Study on the Mechanism of Phase Transition of VO₂ with Low-Concentration W Doping

As a phase transition material, the application of VO₂ is hindered by its phase transition temperature which is higher than room temperature, and elemental doping is an effective method to modulate the phase transition temperature. Here, we synthesized pure and W-doped VO₂ via a hydrothermal method. The crystal structures, morphology, and phase transition behaviors were characterized by x-ray diffraction, field-emission scanning electron microscopy and differential scanning calorimetry measurements, respectively. The temperature of the phase transition sharply decreased from 67.5°C down to 8.5°C by 3 at.% W doping. We also performed first-principles calculations to explore the atomic and electronic structures of pure and W-doped VO₂. We found that V atoms along the c axis in the W-doped R-phase structure paired and tilted to form a V dimerized structure similar to the M₁ phase. Significant modifications in the electronic structures of W-doped VO₂ were also observed, collectively reducing the energy barrier for the phase transformation, leading to the observed decrease in transition temperature. The metal-insulator transition temperature (T_MIT) decreased with increasing doping concentration. Our theoretical investigations provided a deeper interpretation of the mechanism underlying the T_MIT changes induced by W doping.