| Abstract Scope |
Although oxides showed lot of promises as thermoelectric materials, their figure-of-merit, ZT is low primarily because of high lattice thermal conductivity (k_l). Researchers found it challenging to reduce k_l of perovskites possessing low phonon mean-free-path (Lphonon). Recently, we put forward a strategy of achieving ultra-low k_l in high entropy perovskite (HEP) by populating 5 transition metals in the B-site to induce more anharmonicity causing enhanced multi-phonon scattering. Sr(TiFeNbMoCr)O3 HEP showed the lowest Lphonon among all the SrTiO3 based materials reported in the literature resulting in ultralow thermal conductivity ~0.7 W/mK. In-depth analysis of phonon transport mechanism in HEP performed by using Debye-Callaway model in correlation with Microstructural and elemental analysis suggests that presence of 5 cations in B-site causes enhanced anharmonicity leading to higher order phonon scattering. Further, we demonstrated synergistic combination of large Seebeck and record low thermal conductivity in novel high entropy niobate (Sr0.2Ba0.2Li0.2K0.2Na0.2)Nb2O6, with tungsten bronze structure. |