Oxide Thermoelectrics: The Role of Crystal Structure on Thermopower in Strongly Correlated Spinels

This dissertation reports on the synthesis, structural and thermal characterization and electrical and thermal transport properties of a variety of strongly correlated spinels. General structure property relationships for electrical and thermal transport are discussed. However, the relationship between thermopower and features of the crystal structure such as spin, crystal field, anti-site disorder, and structural distortions are explored in depth. The experimental findings are reported in the context of improving existing oxide thermoelectric materials, screening for new materials or using thermopower as a unique characterization tool to determine the cation distribution in spinels. The need for improved n-type oxide thermoelectric materials has led researchers to consider mixed valence (+3/+4) manganese oxides. Contrary to previous findings we report herein that the LiMn2O4 compound reaches the relatively large n-type thermopower of -73 μV/K which is three times larger than the value observed in other