C. Tealdi, L. Malavasi, F. Gozzo
Jun 26, 2007
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Journal
Chemistry of Materials
Abstract
This study presents correlations between the structural and transport properties of pure and doped neodymium cobaltate, a compound of great interest for its foreseen applications as a catalyst, sensor, and thermoelectric material. Neutron and X-ray powder diffraction data have been combined to carefully determine lattice constants and atomic positions, and four-probe direct current conductivity and thermoelectric power measurements allowed us to follow the thermal evolution of the transport properties of these compounds. The dramatic improvement of the room-temperature conductivity of Nd0.8Ca0.2CoO3 with respect to the pure and the sodium-doped compound is explained in terms of a different spin-state for the cobalt ions within this structure. The higher conductivity and the absence of anomalies in the thermal expansion makes the calcium-doped compound more attractive than the pure NdCoO3, in view of possible applications. The experimental data and the cobalt environment analysis here discussed, in particu...