Relationship between thermoelectric properties and infrared emissivity of Gd-doped SrO(SrTiO3)2

Compared with perovskite SrTiO₃, SrO(SrTiO₃)₂ exhibits lower thermal conductivity, while maintaining a high Seebeck coefficient, making it a promising material for photothermoelectric conversion. However, the relationship between its infrared and thermoelectric properties remains unexplored. This study examines the effect of Gd doping on these properties of SrO(SrTiO₃)₂. Increased Gd doping induces a gradual transformation of SrO(SrTiO₃)₂-based into a SrTiO₃-based material, resulting in a composite comprising three phases and a notable reduction in thermal conductivity. At 973 K, the thermal conductivity decreases to a minimum of 1.4 W m⁻¹ K⁻¹, which is 23 % lower than undoped SrO(SrTiO₃)₂ and 51 % lower than SrTiO₃. Like SrTiO₃, SrO(SrTiO₃)₂ absorbs infrared radiation in the 8–14 μm range. Although the highest ZT value reaches only 0.06 at 973 K, it shows a positive correlation with infrared emissivity. These findings are valuable for advancing the application of thermoelectric effects and the development of high-performance infrared materials.