Discovery and evolution of double P‐E loops in a tetragonal Fe‐doped KTa_0.57Nb_0.43O₃ single crystal

Abstract

Double polarization‐electric field (P‐E) loops were observed in Fe‐doped KTa0.57Nb0.43O3 (Fe‐KTN) crystals because of the restraining effect of the defect dipoles on domain reorientation. In Fe‐KTN crystals, the positively charged O2− vacancies and negatively charged dopant Fe3+ ions form defect dipoles, providing a restoring force for domain reorientation. Moreover, built‐in macro‐polarization was observed depending on the orientation of the defect dipole polarization. The response of the defect dipoles to an external electric field and the evolution of the double P‐E loops were investigated. The restraining effect of the defect dipoles on domain reorientation was found to affect normal piezoelectric activities. The domains could maintain the state close to the polarization direction, resulting in an extremely high d33 value (287 pC/N).

Evidence of double-loop hysteresis in disordered ferroelectric crystal

“…13 Furthermore, in perovskites of the same family, defect content and features can be used to program the hysteretic behavior of polarization-field paths. 14,16 The correlated PNRs are believed to become dominant when the system undergoes specific thermal trajectories in correspondence to the diffuse transition region, which is typical of relaxors. 2,10,15,19,[25][26][27][28][29][30] As in other glass-forming systems, the response of near-transition disordered ferroelectric samples is affected by the cooling or heating rate so that specific effects are observed only for a sufficiently rapid cooling or heating to the operating temperature.…”