IMF2017

n-type thermoelectric material with good Figure of Merit (ZT = S²σT/k) is need of the hour to design a thermoelectric power generator which consists of p-type and n-type TE module connected electrically in series and thermally in parallel configuration. In this investigation we report high temperature thermoelectric properties of SrTi_0.85Nb_0.15O₃ (STN) and Graphene Oxide (GO) nanocomposites prepared via Spark Plasma Sintering (SPS). The oxidation state of Ti and Nb in these ceramics were studied by XPS. Rietveld refinement of these oxides defined them as cubic crystal with Pm-3m space group. TEM study confirmed the existence of GO in the grains as well as in the grain boundaries of these nano composites. The temperature dependent electrical conductivity of pure STN exhibits semiconducting nature (dσ/dT > 0) from room temperature to 1223 K. Addition of little amount of GO in the matrix causes increase in the electrical conductivity however, with further increase in wt% GO, electrical conductivity changes in the order of 10² with metal like behaviour (dσ/dT < 0), without major change in Seebeck coefficient (ranges between -80 µV to -180 µV) and resulted maximum power factor of 1300 µW/mK² for 1.5 wt% GO. The Seebeck coefficient was negative throughout the temperature range of measurement, indicating n-type behaviour. The thermal conductivity was measured to calculate the ZT value of these nano composites and maximum ZT of more than 1 was observed. Further the conduction mechanism in the composites were discussed by Variable Range Hopping and Small Polaron hopping mechanisms.