Electrical Properties of Some Dilute Cubic Sodium Tungsten Bronzes

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Abstract
The preparation and electrical properties are described for cubic NaxWO3 single crystals of the compositions x=0.363, 0.291, and 0.234. Specimens were prepared by diffusing sodium from single crystals of Na0.687WO3. The composition and homogeneity of the crystals were established by x‐ray powder and back‐reflection Laue photographs. The electrical resistivity‐temperature plots show a more complex electronic behavior than had been expected for dilute NaxWO3 on the basis of earlier work; Na0.291WO3 and Na0.234WO3 exhibit resistivity minima at about 150° and 320°K, respectively, with characteristics similar to that of degenerate semiconductors. A polycrystalline sample of Na0.025WO3, having a room‐temperature resistivity of 3×10—3 ohm cm and a Seebeck coefficient of —270 μv/deg, is also described.