Hydrogen-free, one-step solid-phase fabrication of high-performance CsₓWO₃ nanopowders for energy-saving coatings

The development of spectrally selective materials with high visible-light transparency and near-infrared (NIR) absorption is vital for energy-saving windows. Conventional solid-phase synthesis of cesium tungsten bronze ( CsₓWO₃ ) often relies on explosive H2 gas, posing significant safety risks and hindering scalable production. This work presents a safe, hydrogen-free, one-step solid-phase method to synthesize CsₓWO₃ nanopowders using tungsten powder as a reducing agent. By optimizing Cs/W molar ratios (0.32:1) and sintering temperatures (500–600 °C), we achieved phase-pure CsₓWO₃ nanoparticles (<100 nm) at 550 °C with enhanced NIR shielding. The W-9 series (n(Cs):n(W₁):n(W₂) = 0.32:0.1:0.9) exhibited superior solar energy transmittance selectivity (SETS = 0.776) and 95% NIR shielding efficiency, outperforming cellulose-reduced counterparts. This method not only eliminates explosive H₂ risks, enhancing process safety and scalability, but lowers processing temperatures, enabling scalable production of high-purity CsₓWO₃ for energy-saving coatings.