ACICULAR CRYSTALS OF SODIUM TUNGSTEN BRONZES

The synthesis of sodium tungsten bronzes, NaxWO3, with emphasis on crystals with acicular morphology, has been examined experimentally. The acicular morphology is obtained for a range of compositions in which 0.15 less-than-or-equal-to x less-than-or-equal-to 0.28, and generally more than one crystal structure is present. At x almost-equal-to 0.28 the tetragonal II phase predominates. whereas at x almost-equal-to 0.15 an unknown structure is the major phase. Surprisingly, all the bronzes tested exhibited large solubilities in hot aqueous solutions of NH4OH.