Origin of high piezoelectricity of a bismuth-based organic–inorganic hybrid crystal

Abstract

Bismuth-based piezoelectric materials have emerged as promising piezoelectric systems owing to their high Curie temperature, large spontaneous polarization, low toxicity and environmentally friendly nature. The origin of the piezoelectric properties of organic hybrid crystals is different from that of traditional inorganic piezoelectric ceramics. To have an insightful understanding of the effects of crystal structure on the fundamental physical performance such as the piezoelectric properties, here, we fabricated a bismuth-based single crystal with a chiral nature with the strategy of chiral ligand induction. As a result of the hydrogen-bonding synergetic charge transfer between the organic and inorganic components, huge polarization along the b-axis was generated as predicted theoretically. Though a sizeable d₃₃ coefficient and phase transition temperature (T_c) were not acquired due to the limitation of crystal growth orientation, a large shear piezoelectric coefficient of 46.54 pC N⁻¹ with an electromechanical coupling coefficient over 40% were demonstrated by a dynamic method. In addition, a special “phase transition” and marked thermal contraction were detected, which were affirmed to be a caloric effect caused by the breaking of the Bi–Br bonds and the lattice contraction. The recrystallized single crystal retained its chiral P2₁ space group, while the shortened bond length and the increased bond angle in the reformed structure caused a stronger distortion of the inorganic skeleton and enhanced intermolecular interactions between the organic molecules and inorganic skeleton, therefore enhanced ferroelectric and piezoelectric properties are expected for the reformed crystal after heat-treatment.