Crystal growth and piezoelectric properties of Ca3Ta(Ga1−x Scx)3Si2O14 single crystals

Ca3Ta(Ga1-xScx)3Si2O14 (CTGSS) single crystals with various Sc concentrations (x = 0, 0.1, 0.2, 0.3, and 0.4) were grown by the micro-pulling-down method and their structure and chemical composition were evaluated. Through the powder X-ray diffraction (XRD) measurement and backscattered electron (BSE) imaging, it was demonstrated that all the CTGSS crystals with different Sc concentration were successfully grown as langasite-type structure although some secondary phases were observed for the crystals with x = 0.2, 0.3 and 0.4. Lattice parameters calculated from the powder XRD pattern generally increased with Sc substitution. Measured parameters for CTGSS crystal with x = 0.1 were larger permittivity ε11T/ε0 and lower electromechanical coupling coefficient k12 and piezoelectric constant d11 than those for CTGS crystal with x = 0. It was also suggested that piezoelectric constant |d14| became larger due to the Sc substitution.