Suppression of intrinsic thermal conductivity in Sr Gd TiO ceramics phonon-point defect scattering for enhanced thermoelectric application.

A substantial reduction in the thermal conductivity for strontium titanate (ABO) perovskite structure was realized for the A-site substitution of gadolinium (rare earth element) in SrTiO ceramics. The effect of Gd substitution on the structure, composition, and thermoelectric properties of SrTiO was investigated. The substitution of Gd in the SrTiO matrix resulted in the minimalization of thermal conductivity. The thermal conductivity followed a similar trend as that of thermal diffusivity, but specific heat capacity exhibited a non-monotonic trend. The thermal conductivity is reduced to 1.05 W m K for the minimal substitutional composition (SrGdTiO) which is 30% less than that of SrTiO at 303 K. The variation in the ionic radii and atomic mass of the heavier rare earth Gd substituted over Sr resulted in the reduction of thermal conductivity of SGTO ceramics caused by the corresponding boundary scattering at low temperatures and temperature-independent phonon-impurity scattering at high temperatures.