The Electrical and Thermal Transport Properties of La-Doped SrTiO3 with Sc2O3 Composite

Abstract

Donor-doped strontium titanate (SrTiO3) is one of the most promising n-type oxide thermoelectric materials. Routine doping of La at Sr site can change the charge scattering mechanism, and meanwhile can significantly increase the power factor in the temperature range of 423–773 K. In addition, the introduction of Sc partially substitutes Sr, thus further increasing the electron concentration and optimizing the electrical transport properties. Moreover, the excess Sc in the form of Sc2O3 composite suppresses multifrequency phonon transport, leading to low thermal conductivity of κ = 3.78 W·m−1·K−1 at 773 K for sample Sr0.88La0.06Sc0.06TiO3 with the highest doping content. Thus, the thermoelectric performance of SrTiO3 can be significantly enhanced by synergistic optimization of electrical transport and thermal transport properties via cation doping and composite engineering.

Potential of La-Doped SrTiO3 Thin Films Grown by Metal–Organic Vapor Phase Epitaxy for Thermoelectric Applications

“…Semiconducting n-type doped SrTiO 3 has been achieved by the incorporation of different elements like Nb or Ta on the Ti site or Y, Sm, or La on the Sr site. A weakness of SrTiO 3 regarding its use in thermoelectric devices is the relatively low electrical conductivity, based on the high effective mass and the resulting low charge carrier mobility, and simultaneously high thermal conductivity κ (about 5–18 Wm –1 K –1 ), which is reasoned by the centrosymmetric cubic structure that offers low effective phonon scattering centers. This weakness can be mitigated, for instance, by manufacturing superlattice heterostructures (such as Si/Ge or PbTe/PbSe 0.20 Te 0.80 superlattices), which leads to a reduction of thermal conductivity, or by decoupling the thermal and electronic transport by a suitable choice of the film and substrate thermal conductivities and respective thicknesses …”