Density functional theory and experimental study on the optical properties of calcium tungsten bronze

The alkaline earth metal tungsten bronze Ca_0.1WO₃ was successfully synthesized using the solid-state reaction method. XRD, SEM, and TEM analyses confirmed the good crystallinity of the material, although severe particle aggregation was observed. Optical property tests revealed low absorption and reflection in the visible light region, and higher values in the near-infrared region for Ca_0.1WO₃. XPS measurements and DFT theoretical calculations suggested that the introduction of Ca ions transformed WO₃ from a semiconductor to a metallic state, with partial reduction of hexavalent W to pentavalent W. This introduced additional free electrons to the material, resulting in localized surface plasmon resonance (LSPR) effects under incident light, significantly enhancing its near-infrared absorption performance. These characteristics of alkaline earth metal tungsten bronze make it a potential candidate for transparent thermal insulation materials.