Thermoelectric properties of high-entropy rare-earth cobaltates

High-entropy concept introduced with a promising paradigm to obtain exotic physical properties has motivated us to explore the thermoelectric properties of Sr-substituted high-entropy rare-earth cobaltates i.e.,(LaNdPrSmEu)_(1-x)Sr_(x)CoO_(3)(0≤x≤0.10).The structural analysis of the samples,synthesized using the standard solid-state route,confirms the orthorhombic structure with the Pbnm space group.The Seebeck coefficient and electrical resistivity decrease with rising Sr concentration as well as with an increase in temperature.The multiple A-site ions in high-entropy rare-earth cobaltates result in an improved Seebeck coefficient(α)compared to La_(0.95)Sr_(0.05)CoO_(3),associated with a decrease in the Cosingle bondOsingle bondCo bond angle,which further enhances the power factor.The random distribution of cations at the rare-earth site results in a significant lowering of phonon thermal conductivity.As a result,a maximum figure of merit(zT)of 0.23 is obtained at 350K for(LaNdPrSmEu)_(0.95)Sr_(0.05)CoO_(3),which is one of the highest values of zT reported at this temperature for oxide materials.This study shows promise to decouple thermoelectric parameters using the high-entropy concept in several materials.