Inducing oxide ion vacancies in Sr2CoSbO6 as a strategy to decouple power factor and thermal conductivity

Abstract

In this correspondence, we demonstrate the effect of substituting a d⁰ metal ion like Ti⁴⁺ in the place of a d¹⁰ metal ion like Sb⁵⁺ in Sr₂CoSbO₆ double perovskite on its thermoelectric properties. Ti substitution led to an enormous decrease in resistivity from a value of 15.59 Ω cm to 0.17 Ω cm, which resulted in an increment of 16 times in the power factor. Also the doping resulted in considerably lowering the thermal conductivity by half the value of the parent compound. The reason is attributed to the induction of oxide ion vacancies in the crystal structure, which acted both as an electron sink and a phonon scatterer. Such a trend in a material is essential for exhibiting a high dimensionless figure of merit value and can be applied in related oxide compounds tolerating oxide ion vacancies.