Synthesis and phase transition properties of VO 2 (M) hollow spheres with large thermal hysteresis width

Abstract

Thermochromic VO 2 (M) has attracted increasing attention regarding the reduction of its thermal hysteresis width (Δ T c ). However, little attention is paid to increase its Δ T c , which may have scientific importance and potential application in the future. Herein, VO 2 (M) hollow spheres assembled by nanoparticles are successfully synthesised using NH 4 VO 3 as the vanadium source by a template-free method. Their diameters mainly range from 350 to 650 nm and thickness of shells is about 50 nm in average. The hydrothermal process plays a crucial role in the successful formation of VO 2 (M) hollow spheres. The phase transition temperature ( T c ) of VO 2 (M) hollow spheres is about 63°C in the heating curve and 32°C in the cooling curve. The Δ T c of VO 2 (M) hollow spheres reach as high as 31°C, which is distinctively higher than the reported values (ca. 5-20°C). The huge Δ T c may have potential applications in some fields in the future.