SHORT- AND LONG-RANGE ORDERING IN THE ILMENITE-HEMATITE SOLID SOLUTION
- DSpace Home
- →
- Геология России
- →
- ELibrary
- →
- View Item
JavaScript is disabled for your browser. Some features of this site may not work without it.
dc.contributor.author | Harrison R.J. | |
dc.contributor.author | Redfern S.A.T. | |
dc.date.accessioned | 2021-03-30T10:40:27Z | |
dc.date.available | 2021-03-30T10:40:27Z | |
dc.date.issued | 2001 | |
dc.identifier | https://www.elibrary.ru/item.asp?id=872510 | |
dc.identifier.citation | Physics and Chemistry of Minerals, 2001, 28, 6, 399-412 | |
dc.identifier.issn | 0342-1791 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/27167 | |
dc.description.abstract | Magnetic and cation ordering in the ilmenite-hematite solid solution (FeTiO3–Fe2O3) has been studied using in-situ high-temperature time-of-flight neutron powder diffraction. Synthetic samples containing 60 and 65% FeTiO3 (ilm60 and ilm65, respectively) were heated under vacuum up to 1000°C and their magnetic structure, crystal structure and cation distribution were determined via Rietveld refinement. The quenched starting materials display diffuse superlattice reflections, indicative of short-range cation order. The short-range ordered structure is interpreted with the aid of statistical simulations to be a fine-scale alternation of ordered and antiordered ilmenite-like twin domains, separated by hematite-like twin-domain boundaries (TDBs). Peak width analysis demonstrates that the twin domains have a pronounced shape anisotropy, with average lengths of 20 ± 1 and 60 ± 2 A along the c-axis, and 100 ± 9 and 100 ± 4 A along in ilm60 and ilm65, respectively. Long-range order increases initially by a process of domain coarsening as the quenched samples are heated below the cation order-disorder temperature, Todhe degree of order then decreases as they are heated through the transition. This leads to a kinetic relaxation behaviour, in which the observed rate of ordering is determined by the balance between the rate of coarsening and the rate of disordering within the domains. A phenomenological kinetic model is developed, which provides an excellent description of the observed behaviour in both samples. Once long-range order has been established, the equilibrium degree of order as a function of temperature is well described by a modified Bragg-Williams model, yielding values of Tod0 ± 20 °C and 911 ± 20°C for ilm60 and ilm65, respectively. Analysis of the magnetic scattering and spontaneous strain demonstrates that short-range magnetic order remains at temperatures well above the bulk Curie temperatures (Tc=178°C and 143°C in ilm60 and ilm65, respectively). This indicates significant magnetic heterogeneity in the samples, which may be related to the presence of a high density of Fe-enriched TDBs in the quenched material. | |
dc.title | SHORT- AND LONG-RANGE ORDERING IN THE ILMENITE-HEMATITE SOLID SOLUTION | |
dc.type | Статья |
Files in this item
Files | Size | Format | View |
---|---|---|---|
There are no files associated with this item. |
This item appears in the following Collection(s)
-
ELibrary
Метаданные публикаций с сайта https://www.elibrary.ru