The electronic structure of the CuRh1−xMgxO2 thermoelectric materials: An X-ray photoelectron spectroscopy study

A detailed X-ray photoelectron spectroscopy study has been performed for the CuRh1−xMgxO2 (x=0, 0.04 and 0.10) series for a better understanding of the role of the Mg2+ substitution on the electrical properties and the value of the Seebeck coefficient. This study is based on an analysis of different compounds such as Rh2O3, Sr2RhO4 and CuCrO2 in order to characterize different oxidation states (Rh3+ and Rh4+ in octahedral oxygen environment and Cu+ in a dumbbell O–Cu–O coordination). The Cu2p signal of copper in the non-doped compounds CuCrO2 and CuRhO2 reveals different electronic structures. An evolution of the Cu2p core signal with the increase of Mg2+ content in the CuRh1−xMgxO2 is highlighted by XPS. The differences observed, especially for the Cu2p core peaks are discussed for the non-doped compounds CuCrO2 and CuRhO2 as for the CuRh1−xMgxO2 series upon Mg2+ substitution.