Tungsten bronze Cs_xWO₃ nanopowders doped by Ti to enhance transparent thermal insulation ability for energy saving

Cesium tungsten bronze (Cs_xWO₃), a unique energy-saving material, has attracted great interest because of its excellent visible transmittance and near-infrared absorption. In order to improve its optical properties, the Ti doping modification was carried out in this work, and a series of Ti-doped Cs_XWO₃ (Ti-Cs_xWO₃) nanopowders were synthesized by a solvothermal reaction and post-annealing. The 1.71 at. % of Ti dopants achieved remarkable enhancement of both integral visible transmittance (T_lum, 380–780 nm) and near-infrared shielding efficiency (Ψ_NIR, 780–2500 nm) of Cs_xWO₃. The T_lum and Ψ_NIR of the 1.71 at. % Ti-Cs_xWO₃ polymer film reaches 63.87 % and 76.90 %, respectively, higher by 51.88 % and 65.00 % than those of the Cs_xWO₃ film. The improvement of T_lum is attributed to the broadening of band gap and smaller size of the nanoparticles induced by Ti doping, and the enhanced Ψ_NIR would result from the increased free electron concentration and energy levels of impurities. The incorporation of Ti elements renders Cs_xWO₃ a promising application in the field of energy saving.