Abstract
The TTB-type (tetragonal tungsten bronze) structure of Ta8W9O47has been investigated for two different processing temperatures (T= 1200 and 1400°C) using X-ray powder diffraction and TEM methods. The Guinier patterns for both temperatures show the reflections of the TTB-type structure. Additionally, the product obtained at 1400°C exhibits the reflections of a threefold TTB-type superstructure. HRTEM images of this specimen (along [001]) show that the superstructure originates from a systematic arrangement of PCs (pentagonal columns) in the TTB-type framework which is also known from Nb8W9O47. For 1200°C, the electron diffracton patterns (along [001]) exhibit circular diffuse scattering around the basic reflections and additional superstructure reflections can be observed at the intersections of the circles with both tetragonal axes. A structural model for the low-temperature phase has been derived from HRTEM images. It is shown (using Fourier analysis) that the diffuse scattering is caused by a disordered distribution of the PCs. In case of a locally incomplete reaction, the arising defect structure of a tungsten-rich crystal area is characterized using HRTEM.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
