The electronic-thermal transport properties and the exploration of magneto-thermoelectric properties and the Nernst thermopower of Ag2(1+x)Se

Abstract

Room temperature synthesis is beneficial for compositional homogeneity and controlled synthesis of Ag2Se, which was used for preparing Ag2(1+x)Se samples in this study. The increase of Ag content remarkably increased electron density of Ag2(1+x)Se, leading to a notable increase in electrical conductivity and thermal conductivity as well as an obvious decrease in the Seebeck coefficient. The Ag-deficient Ag2(1+x)Se samples had superior dimensionless figure of merit ZT among all samples, resulting from their relatively larger power factor and smaller thermal conductivity. Ag1.98Se possessed the highest ZT value of 0.68@373 ​K among all samples, which was obviously lower than previous reports due to its inferior Seebeck coefficient and power factor. Under magnetic fields, the ZT values of Ag2(1+x)Se were slightly reduced due to increased electrical resistivity, while their Nernst thermopower (~15 ​μVK−1@300 ​K and 5 ​T) were very small because of relatively high electron density and not high enough carrier mobility. This research pointed out that, the ZT values and Nernst ZT values of Ag2Se could be significantly improved through optimizing their composition and microstructure for lower electron density, higher carrier mobility and larger Seebeck coefficient.