Structural, microstructural, magnetic, and thermoelectric properties of bulk and nanostructured n-type CuFeS2 Chalcopyrite

Bulk and nanoparticles of n-type CuFeS2 Chalcopyrite have been synthesized using vacuum melting reaction and conventional hydrothermal method, respectively. The powder XRD pattern of both the samples has confirmed phase formation, and the crystallite size was calculated to be-30 nm for nano-CuFeS2. FE-SEM micrographs illustrate the cuboid morphology of nano-CuFeS2 with particles sizes in the range of 50-200 nm, and EDS analysis confirms the nominal composition. The elemental composition and electronic states of Cu1+, Fe3+, and S-2-present in CuFeS2 are further confirmed by XPS studies. The weak ferromagnetic nature of both bulk and nano-CuFeS2 with magnetic saturation of-0.075 emu/g and-0.036 emu/g, respectively, has been observed from VSM measurements. The bulk n-type CuFeS2 exhibits the Seebeck coefficient of-160 mu V/K at room temperature, increasing to-187 mu V/K for nano-CuFeS2. Interestingly, a huge reduction in total thermal conductivity of-0.69 W/mK is observed in nano-CuFeS2 compared to the bulk sample (-4.18 W/mK) at room temperature, resulting in an overall enhanced thermoelectric figure of merit, zT of-0.28 at 623 K for nano-CuFeS2.