Atomistic configurational effects on piezoelectric properties of La3Ta0.5Ga5.5O14 and a new piezoelectric crystal design

Abstract Single crystalline langatate (LTG, La 3 Ta 0.5 Ga 5.5 O 14 ) has been widely used as a sensor material in high temperature applications because of its thermally stable piezoelectric properties. In this research, to elucidate the relationship between piezoelectric tensors and local ionic configurations, first-principles calculations based on density functional perturbation theory (DFPT) were performed on various local ionic structures. The results indicate that two independent relaxed-ion piezoelectric coefficients, e 11 and e 14 , increased with increases in La ( 3e ) –O and Ta ( 1a ) –O distances or decreases in Ga ( 3f , 2d ) –O distances. Thus, to obtain high piezoelectric constants in this crystal, ions larger than La 3+ should be incorporated at 3e sites to open the distance between 3e ions and oxygen ions, and ions smaller than Ga 3+ should be introduced at 2d and 3f sites to reduce the distance between Ga and O ions. Finally, from this design rule, a new crystal, BTAS (Ba 3 TaAl 3 Si 2 O 14 ), which belongs to the same P321 group, is proposed. The calculated relaxed-ion piezoelectric coefficient e 11 of BTAS was 17.7% higher than the coefficient of a LTG crystal. This significant increase confirms BTAS as a useful new piezo-material, especially in applications where there is also a need to reduce the use of more expensive elements.