Nanocrystalline CsxWO3 particles: Effects of N2 annealing on microstructure and near-infrared shielding characteristics

In order to further improve the near-infrared shielding properties of cesium tungsten bronze (CsxWO3) for solar filter applications, CsxWO3 particles were prepared by solvothermal reaction method and the effects of nitrogen annealing on the microstructure and near-infrared shielding properties of CsxWO3 were investigated. The obtained CsxWO3 samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and spectrophotometer. The results indicate that nanosheet-like CsxWO3 particles with hexagonal structure began to transform into nanorods after annealed at temperature higher than 600 °C. The near-infrared shielding properties of CsxWO3 particles could be further improved by N2 annealing at 500–700 °C. Particularly, the 500 °C-annealed CsxWO3 samples in the N2 atmosphere showed best near-infrared shielding properties. It was suggested that the excellent near-infrared shielding ability of the 500 °C-annealed CsxWO3 samples is correlated with its minimum O/W atomic ratio and most oxygen vacancies.