ω-Al2O3“ a microcrystalline ordered form of transition spinel alumina metastable up to 1200 °C
A new variety of alumina with micron-sized crystallization was obtained in mixture with other phases (a Si-doped transition alumina, α-Al2O3 and small amounts of mullite) by firing an Al2O3:SiO2 (12:1) gel at 1200 °C, beyond the domain of existence of the heretofore known transition aluminas. The s...
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| Veröffentlicht in: | Journal of solid state chemistry Jg. 312; S. 123303 |
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| 1. Verfasser: | |
| Format: | Journal Article |
| Sprache: | Englisch |
| Veröffentlicht: |
Elsevier Inc
01.08.2022
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| Schlagworte: | |
| ISSN: | 0022-4596, 1095-726X |
| Online-Zugang: | Volltext |
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| Zusammenfassung: | A new variety of alumina with micron-sized crystallization was obtained in mixture with other phases (a Si-doped transition alumina, α-Al2O3 and small amounts of mullite) by firing an Al2O3:SiO2 (12:1) gel at 1200 °C, beyond the domain of existence of the heretofore known transition aluminas. The so-called ω-Al2O3 transforms very slowly into α-Al2O3, even at such temperatures. According to X-ray diffraction /Rietveld analysis, the ordered orthorhombic (space group P21212) crystal structure corresponds to a 1 × 1.5 × 1 superstructure of the cubic spinel cell, with a 50 % deficiency in the occupancy of the octahedral sites in 1/3rd of the (010) layers. Though many arguments are in favor of a pure - or almost pure - form of alumina, no evidence can be given of the absence of silicon.
The 3-layer sequence of new ω-Al2O3 results from the insertion of a cation-deficient octahedra layer into the usual spinel array. [Display omitted]
•A new variety of micron-sized alumina.•Long-time metastability up to 1200 °C.•A novel form of fully ordered cation-deficient spinel structure. |
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| ISSN: | 0022-4596 1095-726X |
| DOI: | 10.1016/j.jssc.2022.123303 |