Effect of the Cobalt Substitution on the Structure and Properties of the Layered Sodium Cobaltate Derivatives

Using solid-state reactions method the ceramic samples of Na0.89Co0.9M0.1O2 (M = Sc, Ti, Cr–Zn, Mo, W, Pb, Bi) solid solutions had been prepared, their lattice constants had been determined and their microstructure, thermal expansion, thermal conductivity, electrical conductivity and thermo-EMF had been measured, and their power factor and figure-of-merit values had been calculated. Effect of the cobalt substitution by other metals in the Na0.89CoO2 on the crystal structure and physicochemical and functional properties of its derivatives was analyzed. It was found that Na0.89Co0.9M0.1O2 cobaltates are the p-type conductors, which linear thermal expansion coefficient (LTEC) values varied within (1.24–2.05)·10-5 K-1. It was found that the best thermoelectric properties among the oxides studied possessed Na0.89Co0.9Ni0.1O2 and Na0.89Co0.9Bi0.1O2 solid solutions which power factor and figure-of-merit estimated values at 1100 K are equal to 0.919 and 0.660 mW/(m·K) and 1.12 and 0.83 respectively.