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

Bulk and nanoparticles of n -type CuFeS 2 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-CuFeS 2. FE-SEM micrographs illustrate the cuboid morphology of nano-CuFeS 2 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 S2− present in CuFeS 2 are further confirmed by XPS studies. The weak ferromagnetic nature of both bulk and nano-CuFeS 2 with magnetic saturation of ∼0.075 emu/g and ∼0.036 emu/g, respectively, has been observed from VSM measurements. The bulk n -type CuFeS 2 exhibits the Seebeck coefficient of −160 μV/K at room temperature, increasing to −187 μV/K for nano-CuFeS 2. Interestingly, a huge reduction in total thermal conductivity of ∼0.69 W/mK is observed in nano-CuFeS 2 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-CuFeS 2. Mid-to-long wavelength phonon scattering from the increased grain boundaries and reduced grain sizes of nano-CuFeS 2 and their corresponding reduction in lattice thermal conductivity as a function of temperature. [Display omitted] • Bulk and nano CuFeS 2 samples have been successfully synthesized using vacuum melting and hydrothermal method, respectively. • The mean particle size of nano-CuFeS 2 was calculated to be ∼130 nm. • An increase in Seebeck co-efficient (S) of −305 μV/K at 623 K was observed for nano-CuFeS 2. • Ultra-low thermal conductivity of ∼0.69 W/mK at 623 K was observed for nano-CuFeS 2. • Overall, a maximum figure of merit (zT) of 0.28 at 623 K is achieved for nano-CuFeS 2. [ABSTRACT FROM AUTHOR]