Influence of strain on latent heat of VO2 ceramics

Vanadium dioxide (VO2), which undergoes a metal-insulator transition (MIT) at 67 °C, is an attractive material for caloric applications, possessing a latent heat comparable to that of ice-water. Here, we have investigated the variation in latent heat due to residual strain induced by spark plasma sintering (SPS). SPS pressure linearly increased the degree of inhomogeneous strain, thereby reducing the latent heat and broadening the MIT temperature range. Optical observation of MIT revealed a slow transition in highly strained samples. Moderate annealing of highly strained VO2 can eliminate this strain, and thereby recover the high latent heat. The present study indicates the importance of strain tuning for the utilization of intrinsic latent heat in VO2 ceramics.