In order to further improve the near-infrared shielding properties of cesium tungsten bronze (Cs_xWO₃) for solar filter applications, Cs_xWO₃ particles were prepared by solvothermal reaction method and the effects of nitrogen annealing on the microstructure and near-infrared shielding properties of Cs_xWO₃ were investigated. The obtained Cs_xWO₃ 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 Cs_xWO₃ particles with hexagonal structure began to transform into nanorods after annealed at temperature higher than 600 °C. The near-infrared shielding properties of Cs_xWO₃ particles could be further improved by N₂ annealing at 500–700 °C. Particularly, the 500 °C-annealed Cs_xWO₃ 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 Cs_xWO₃ samples is correlated with its minimum O/W atomic ratio and most oxygen vacancies.