Manipulating the metal-to-insulator transitions of VO₂ by combining compositing and doping strategies

Vanadium dioxide (VO₂) exhibits the most abrupt metal-to-insulator transition (MIT) property near room temperature among the representative 3d-orbital correlated oxides, and its structural variation during the MIT usually results in poor mechanical properties as bulk pellets. Moreover, compositing with highly resistive oxides has been reported to improve the mechanical strength of bulk VO₂ since the generation and propagation of microcracks is suppressed upon thermocycling across the MIT; further, their respective impacts on electrical transportation are yet unclear. Herein, we demonstrate the role of these highly resistive oxide composites (e.g., HfO₂, CoO and Al₂O₃) in reducing charge leakage along the microcracks within the insulating phase of VO₂, leading to more abrupt MIT properties from the perspective of electrical transportation. This enables the possibility of simultaneously regulating the critical temperature and abrupt MIT transition, as well as the mechanical properties of the VO₂ bulk pellets via compositing with oxides with different melting points using spark plasma-assisted reactive sintering (SPARS).