Exploring the thermoelectric behavior of intrinsic and defect induced LaCoO3 with selected alkaline earth metals

Perovskite oxides of transition elements with multiple oxidation states have attracted widespread attention owing to the formation of inherent defects. In addition, when modified with suitable dopants these materials can exhibit remarkable properties. LaCoO3 and defect induced La0.8A0.2CoO3 (A- Mg, Ca, Sr, Ba) were synthesized by using sol-gel method. Scanning Electron Micrographs of sintered pellets of these compositions revealed distinct grain and grain boundaries with minimal porosity. Electrical studies indicated semiconductor to metal transition in all compositions after around 500 °C. Conductivity of the materials were significantly improved upon doping-from 0.063 S/cm for LCO to 1955.68 S/cm for LBCO at room temperature. Consequently thermoelectric studies also revealed higher power factor values at temperatures below 500 °C. The highest power factor was observed for LSCO of 1.02 x 10−4 W/mK2 at room temperature. An overall improvement in ZT was observed at room temperature due to doping in spite of increase in thermal conductivity. Fig.G1: Electron micrographs, electron transport and thermopower data of SLCO pellet (a) Scanning Electron Micrograph (inset shows the size distribution), (b) Transmission Electron Micrograph of crushed sample, (c) high resolution image showing the grain boundary, (d) carrier concentration (inset shows mobility), (e) Seebeck coefficient (inset shows power factor). [Display omitted] •LaCoO3 and defect induced La0.8A0.2CoO3 (A= Mg, Ca, Sr, Ba) were synthesized by using sol-gel method.•Electrical studies indicated the improvement in carrier concentration and mobility of the materials upon doping.•Doped compositions showed better thermopower at all temperature ranges.•Despite higher in thermal conductivity, La0.8Sr0.2CoO3 exhibited the highest figure of merit at room temperature.