Suppression of intrinsic thermal conductivity in Sr(1−x)Gd(x)TiO(3) ceramics via phonon-point defect scattering for enhanced thermoelectric application

A substantial reduction in the thermal conductivity for strontium titanate (ABO(3)) perovskite structure was realized for the A-site substitution of gadolinium (rare earth element) in SrTiO(3) ceramics. The effect of Gd(3+) substitution on the structure, composition, and thermoelectric properties of SrTiO(3) was investigated. The substitution of Gd(3+) in the SrTiO(3) 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(−1) K(−1) for the minimal substitutional composition (Sr(0.99)Gd(0.01)TiO(3)) which is 30% less than that of SrTiO(3) at 303 K. The variation in the ionic radii and atomic mass of the heavier rare earth Gd(3+) substituted over Sr(2+) 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.