Synthesis and Development of Thermoelectric Properties in Layered Bi2A2CoO6

Abstract

Bi-based layered cobalt oxide [Bi2 A 2CoO6] with A = (Ca2+, Mg2+) nanoparticles were prepared by co-precipitation method. Coprecipitation method was used to improve homogeneity and phase purity of nanoparticles and is rarely reported for such type of materials. From X-ray diffraction (XRD) data, structural analysis was carried out for both samples Bi2Ca2CoO6 (BCCO) and Bi2Mg2CoO6 (BMCO). Crystallite size, lattice constants, and volume of unit cell were calculated using XRD data. Both compositions showed monoclinic crystal structure with space group C2/c. Crystallite sizes obtained were 52 and 50 nm for BCCO and BMCO samples, respectively. Scanning electron micrographs show the particle-like morphology with an average particle size of 54 and 68 nm for BCCO and BMCO samples, respectively. Thermogravimetric analysis-(TGA)-differential scanning calorimetery (DSC) technique was used to observe role of heat changes in both the samples with temperature variation up to 1000∘C. BCCO was found thermally more stable as compared to BMCO. Electrical resistivity decreased with increase in temperature, and BMCO showed high values as compared to BCCO. Thermal transport properties like thermal conductivity, thermal diffusivity, and volumetric heat capacity were determined. Both compositions are low thermally conducting materials. BCCO sample showed higher thermal conduction as compared to BMCO. BCCO sample could be a better candidate as thermoelectric material as compared to BMCO.