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

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) (Sr0.5Ba0.3La0.2)1−xPbxNb2O6−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 (κlat) 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.