Abstract:

Tungsten bronze coatings and films have attracted global attention for their applications in near-infrared (NIR)-shielding windows. However, they are unstable in strong ultraviolet, humid heat, alkaline and/or oxidizing environments and are difficult to be coated on glass surfaces with complex shape. Here, we address these limitations by doping sodium tungsten bronze (Na_xWO₃) into bulk glasses using a simple glass melting method. X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, TEM and SEM-EDS characterization confirmed the presence of sodium tungsten bronze (Na_xWO₃) functional units inside the 34SiO₂-38B₂O₃-28NaF glass matrix. Because the functional units are well protected by the glass matrix, the fabricated glasses are stable under hot, humid, oxidizing conditions, as well as under ambient conditions, with no change after 360 days. The NIR-shielding performance of these glasses can be adjusted to as high as 100 % by varying WO_x concentration (2-8 mol%) and quenching temperature (1000-1400 °C). With a content of 6 mol% WO_x and a quenching temperature of 1000 °C, the bulk glass shows 63 % transmission of visible light and only 11 % transmission of NIR light at 1100 nm. Thermal insulation experiments show that the NIR-shielding performance of the glasses are far superior to commercial soda lime window glass or indium-doped tin oxide (ITO) glass, and comparable to cesium tungsten bronze coated glass. The novel bulk glasses have higher stability, simpler processing, and can be easily made into complex shapes, making them excellent alternative materials for energy-saving glasses.

Key words: Tungsten bronze, Tungsten oxide, Near infrared shielding, Energy-saving glass