Oxygen reduction effect on T’-Pr_2-xCe_xCuO₄ nanopowders in the underdoped regime studied by X-ray absorption near edge structure

This research is aimed to examine oxidation state of Copper (Cu) in both as-synthesized and reduced T’-Pr_2-xCe_xCuO₄ (T’-PCCO) with x = 0, 0.10, and 0.15 using Cu K-edge x-ray absorption near edge structure (XANES). The T‘-PCCO nanopowders were successfully synthesized by the chemically dissolved method with HNO₃ as a dissolving agent continued by calcination at 1000° C for 15 h. The reduced T’-PCCO nanopowders were obtained by reduction annealing process at 700°C for 5 h under Ar gas atmosphere. The analyses of XANES spectra show that oxidation states of the Cu ions in all of the T’-PCCO nanopowders have values between +1 and +2. This indicates the existence of electron doping in the CuO₂ planes, even in the undoped T’-structure. It is found that the oxidation states of the Cu ions change after reduction annealing depending on the existence of apical oxygen in the T’-structure. Based on the XANES analyses, it is revealed that the change of oxidation state is influenced by the presence of both electron and hole carriers in the two-carrier model of T’-structure.