Combustion synthesis of Ln1-xMxCr0.9Ni0.1O3 (Ln = La and/or Nd; M = Sr and/or Ca; x≤0.25) perovskites as anode materials for SOFCs

A series of chromite perovskites with the general formula Ln1-xMxCr0.9Ni0.1O3 (Ln = La and/or Nd; M = Sr and/or Ca; x≤0.25) has been prepared by three combustion synthesis routes using a different fuel each time: glycine, urea and sucrose. In order to isolate the effect of divalent dopant concentration from the A cation steric effects, the whole group has a fixed mean A cation radius, ≈ 1.22 Å, and cation size disorder, σ(rA) ≈ 0.0001 Å, but variable doping x. Their crystal structure, microstructure, electrical properties and expansion coefficients have been investigated on the basis of their possible use as anode materials for intermediate temperature solid oxide fuel cells (SOFC). Important dependences of the cell parameters, grain size, the expansion coefficients and the conductivity with x and the used fuel are observed. The most interesting feature of these oxides is their negative dependence of the conductivity with x under H2 atmosphere: smaller conductivity is observed when doping is increased, which has not been previously reported.