Greatly enhanced electrical resistivity in La3Ta0.5Ga5.3Al0.2O14 high temperature piezoelectric crystal through microscopic defect engineering

Abstract

Enhancing the electrical resistivity of piezoelectric crystals is essential for improving the sensing capability of high temperature piezoelectric sensors, especially at low frequency range. In this work, we investigated the conduction mechanism of the La₃Ta_0.5Ga_5.3Al_0.2O₁₄ (LTGA) crystal and elucidated the role of intrinsic defects in electrical resistivity. Our findings indicate that the conductive behaviors are closely related to the point defects, such as oxygen vacancy and Al_Ta antisite defects, in LTGA crystal. The dominant Al_Ta antisite defects facilitate carrier migration, and make hole carrier emission easier due to the small lattice distortion among the Al_Ta antisite defects with different valence states. In contrast, electrons are less likely to be trapped, preventing the formation of electron-hole complex centers, thereby increasing hole concentration and electrical conductivity. Interestingly, the oxygen vacancy concentration can modulate the formation energy of Al_Ta antisite defects, thus influencing electrical resistivity. A higher concentration of oxygen vacancy results in fewer Al_Ta antisite defects, thus the higher electrical resistivity. By inhibiting the formation of Al_Ta antisite defects through crystal growth in a low-oxygen atmosphere, we successfully obtained high quality LTGA crystal with two-order of magnitude increase in electrical resistivity.