Study on thermochromic-emissivity performance of Mn doped TiO2 under temperature fluctuations

Abstract

In this work, Mn doped TiO2 powders were synthesized directly by a solid state reaction route. Thermal treatment of the samples was carried out in air at temperatures from 800 °C to 1200 °C. Mn doped TiO2 powders have been structurally characterized by XRD, SEM and XPS, which indicates that as-prepared samples have the rutile phase structure and Mn ions are +2 and +3 state in rutile TiO2 after thermal treating at 800 °C −1200 °C. The band gap for Mn doped TiO2 powders was measured by UV–Vis absorption spectra, and these results found that the band gap shown a decreasing trend from 3.14 eV to 1.70 eV with the annealing temperature increasing. The reversible thermochromic phenomenon is attributed to the electrons in color centers absorbing the visible light. Variable emissivity property is connected with the morphology, electrical resistivity as well as lattice vibration of Mn doped TiO2 samples. The results demonstrated that heat treatment is a powerful avenue to improve the thermochromic-emissivity performance for Mn doped TiO2 materials.