Chemical Reduction of Nd_1.85Ce_0.15CuO_4−δPowders in Supercritical Sodium Ammonia Solutions

Abstract

Nd 1.85 Ce 0.15 CuO 4− powders are chemically reduced in supercritical sodium ammonia solutions from room temperature to 350 ∘ C. The crystallographic structure of the reduced powders is investigated from Rietveld refinement of X-ray powder diffraction. The atomic positions are maintained constant within experimental errors while temperature factors of all atoms increase significantly after the chemical treatments, especially of Nd/Ce atoms. The ammonothermally reduced Nd 1.85 Ce 0.15 CuO 4− powders show diamagnetic below 24 K which is contributed to the lower oxygen content and higher temperature factors of atoms in the treated compound. The ammonothermal method paves a new way to reduce oxides in supercritical solutions near room temperature.