Mn2+-doping and Vacancy Engineering Induce Phase Transition with Ultrahigh Dielectric Switching Ratio in Lead Chloride Hybrids

Abstract

Lead halide hybrids are promising switchable dielectric materials owing to their structural tunability, which enables thermotropic phase transitions. However, achieving large dielectric contrasts remains a significant challenge. Here, we demonstrate a strategy to markedly enhance the dielectric switching ratio (DSR) by engineering a phase-transition compound with elevated ionic conduction in the high-temperature phase via vacancy-enabled ionic transport. Using [C₅H₁₂N]₂PbCl₄ (C₅H₁₂N⁺ = piperidinium) as a model, we synthesized a series of [C₅H₁₂N]_2-2xPb_1-xMn_xCl_4-2x (x = 0.01–0.15) via solvent-free mechanochemistry. Mn²⁺-doping introduces charge-compensating C₅H₁₂N⁺ and Cl⁻ vacancies into the lattice, triggering a structural phase transition. As anticipated, the doped hybrids exhibit substantially improved DSR, with the x = 0.15 composition reaching an ultrahigh value of ~10³-surpassing most reported dielectric switching materials. This enhancement is attributed to a grain boundary-induced barrier layer mechanism within the ion-conducting system. Our results establish vacancy-enabled ionic transport as a viable strategy for designing high-performance dielectric switching materials within soft halide frameworks.