High-temperature transport properties of Nb and Ta substituted CaMnO3 system

Polycrystalline samples of CaMn1-xMxO3 (M=Nb and Ta, 0less than or equal toxless than or equal to0.30) were studied by means of X-ray diffraction, electrical resistivity (rho), thermoelectric power (S) and thermal conductivity (kappa) at high temperature. Both Nb and Ta substitutions lead to increasing lattice parameters a and b and decreasing c. The Nb-doped samples possess lower rho and \S\ than that of Ta-doped samples, which is suggested to be related to the effective d-p hybridization between Nb and O. A good thermoelectric performance with the figure of merit Z = 0. 8 x 10(-4) K-1 at 1000 K was obtained for CaMn0.96Nb0.04O3. (C) 2003 Elsevier B.V. All rights reserved.