Enhancement of thermoelectric performance of Bi0.5Sb1.5Te3 alloy by inclusion of LaVO3 Mott insulator

The enhancement of thermoelectric (TE) figure of merit, ZT, is of great essence to improve the efficiency of TE devices since the commercial applications of TE devices have been constrained due to low performance. Here, we report a novel approach for ZT improvement via a synergistic effect of unusual conducting behavior and energy filtering at the (LaVO3)/Cu0.07Bi0.5Sb1.5Te3 incoherent interfaces. In this work, the incoherent interfaces have been engendered by the incorporation of LaVO3 (LVO) nanoparticles into Cu0.07Bi0.5Sb1.5Te3 (BST) matrix, inducing a remarkable enhancement in electrical conductivity due to defect formations and an insulator-to-metal transition. This induced conducting behavior also eminently suppressed the adverse intrinsic excitation thanks to increases in hole density and band turning in composites. Meanwhile, the low-work function in the BST matrix establishes an interface potential with a height of 2.03 eV that efficiently filters low energy carriers, and consequently alleviates the decrement of Seebeck coefficients. Upon LVO addition, not only does the bipolar thermal conductivity decrease but the lattice thermal conductivity approaches the amorphous limit due to enhanced phonon scattering mechanisms at incoherent interfaces. A significant thermoelectric figure of merit, ZT of 1.26 and ZT(avg) = 1.13 are achieved for the sample with 5 wt% of LVO in BST, which is about 26% and 20% higher than the pristine BST, respectively, thanks to its optimized power factor and low thermal conductivity. Additionally, LVO dispersion strengthens the mechanical properties of the composites, demonstrated in their enhanced hardness and compressive strength.