Thermoelectric (TE) materials are able to interconvert thermal and electric energy. To understand the promising Mg3Sb2-type TE materials produced in our lab, neutron diffraction data is necessary for us to fully examine and correlate the structure with their remarkable properties.The purpose of this proposal, therefore, is to explore the structure of Mg3Sb2-type TE materials (with Bi/Te) at ambient conditions and at high temperature using neutron diffraction. Furthermore, we will also examine and compare high temperature structure modifications when the sample is in powder and in dense pellet form. The need to pursue such a multi-faceted experimental regime is related to the applied nature of TE materials. Such materials have the potential to revolutionize the energy sector if we can optimize energy conversion efficiency, and generate dense products that are robust and reliable.