Piezoelectric strain coefficients in La3Ga5.3Ta0.5Al0.2O14 and Ca3TaGa3Si2O14 crystals

Independent piezoelectric strain coefficients d11 and d14 in disordered La3Ga5.3Ta0.5Al0.2O14 (LGTA) and ordered Ca3TaGa3Si2O14 (CTGS) crystals of the langasite family were measured by high-resolution X-ray diffraction (HRXRD) under external electric field application which causes changes in the interplanar spacing because of the reverse piezoelectric effect. The experiment showed that the piezoelectric strain coefficients can be precisely determined by measuring changes in the interplanar spacing using the optical scheme of a triple-axis X-ray diffractometer. The measured independent piezoelectric strain coefficients d11 and d14 for LGTA and CTGS crystals are d11(LGTA) = 6.455 × 10−12 C/N, d14(LGTA) = −5.117 × 10−12 C/N; d11(CTGS) = 3.330 × 10−12 C/N, d14(CTGS) = −15.835 × 10−12 C/N.