Search

Abstract Quaternary Mg 2 Si 0.25 Ge 0.05 Sn 0.7 based solid solutions were synthesized by B 2 O 3 flux method combined with spark plasma sintering (SPS) technique. The carrier concentration was tuned by adjustment of the SPS temperature. The electrical conductivity, Seebeck coefficient and thermal conductivity were measured in the temperature range from 320 to 820 K. The results show that the density, carrier concentration and lattice thermal conductivity monotonically increase with sintering temperature. With increasing carrier concentration the electron effective mass increases due to band convergence, while the electron mobility drops dramatically from 70.5 cm2 V−1 s−1 to 7.5 cm2 V−1 s−1. The phonon scattering mechanism in the quaternary solid solutions was analyzed using the Abeles model. The calculation shows that mass fluctuation scattering plays a crucial role in reducing the lattice thermal conductivity. Owing to band convergence combined with scattering of the phonons by point defects, a ZT max of 1.1 at 700 K was obtained for Mg 2 (Si 0.2 Ge 0.1 Sn 0.7) 0.99 Sb 0.01. Graphical abstract Band convergence combined with point defect scattering of phonons leads to a high ZT of 1.1 at 700 K in Mg 2 (Si 0.2 Ge 0.1 Sn 0.7) 0.99 Sb 0.01. fx1 Highlights • Mg 2 (Si,Ge,Sn) solid solutions have been successfully prepared by B 2 O 3 flux method. • Band convergence markedly enhances the Seebeck coefficient. • Mass fluctuation scattering effectively reduces the lattice thermal conductivity. • A ZT max of 1.1 at 700 K was obtained for Mg 2 (Si 0.2 Ge 0.1 Sn 0.7) 0.99 Sb 0.01. [ABSTRACT FROM AUTHOR]