Post heat-treatment effects on CaMnO3 thermoelectrics grown by laser floating zone method

Abstract

Oxide-based thermoelectric materials are receiving a particular interest due to enhanced thermal and redox stability at high temperature, together with the absence of toxicity, and natural abundance of the constituent compounds. The objective of this work is to improve the thermoelectric performance of manganite-based oxide thermoelectrics processed by laser floating zone (LFZ) method through posterior heat treatment. Known Nb- and La-substituted CaMnO3-based materials, possessing promising thermoelectric properties, were selected as a model system. Detailed structural (XRD) and microstructural (SEM/EDS) studies were performed for the as-grown samples and those after posterior heat treatment. The results on electrical conductivity, Seebeck coefficient and thermal conductivity indicate that the thermoelectric performance is improved by this post-processing. Relevant effects of the thermal treatment on the fibre´s properties are discussed, suggesting that careful optimization of the laser and heat treatment conditions is necessary, when seeking high thermoelectric performance in oxides prepared by LFZ processing.