Crystal structure and functional properties of Nd1.6Ca0.4Ni1-yCuyO4+δ as prospective cathode materials for intermediate temperature solid oxide fuel cells

Complex oxides Nd_1.6Ca_0.4Ni_1-yCu_yO_4+δ (y = 0.0–0.4) have been prepared by a pyrolysis of glycerol-nitrate compositions. According to the X-ray diffraction analysis, the materials are single-phase up to y = 0.3 and crystallize in an orthorhombic structure (Bmab) at room temperature. High-temperature studies assert that they all undergo a phase transition from orthorhombic to tetragonal (I4/mmm) structure in a range of 300–400 °C. With Cu doping, the over-stoichiometric oxygen content δ decreases from 0.07 (y = 0.0) down to 0.00 (y = 0.3). The studies on the compact samples reveal the maximum value of total conductivity (165 S cm^?1 at 420 °C) and the minimum value of the linear coefficient of thermal expansion (11.9·10^?6 K^?1 in a range of 400–1000 °C in air) at y = 0.2. Chemical compatibility of the Nd_1.6Cа_0.4Ni_1-yCu_yO_4+δ (y = 0.0, 0.2) oxides with oxygen- and proton conducting electrolytes (Ce_0.9Gd_0.1O_1.95, Ce_0.8Sm_0.2O_1.9 and BaCe_0.5Zr_0.3Y_0.1Yb_0.1O_3-δ) up to a temperature of 1100 °C is demonstrated.