Entropy-mediated Pb doping in tungsten bronze (Sr0.5Ba0.3La0.2)1−xPbxNb2O6−δ oxides for synergistic electron–phonon transport optimization

Abstract

Oxide thermoelectric materials demonstrate superior structural stability and environmental compatibility; however, their practical applications are limited by relatively low figure-of-merit (ZT) values. This study overcomes this limitation in strontium barium niobate (SBN) through entropy-mediated Pb doping, achieving a record ZT of 0.42 at 1073 K – the highest reported for SBN-based ceramics. By designing a medium-entropy (ΔS = 1.30R) (Sr_0.5Ba_0.3La_0.2)_1−xPb_xNb₂O_6−δ system, electron–phonon transport properties are effectively optimized. Pb doping enhances carrier concentration while maintaining a high Seebeck coefficient, attributed to the contribution of Pb orbitals. Simultaneously, lattice thermal conductivity (κ_lat) is reduced through dislocation engineering and induced strain fields, as verified by geometric phase analysis. The performance improvement is further supported by local distortions of NbO₆ octahedra, as well as the formation of lead and oxygen vacancies. This work not only demonstrates the potential of SBN as a promising oxide thermoelectric material but also presents a broadly applicable doping strategy for developing high-performance oxide energy conversion materials.