Solar control on irradiated Ta₂O₅ thin film

Ta₂O₅ thin films were prepared by sol-gel prosses on Corning 2947 glass substrates to obtain good quality films. These films were placed around the source and exposed to gamma radiation at 0.35, 2.58 and 4.5 kGy absorbed dose at room temperature using Co-60 radioisotope. Ta ₂O₅ coated thin films were irradiated with beta radiation at 0.13 kGy using Sr-90 radioisotope. It is suggested that the mechanism of absorption is related to an allowed indirect transition at Ta₂O ₅ film. When the absorbed dose of Ta₂O₅ films increased from 0.35 kGy to 4.5 kGy the optical band gaps of Ta₂O ₅ films decreased from 2.40 eV to 1.63 eV 24 hours later from the irradiation proces using Co-60 radioisotope. But, the optical band gap of irradiated Ta₂O₅ film increased again 44 months later from the irradiation proces. The optical band gaps of irradiated Ta ₂O₅ film at 0.35 kGy and 4.5 kGy are detected as 2.43 eV to 1.75 eV. The effect of gamma irradiation on the solar properties of Ta ₂O₅ films is compared with that of beta irradiation. Using the optical properties, the redistribution of the absorbed component of the solar radiation and the shading coefficient (sc) are calculated as a function of the convective heat-transfer coefficient in order to achieve the control of solar energy. When the absorbed dose increased the shading coefficient decreased considerably. Changes in shading coefficient of irradiated Ta₂O ₅ films are performed 24 hours later and 44 months later from the irradiation process in order to determine post irradiation behavior of Ta ₂O₅ films. Shading coefficient of irradiated Ta ₂O₅ films increased manifestly 44 months later from the irradiaiton. The shading coefficient of the irradiated Ta₂O ₅ films with Sr-90 radioisotope differ significantly from irradiated Ta₂O₅ film with Co-60 radioisotope. Beta irradiation is more effective than gamma irradiation on the change of shading coefficient of Ta₂O₅ films.