Thermo and photochromic properties of Na2O–WO3–SbPO4 glasses

Tungsten phosphoantimoniate-based glasses containing sodium oxide were prepared and their thermochromic and photochromic properties investigated. Thermochromism is achieved by annealing glass samples at a temperature above glass transition (Tg). The phenomenon is characterized by an absorption band in the visible range and is non-reversible. These glasses also present photochromic properties when exposed to a laser beam (λ = 457 nm) and this effect is characterized by a large absorption band extending from the near infrared to the visible range. Photochromism is reversible by heat treatment at 150 °C. The properties of these glasses, as well as colour changes were studied using differential scanning calorimetry, infrared, Raman, UV–vis and M-Lines spectroscopies, and X-ray diffraction.