Thermal-Induced Dielectric Switching with 40K Wide Hysteresis Loop Near Room Temperature

A thermal-induced dielectric switching has been realized in two ion-pair crystal [C₂H₆N₅]⁺·[H₂PO₄]^- (1, C₂H₆N₅ = 3,5-diamino-1,2,4-triazolinium) through single-crystal-to-single-crystal phase transition (SCSC-PT). Upon cooling from room temperature, the 1D cation stripes that are composed of [C₂H₅N₅]⁺ cations have undergone a 90° sharp rotation around the c axis, accompanied by the transition of crystal stacking from loose unparallel (dynamic state) to compression parallel (static state) and reorientation of dipoles on the [C₂H₅N₅]⁺ cation, which thus resulted in high dielectric state to low dielectric state transformation. While on the warming run, the reverse process was rather sluggish, resulting in a reversible dielectric switching with ultralarge (about 40K wide) hysteresis loop near room temperature. It is thought that the large-sized polar cation stripes have a predominant influence on the switching properties of 1.