Structural, thermomechanical and electrical properties of new (1-x) Ce0.8Nd0.2O2-delta-xBaCe(0.8)Nd(0.2)O(3-delta) composites

Abstract

In this work composite (1-x)Ce0.8Nd0.2O2-delta-xBaCe(0.8)Nd(0.2)O(3-delta) ceramics were prepared via the one-step citrate-nitrate combustion procedure, and characterised by TG-DSC, XRD analysis, and SEM. Their transport properties were investigated across various temperatures (600-900 degrees C) and oxygen partial pressures (10(-23)-0.21 atm). The XRD data reveals an occurrence of single-phase oxides at x = 0, 1 and two phases with perovskite and fluorite structure at x = 0.25, 0.5, 0.75 in powders calcined at 1100 degrees C. Dense ceramic samples (93-95%) were sintered in air at 1500 degrees C for 3 h. The concentration dependence of the mean grain size is characterized by local minimum at x 0.5, while that of total conductivity exhibited a similar behavior; its minimal value was registered in the sample with the most extended specific grain surface. It was found that the electronic contribution to the total conductivity of the composites is reduced as compared to that of the basic Ce0.8Nd0.2O2-delta and BaCe0.8Nd0.2O3-delta materials. This leads to a better stability in the long-term redox-cycles in comparison with the basic oxides. Additionally, the conductivity in Ce0.8Nd0.2O2-delta decreases by 85%, whereas the conductivity of BaCe0.8Nd0.2O3-delta decreases by 30% after 2 redox-cycles for 200 h at 900 degrees C. The resulting conductivity degradation of the (1-x)Ce0.8Nd0.2O2-delta-xBaCe(0.8)Nd(0.2)O(3-delta) composite is no more than 15%. (C) 2014 Elsevier B.V. All rights reserved.