Ultralarge Dielectric Relaxation and Self-Recovery Triggered by Hydrogen-Bonded Polar Components

Subtle integration of rotatable polar components into dielectric crystals can contribute significantly to adjustable switching temperatures (Ts) and dielectric relaxation behaviors. Currently, one of the biggest challenges lies in the design of optimal polar components with moderate motion resistance in a crystalline system. In this work, we demonstrate that under refrigerator conditions, rotatable hydrogen-bonded one-dimensional (1D) cationic chains, {[C2H6N5]+}n (C2H6N5 = 3,5-diamino-1,2,4-triazolinium), and two-dimensional (2D) anionic layers, {[(H2O)2·SO4]2–}n, can be generated in an organic salt, 3 ([C2H6N5]2·[(H2O)2·SO4]). Compared with the nonhydrated precursor, 2 ([C2H7N5]·[SO4]), the rotation of these 1D and 2D ionic species triggers a reversible phase transition and dielectric switching in 3. In addition, the significantly sluggish rotation of the 1D cationic chains from parallel to unparallel stacking and the counter-clockwise rotation of the 2D anionic layers, compared with their reverse processes, induce a frequency-dependent dielectric response with a more highly adjustable heating Ts↑ than the cooling Ts↓. More importantly, 3 possesses excellent self-recovery ability attributed to the highly dynamic character of the hydrogen-bonded ionic species. The strategy here can provide a fairly good model for designing dielectric crystals with desired rotatable polar components.