Van Der Waals Order–Disorder Type Ferroelectric VOCl 2 with Unusual Polarization Switching

Harnessing atomic ordering through order–disorder transition is a powerful strategy to tailor electric polarization and functionality. However, most reported order–disorder ferroelectrics exhibit low Curie temperatures, narrow thermal hysteresis, and limited tunability, restricting their potential in nonvolatile memory technologies. Here, we identify VOCl2 as a new van der Waals order–disorder ferroelectric with site disorder, exhibiting an exceptionally wide thermal hysteresis (ΔT = 220 K) and a high Curie temperature (Tc = 440 K), associated with lattice expansion across the disorder to order transition. Moreover, the sensitivity of V4+ cations to structure distortions allows efficient polarization tuning under hydrostatic pressure, where pressure irreversibly induces the in-plane polarization at 2.3 GPa, and then drives a reversible polarization switching from in-plane to out-of-plane at 8.0 GPa. Such a giant thermal hysteresis and unusual polarization switching of VOCl2 open new opportunities for programmable phase-change devices with a broad operating window.