SYNTHESIS AND CHARACTERIZATION OF THERMOELECTRIC MATERIALS FOR EFFICIENT HARNESSING OF SOLAR ENERGY

Abstract

Thermoelectric generators (TEGs), based on the Seebeck effect, which converts heat into useful electrical energy, are gaining momentum for renewable energy applications. However, it is well accepted that for the thermoelectric technology to compete with other recognized green-energy generation technologies, like photovoltaics, the material, and manufacturing costs of thermoelectric devices, have to be significantly reduced. Also, the majority of the presently available competent thermoelectric materials possess expensive constituent materials (Te, Ge, Ag, rareearths, etc.), which adds another dimension to this problem. Thus, the thrust of thermoelectric research for energy generation is currently focussed on the development of n and p-type materials, which are thermoelectrically compatible, thermally stable and consisting of elements that are earth-abundant and non-toxic. Mg2Si (n-type) and MnSi1.73 (p-type) are the ideal combinations for developing a cost-effective and nontoxic thermoelectric device due to their Seebeck coefficient compatibility, thermal and chemical stability and low density. The present work is an emphasis on the synthesis and characterization of two such thermoelectric compounds, n-type Mg2Si, and p-type MnSi1.73, as cost-effective thermoelectric technology, which is anticipated to play a vital role in meeting the energy challenge of the future. This present work reports the synthesis of Mg2Si and MnSi1.73 using reactive spark plasma assisted sintering process, which consumes only a limited processing time as compared to long duration hours using conventional manufacturing techniques. The phase crystal structure, chemical composition, and microstructure of synthesized materials were studied employing X-ray diffraction, highresolution electron microscopy, and energy dispersive spectroscopy techniques. The electrical conductivity, thermal conductivity and Seebeck coefficient of synthesized Mg2Si and MnSi1.73 have been studied, to understand its thermal-electric conversion efficiency. The mechanical performance of synthesized materials is also crucial to circumvent the unexpected structural failure of their components during actual operational conditions. The comprehensive spectrum of mechanical properties of synthesized Mg2Si and MnSi1.73 has been studied, to recognize the durability of these thermoelectric materials, under actual working environmental conditions.