Pressure induced convergence of conduction bands in Al doped Mg2Si: Experiment and theory

High-pressure and high-temperature (HPHT) synthesis provides an effective way to tune the band structure of materials and improve their electronic properties. To investigate the influence of synthesis pressure on electronic properties, Mg1.97Al0.03Si samples were synthesized using the HPHT method. The maximum effective mass 0.92me is obtained for the sample prepared with the synthesis pressure of 3 GPa, leading to the biggest Seebeck coefficient −201.3 μV/K at room temperature. Meanwhile, the 3 GPa sample obtains the higher electron carrier concentration and electrical conductivity, resulting in nearly overall enhancement of power factor. The Density Functional Theory (DFT) calculations evidences that the Conduction Bands Minimum (CBM) can be tuned effectively by applied pressure and the convergence of the CBM leads to a larger effective mass of DOS, which are beneficial to the enhancement of power factors. These results indicate that high-pressure is a powerful tool to tune Mg1.97Al0.03Si band structures.