Effect of Sr doping and temperature on the optical properties of BaTiO3

Ceramics with low solar absorptivity and high infrared emissivity play an important role in radiative cooling applications. BaTiO 3 , for instance, is one promising radiative cooling ceramic, although it has been mainly explored only in electronics. In this work, the solar-reflective and infrared-radiative properties of Sr-doped BaTiO 3 are studied systematically. Ba 1- x Sr x TiO 3 ( x  = 0, 0.2, 0.25, 0.3, 0.35) ceramics synthesized by sol-gel method were investigated in terms of their microstructure, phase transition, and optical properties . Increasing infrared emissivity and solar absorptivity were observed with increasing Sr content. The optimized Ba 1- x Sr x TiO 3 achieves solar absorptivity of 0.17 and infrared emissivity of 0.78. The lowest absorptivity-emissivity ratio of 0.24 was observed for Ba 0.8 Sr 0.2 TiO 3 . Meanwhile, the solar absorptivity and infrared emissivity exhibited temperature stabilization, even affront heat-induced phase transition. Finally, the coupling relation between band gap, Ti–O vibration, and optical properties of Ba 1- x Sr x TiO 3 ceramics are clarified, which is promising to improve their radiative cooling performance.