ICT2014 Abstracts

We report the enhancement in thermoelectric figure-of-merit (ZT) of Cu_1.98Se alloy synthesized by nanostructuring approach employing ball milling of the constituent elemental powders followed by their Spark Plasma Sintering (SPS). The nanostructure Cu_1.98Se sample exhibited an enhanced ZT which was ~ 25% higher than its bulk counterpart. The average crystallite size of the high energy ball milled Cu_1.98Se nanopowders and SPS samples was found to be ~10 nm and ~16 nm respectively, which suggests that fine nanoscale features introduced during ball-milling are retained post-sintering. The role of SPS, employed for consolidation sintering of nanopowders is substantially enhancing the ZT by reducing lattice thermal conductivity, has been highlighted. High Resolution Transmission Electron Microscopy (HRTEM) of both the bulk and nanostructured Cu_1.98Se samples have been investigated in terms of their crystalline size, lattice strain and other defects in order to correlate the observed reduction in lattice thermal conductivity due to these nanoscale features. The substantial enhancement in ZT primarily originates from significant reduction in thermal conductivity on nanostructuring, owing to enhanced scattering of phonons by high density nanoscale grain boundaries, microstructural point defects, and nanoscale residual porosity in the sintered nanostructured Cu_1.98Se sample.