Electrical Resistivity of Cubic Sodium Tungsten Bronze

The electrical resistivities of the nonstoichiometric compounds NaxWO3 have been measured as a function of sodium concentration from x=0.48 to x=0.88, and as a function of temperature from T=4°K to T=873°K. The minimum in electrical resistivity near x=0.75, which had been reported by earlier investigators, was absent in single crystals which were selected to be electrically homogeneous. Above room temperature, the electrical conductivity increased approximately linearly with sodium concentration; at liquid-helium temperatures, the electrical conductivity increased approximately as the fourth power of sodium concentration.