Li doped Mg2Si p-type thermoelectric material: Theoretical and experimental study

Abstract

The aim of the study was to determine the influence of Li dopant on transport properties of Mg2Si by using computational methods and experimental study.The results of theoretical studies of electronic structure (Full Potential Linearized Augmented Plane Wave Method), electron density topology and bonding properties (Bader’s Quantum Theory of Atoms in Molecules topological analysis of total electron density) in Li-doped Mg2Si are presented. Detailed analysis of calculated band structures and densities of states shows that for two cases analyzed i.e.: Li substituting Si or Li located in interstitial region (4b Wyckoff position), the addition of lithium impurity leads to n-type conduction. On the other hand, if Li is located in Mg position, the samples have p-type conduction.A series of samples with the nominal compositions of Mg2−xLixSi, (x=0–0.3) were prepared using the Pulsed Electric Current Sintering Technique (PECS) method. Structural and phase composition analyses were carried out by X-ray diffraction. The investigations of the influence of Li dopant on the transport properties i.e.: electrical conductivity, the Seebeck coefficient and the thermal conductivity were carried out. Carrier concentration was measured using the Hall method. The positive value of the Seebeck coefficient indicates that all examined samples show p-type conductivity, which is consistent with the theoretical predictions.