Internal stress and dislocation-mediated phase structure and conduction mechanism in flash-sintered Na1/2Bi1/2TiO3-based ceramics

Abstract

Na_1/2Bi_1/2TiO₃ (NBT) is widely regarded as a multifunctional material, exhibiting dual capabilities as both an insulating piezoelectric material and an oxygen ion conductor. Historically, property tuning has predominantly relied on chemical doping to tailor composition and phase structure. Here, 0.94(Na_0.5Bi_0.5TiO₃)–0.06BaTiO₃ (NBT-6BT) ceramics were prepared by flash sintering. X-ray diffraction and scanning electron microscopy analyses indicate that the flash-sintered sample exhibit a heterogeneous grain morphology and features a high internal stress, which drives a rhombohedral-to-tetragonal transition and enhances ferroelectric behavior. Notably, transmission electron microscopy reveals dislocations within the ceramics. Furthermore, impedance spectroscopy demonstrates ionic conductivity in undoped, flash-sintered NBT-6BT ceramics. Molecular dynamics (MD) simulations demonstrates that the enhanced ionic conductivity is associated with dislocation-induced pathways for oxygen diffusion. By showing that stress and dislocation engineering can effectively tune both structural and electrical properties without additional compositional modification, this study presents a compelling alternative to conventional chemical doping strategies for piezoelectric ceramics.