Effects of spin entropy and lattice strain from mixed-trivalent Fe3+/Cr3+ on the electronic, thermoelectric and optical properties of delafossite CuFe1−x Cr x O2 (x = 0.25, 0.5, 0.75)

摘要: Mixed-trivalent Fe3+/Cr3+ content CuFe1−x Cr x O2 (x = 0.25, 0.5, and 0.75) compounds were synthesized to investigate the effects of spin entropy, lattice strain on their electronic, thermoelectric optical properties. The XPS results showed existence mixed Cu1+/Cu2+, Fe3+/Fe4+ Cr2+/Cr3+ ion states in structures. Fe3+/Cr3+ions caused a strong correlation occur between orbitals carriers octahedral layer sample, affecting carrier degeneracy Seebeck coefficient behaviour, Cu2+ Fe4+ ions an effect enhancing electric conductivity. These meant that CuFe0.75Cr0.25O2 had highest electrical conductivity, enhanced compared CuFeO2-based compounds, thermopower value. lowest thermal conductivity was CuFe0.5Cr0.5O2, which result mismatched atomic radii trivalent Fe3+(0.645 A)/Cr3+(0.615 A), structure thus affected point defect scattering phonon total because it maximum strain. Overall, elements have value dimensionless figure merit ZT, with four times six CuCrO2-based compounds. With regard properties, causes indirect gap increase increasing content, but has no direct gap. verified mixed-trivalent properties by causing entropy occur.