Phonon-glass electron-crystal behaviour by A site disorder in n-type thermoelectric oxides

Abstract

Phonon-glass electron-crystal (PGEC) behaviour is realised in La_0.5Na_0.5Ti_1−xNb_xO₃ thermoelectric oxides. The vibrational disorder imposed by the presence of both La³⁺ and Na⁺ cations on the A site of the ABO₃ perovskite oxide La_0.5Na_0.5TiO₃ produces a phonon-glass with a thermal conductivity, κ, 80% lower than that of SrTiO₃ at room temperature. Unlike other state-of-the-art thermoelectric oxides, where there is strong coupling of κ to the electronic power factor, the electronic transport of these materials can be optimised independently of the thermal transport through cation substitution at the octahedral B site. The low κ of the phonon-glass parent is retained across the La_0.5Na_0.5Ti_1−xNb_xO₃ series without disrupting the electronic conductivity, affording PGEC behaviour in oxides.