Electrical resistivity (ρ) and thermoelectric power (S) were measured for NaxCo2O4 samples with various Na contents (x). A highly precise control of Na nonstoichiometry was facilitated by optimizing the synthesis procedure. With increasing x, the absolute value of ρ monotonically decreased, while the value of S increased. For the x=1.5 sample, S reached a value as high as ∼120 μV/K (at 300 K).

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Polycrystalline samples of Sr NbO, (0.75~x~0.90) have been successfully synthesized by a solidstate reaction technique using TiO as a reducing agent. Powder x-ray-diffraction analysis indicated that the samples with x 0.80 were single phase of the cubic perovskite structure. Electrical resistivity of each sample exhibited metallic behavior at temperatures below 300 K. For the samples with x &0.90, the magnetic susceptibility was nearly temperature independent (Pauli paramagnetic), while the sample with x =0.90 showed a Curie-Weiss behavior. Since the thermoelectric power coefficient (S) was found to be negative for all the samples in the temperature range between 10 and 300 K, the dominant charge carriers in Sr Nb03 (0.75~x~0.90) were thought to be electrons. On the contrary, the nonlinear temperature dependence of S indicated that electrons in Sr"Nb03 were not simply metallic but rather similar to those in amorphous metals.