Structural Studies of Calcium Tungsten Bronzes, CaxWO3, Formed at High Pressure

✍ Scribed by N.D. Zakharov; P. Werner; I.P. Zibrov; V.P. Filonenko; M. Sundberg

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 495 KB
• Volume: 35
• Category: Article
• ISSN: 0232-1300
• DOI: 10.1002/1521-4079(200007)35:6/7<713::aid-crat713>3.0.co;2-z

✦ Synopsis

The structure of a new calcium intergrowth tungsten bronze, Ca x WO 3 , prepared at P = 80 kbar and T = 1670 K, has been studied by high-resolution transmission electron microscopy and supplementary techniques. The unit-cell dimensions, determined from X-ray powder data, are: a = 10.1500( ), b = 7.4232( ) and c = 3.7915(4) Å. The crystal structure is of (n)-ITB type with n = 2. It is isotypic with those recently reported for the RE x WO 3 bronzes (RE = Pr and Nd) prepared at P = 50 kbar. Combined electron diffraction and energy-dispersive X-ray spectroscopy (EDX) studies of thin crystallites showed that the hexagonal tunnels were less than half-filled with Ca atoms (x ≈ 0.07±0.01). Electron diffraction patterns revealed ordered superstructures of (2)-ITB as well as an order-disorder transformation under the intense electron beam. A calcium bronze (Ca≈ 0.12 WO 3 ) with an hexagonal tungsten bronze structure (HTB) was also observed in the sample.