Crystal and defect structure of Nd1.9Ce0.1CuO4 +/- y

The crystal and defect structure of neodymium cerium cuprate (Nd1.9Ce0.1CuO 4+/-y) has been studied as a function of temperature (1200-1500 K) and oxyg en pressure (10(0)-10(-3) atm) via X-ray diffractometry, powder neutron dif fraction, and thermogravimetry methods. The oxygen nonstoichiometry changes from oxygen-excess (positive y values) to oxygen-deficient oxides (negativ e y values), The absolute values of oxygen nonstoichiometry y are calculate d from the neutron diffraction and thermogravimetry data. The materials ado pt the tetragonal structure (space group I4/mmm). A defect model is propose d for Nd2-xCexCuO4+/-y. It is concluded that oxygen vacancies V-O(..) (whic h occupy O(1) crystallographic positions (in planes)) and interstitial oxyg en O-i" (which occupy O(3) "apical" positions) are present simultaneously. Gaseous oxygen intercalates into the Nd1.9Ce0.1CuO4+/-y crystals and replac es oxygen vacancies in the O(1) position and interstitial oxygen atoms in t he O(3) positions. The theoretical model and the experimental data are in g ood agreement with each other, and the equilibrium constants of defect form ation have been calculated.