the z-axis, i.e., cE33 and cE44, increase significantly after Al substitution, which is attributed to the increase in the anisotropy of the crystal structures.