Crystal structure, electrical conductivity and Seebeck coefficient of Y(Mn,Ni)O3 solid solution

Solid solutions belonging to the Mn-rich region of the YNixMn1 -xO3 system have been studied. The powders were prepared by solid state reaction between the corresponding oxides. Sintered ceramics were obtained by firing at 1325-1350degreesC. The incorporation of 20 at.% Ni2+ to the yttrium manganite induces the formation of a perovskite-type phase, with orthorhombic symmetry and space group Pbmn. Increase of the Ni amount leads to an increase of the orthorhombicity factor b/a of the perovskite, up to an amount of 50 at.% Ni2+. Above this Ni amount, a biphasic system has been observed, with the presence of unreacted Y2O3. DC electrical conductivity measurement has shown semiconducting behaviour for this solid solution with perovskite-type structure. The room temperature conductivity increases with Ni up to similar to33 at.% Ni, and then decreases. Small polaron hopping mechanism controls the conductivity in these ceramics. Results are discussed as a function of the Mn3+/Mn4+ ratio for each composition. NTC thermistor capability and potential application as ceramic electrode for SOFCs are presented. (C) 2002 Elsevier Science Ltd. All rights reserved.