  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 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 Na-doped compound is explained in terms of a different
spin-state for the Co ions within this structure. The higher conductivity and
the absence of anomalies in the thermal expansion makes the Ca-doped compound
more attractive than the pure NdCoO3 in view of possible applications. The
experimental data and the Co environment analysis here discussed, in particular
bond lengths distortion and bending angles, are fully consistent with a spin
state (low to intermediate) transition in NdCoO3
