Issue 56, 2016, Issue in Progress

An abnormal phase transition behavior in VO2 nanoparticles induced by an M1–M2–R process: two anomalous high (>68 °C) transition temperatures

Abstract

Vanadium dioxide (VO2) has a reversible metal–insulator transition (MIT) at 68 °C and can be used to develop thermally and electrically sensitive devices. In this study, an abnormal phase transition behavior of VO2 nanoparticles was discovered during the comparison of pristine nanoparticles without and with high temperature thermal treatment. The single phase transition temperature at 65.1 °C for the pristine VO2 nanoparticles split into two temperatures at approximately 74 °C (T1) and 84 °C (T2) after thermal treatment at 400 °C for 6 h. Both temperatures are much larger than 68 °C. Through characterization by Raman and transmission electron microscopy (TEM), the two higher transition temperatures could be well explained by the formation of VO2 (M2). Grain boundaries were observed during the merger and fusion processes of VO2 nanoparticles at high temperatures. The grain boundaries and interfacial defects resulted in the dislocation of the lattice structure and produced stress and strain in the VO2 nanoparticles. Consequently, VO2 (M2) with a higher temperature formed in the heating process and the initial MIT (M1–R) became an M1–M2–R transition. Moreover, the thermal treatment improves the phase transition enthalpy (ΔH) of VO2, which promotes the increase in the solar modulation ability (ΔTsol) of VO2–PET composite film from 12.8% to 15.2–17.0% without loss in the luminous transmittance. These findings are of great significance to the deep understanding of MIT and the development of VO2 smart windows.

Graphical abstract: An abnormal phase transition behavior in VO2 nanoparticles induced by an M1–M2–R process: two anomalous high (>68 °C) transition temperatures

Article information

Article type
Paper
Submitted
16 Mar 2016
Accepted
04 May 2016
First published
09 May 2016

RSC Adv., 2016,6, 50521-50528

Author version available

An abnormal phase transition behavior in VO2 nanoparticles induced by an M1–M2–R process: two anomalous high (>68 °C) transition temperatures

B. Dong, N. Shen, C. Cao, Z. Chen, H. Luo and Y. Gao, RSC Adv., 2016, 6, 50521 DOI: 10.1039/C6RA07009D

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