Cesium tungsten bronze (Cs_xWO₃) powders were synthesized by hydrothermal reaction at 190 °C by using sodium tungstate and cesium carbonate as raw materials, and the effects of N₂ annealing on the microstructure and near-infrared (NIR) shielding as well as heat insulation properties of Cs_xWO₃ were investigated. The results indicated that the synthesized Cs_xWO₃ powders exhibited hexagonal Cs_0.32WO₃ crystal structure, and subsequent N₂ annealing could further improve the crystallinity of Cs_xWO₃ particles.

Moreover, the NIR shielding and heat insulation properties of Cs_xWO₃ could be further improved after N₂ annealing at appropriate temperature for a period of time. Particularly, the 500 °C-annealed Cs_xWO₃ products in the N₂ atmosphere showed the best NIR shielding and heat insulation properties. When the N₂ annealing temperature was higher than 700 °C, the NIR shielding properties decreased again. The 800 °C-annealed samples in the N₂ atmosphere showed higher visible light transmittance, however, the NIR shielding properties were lower than that of the non-annealed samples.