Magnesium tin silicide based thermoelectrics contain earth abundant and non-toxic elements, and have the potential to replace established commercial thermoelectrics for energy conversion applications. In this work, porosity was used as a means to improve their thermoelectric properties.Compared to dense samples of Sb doped Mg 2 Si 0.5 Sn 0.5 with a maximum zT of 1.39 at 663 K, porous samples (37% porosity) prepared by a pressure-less Spark Plasma Sintering technique showed significantly lower thermal conductivity and higher Seebeck coefficient, resulting in an increased maximum zT of 1.63 at 615 K. The possible origins of the enhanced Seebeck coefficient can be attributed to change of carrier concentration and modification of the band structure, by microstructural engineering of the surface composition and particle-particle contacts

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