Report on phase 2 of task 1.1: single phase synthesis to Lawrence Livermore National Laboratory for contract B345772
Near single phase pyrochlores and zirconolites (with Hf substituted for Zr) of the following compositions have been prepared. The results obtained are summarized in Table 1. Details of the fabrication method and the results are given: (1) Mg-doped zirconolite (Ca{sub 0.4}Gd{sub 0.6}HfMg{sub 0.3}Ti{sub 1.7}O{sub 7}), Al-doped zirconolite (Ca{sub 0.5}Gd{sub 0.5}HfAl{sub 0.5}Ti{sub 1.5}O{sub 7}), Ta-doped pyrochlore (CaGdTaTiO{sub 7}), Pu-pyrochlore (CaPuTi{sub 2}O{sub 7}), and 4M zirconolite from the Ca-Gd-Hf-Ti-0 system (Ca{sub 0.6}Gd{sub 0.8}Hf{sub 0.6}Ti{sub 2}O{sub 7} and Ca{sub 0.7}Gd{sub 0.6}Hf{sub 0.7}Ti{sub 2}O{sub 7}). All but the Ta-doped pyrochlore were prepared via the alkoxide-route. The Ta-pyrochlore was prepared via the oxide-route. Mo-doped pyrochlore could not be made single phase with significant amounts (0.4-0.6 formula units) of Mo present in the nominal batch pyrochlore formulation. If Ca was present powellite formed and Mg produced MgMoO{sub 4}. All samples basically contained a Ti-pyrochlore with a small amount (< 0.1 formula units) of Mo present, and a Mo-rich phase, which contained some Ti. Pu-brannerite (PuTi{sub 2}O{sub 6}) proved to be difficult to make. The Pu-brannerite did not form until the sintering temperature was close to the melting point, {approx} 1500 C. Regions rich in Pu-brannerite could be found in some samples, though these samples invariably contained regions rich in PuO{sub 2} and rutile. In a sample with 20 wt. 9% excess TiO{sub 2}, large Pu-brannerite grains were seen, presumably having grown from a melt. Work on Sn-doped pyrochlore and zirconolite end members is continuing as part of Task 1.4 and the results have been included here for interest. The sample of nominal composition CaSnTi{sub 2}O{sub 7} did not form pyrochlore or zirconolite. Instead perovskite, SnTiO{sub 4} and Ti-doped SnO{sub 2} were formed. The sample of nominal composition CaHfSn{sub 2}O{sub 7} was very refractory, with little densification occurring upon sintering, even after sintering at 1600 C. The samples remained porous and very soft and friable. The sample sintered at 1600 C appeared to be near single phase, but there was some compositional variation across the sample was observed. This sample was remilled and the refired at 1600 C for 16 hours in air. This sample was much denser. The XRD pattern indicated that it was composed mainly of zirconolite plus some minor (Hf,Sn)TiO{sub 4}. Samples of the Mg-doped zirconolite, Al-doped zirconolite, Ta-doped pyrochlore and two 4M zirconolite samples from the Ca-Gd-Hf-Ti-0 system have been shipped to LLNL.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15007521
- Report Number(s):
- UCRL-CR-139128; TRN: US0402089
- Resource Relation:
- Other Information: PBD: 23 Nov 1999
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AIR
FABRICATION
LAWRENCE LIVERMORE NATIONAL LABORATORY
MELTING POINTS
PEROVSKITE
PYROCHLORE
RUTILE
SINTERING
SYNTHESIS
X-RAY DIFFRACTION
ZIRCONOLITE