Simultaneously enhanced thermoelectric power and reduced resistivity of NaxCo2O4 by controlling Na nonstoichiometry

Electrical resistivity (rho) 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 rho monotonically decreased, while the value of S increased. For the x = 1.5 sample, S reached a value as high as similar to 120 muV/K (at 300 K). (C) 2001 American Institute of Physics.