Effect of Ga-substitution for Fe sites of delafossite CuFe1-xGaxO2 (X = 0.0, 0.1, 0.3, 0.5) on thermal conductivity

Abstract

This work aimed to study the effect of the Ga3+-substitution of Fe3+ sites in CuFeO2 delafossite on its thermal conductivity. CuFe1-xGaxO2 (x = 0, 0.1, 0.3, and 0.5) samples were synthesized and their phase structure and ionic composition were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The thermal conductivity of the samples was measured at a high temperature range of 298-573 K. The XRD results confirmed that the samples were pure phase delafossite with hexagonal structure space group: R3m while the EDX results showed composition atomic percent of Ga 100% of x = 0.1, 93% of x = 0.3 and 90% of x = 0.5 and the XPS results revealed Cu1+ and Cu2+, Fe2+ and Fe3+, and Ga3+ ion states in the structure. The Ga-substitution decreased the thermal conductivity of the samples below that of nondoped CuFeO2. The high substitution sample (x = 0.5) exhibited the lowest thermal conductivity, 2.5 W/mK at 573 K. Ga substitution into Fe sites affected the lattice thermal conductivity partly through phonon scattering processes arising from mass difference and lattice strain.