Spin-orbital entropy driven enhanced thermopower in Bi doped La0.95Sr0.05CoO3 strongly correlated perovskite

Abstract

In this work, we have measured the thermopower and resistivity of polycrystalline pure and Bi doped La0.95Sr0.05CoO3 in the temperature of 303–753 K. The Bi doped sample shows an increased electrical resistivity of 3.30 Ωcm and a positive thermopower of 442 μVK−1 due to the increased crystal field splitting energy and stabilization of LS Co3+ ions. The calculated weighted mobility μW of 2.24 to 2.74 cm2V−1s−1 and weighted carrier concentration nW of 8.44 × 1017 to 3.87 × 1020 cm−3 align well with the increased electrical resistivity. Apart from the carrier contribution to the thermopower αp, the increased spin-orbital entropy contribution αSO= 154 μVK−1 from the spin state fluctuation leads to the anomalous enhancement in thermopower of Bi doped La0.95Sr0.05CoO3. The obtained results indicate that the spin-orbital entropy is a key parameter in driving the thermoelectric properties of strongly correlated oxides.