Structural and thermal investigation of gadolinium gallium mixed oxides obtained by coprecipitation: Observation of a new metastable phase
- Dipartimento di Chimica, Universita di Sassari, via Vienna n. 2, I-07100 Sassari (Italy)
- Dipartimento Scientifico e Tecnologico, Universita di Verona, Ca' Vignal 1, strada le Grazie 15, I-37134 Verona (Italy)
Polycrystalline gadolinium gallium mixed oxides were prepared by coprecipitation and annealing at various temperatures below 1000 deg. C. The oxide materials appear to be X-ray amorphous after a heat treatment at 500 deg. C for 30 h, but after 30 h at 800 and 900 deg. C a major, unreported, hexagonal phase, isostructural with TAlO{sub 3} compounds (where T=Y, Eu, Gd, Tb, Dy, Ho, Er) appears to crystallize. On the other hand, a highly energetic mechanical treatment of the amorphous powder previously annealed at 500 deg. C changes considerably the shape and position of exothermal events occurring in the range from 700 up to 900 deg. C. Subsequent annealing at 900 deg. C of the mechanically treated powder gives rise to the complete formation of the Gd{sub 3}Ga{sub 5}O{sub 12} garnet structure at the expense of the hexagonal phase and of the minor Gd{sub 4}Ga{sub 2}O{sub 9} oxide phase. However, a 7.0 wt% contamination is found to be due to tetragonal zirconia coming from vials and balls colliding media. The garnet phase may have strong deviations from the nominal stoichiometry of the garnet, as suggested by the refined lattice parameter obtained from the powder diffraction patterns and by the remarkable absence of intensity relative to the (220) Bragg peak position.
- OSTI ID:
- 20729030
- Journal Information:
- Journal of Solid State Chemistry, Vol. 178, Issue 7; Other Information: DOI: 10.1016/j.jssc.2005.05.017; PII: S0022-4596(05)00208-2; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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