Dielectric and piezoelectric anisotropy of lithium niobate and lithium tantalate single crystals

The dielectric and piezoelectric coefficients of lithium niobate (LiNbO ₃ ) and lithium tantalite (LiTaO ₃ ) single crystals have been theoretically calculated and experimentally measured for different cutting orientation directions. For LiNbO ₃ and LiTaO ₃ , the measured effective dielectric epsiv ₃₃ and piezoelectric d ₃₃ exhibit the same trend with the calculated ones in YOZ plane. Their longitudinal piezoelectric coefficient d ₃₃ can be enhanced greatly near 60deg direction canted away from the rhombohedral direction. The enhancement of longitudinal piezoelectric coefficient d ₃₃ along a nonpolar direction can be understood as a consequence of the large shear piezoelectric coefficients.