Improving Thermoelectric Performance of AgSbTe2 through Suppression of Ag2Te and Band Convergence via Mg and Ti Codoping.

ABSTRACT

In this study, the impact of codoping Mg and Ti on the thermoelectric performance of AgSbTe2 materials was investigated. Through a two-step synthesis process involving slow cooling and spark plasma sintering, AgSb0.98-xMg0.02TixTe2 samples were prepared. The introduction of Mg and Ti dopants effectively suppressed the formation of the undesirable Ag2Te phase. Density functional theory (DFT) calculations confirmed that Ti doping facilitated the band convergence, leading to a reduction in the effective mass of the carriers. This optimization enhanced carrier mobility and, consequently, electrical conductivity. Additionally, the codoping strategy resulted in the reinforcement of point defects, which contributed to a decrease in lattice thermal conductivity. The AgSb0.98-xMg0.02TixTe2 sample achieved a maximum figure of merit (ZT) value of 1.45 at 523 K, representing an 87% improvement over the undoped AgSbTe2 sample. The average ZT value over the temperature range of 323-573 K was 1.09, marking a significant enhancement in thermoelectric performance. This research demonstrates the potential of Mg and Ti codoping as a strategy to improve the thermoelectric properties of AgSbTe2-based materials.