Magnesium silicide (Mg2Si) is the one of the most attractive and promising green thermo-electric material to convert the heat into electricity in the mid temperature range (RT to 600 degrees C). However, synthesizing of Mg2Si compound through liquid and solid state processing carries several challenges such as processing time, inhomogenous stoichiometry and phase purity. The alternative method is demonstrated by rapid in-situ synthesis of pure nano-crystalline Mg2Si doped with Bi (0-0.025 at.%) by spark plasma sintering (SPS). XRD and electron microscopy studies confirm the formation of Mg2Si compound and EDS confirm chemical and doping homogeneity. The superior power factor of 11 mu W/cm-k(2) is achieved at 550 degrees C. (C) 2017 Elsevier B.V. All rights reserved.