HIGH-TEMPERATURE X-RAY INVESTIGATION OF NATURAL COLUMBITES
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dc.contributor.author | Tarantino S.C. | |
dc.contributor.author | Zema M. | |
dc.contributor.author | Pistorino M. | |
dc.contributor.author | Domeneghetti M.C. | |
dc.date.accessioned | 2022-02-13T04:46:06Z | |
dc.date.available | 2022-02-13T04:46:06Z | |
dc.date.issued | 2003 | |
dc.identifier | https://elibrary.ru/item.asp?id=5103873 | |
dc.identifier.citation | Physics and Chemistry of Minerals, 2003, 30, 10, 590-598 | |
dc.identifier.issn | 0342-1791 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/35258 | |
dc.description.abstract | Structural investigations at high temperature were carried out on natural columbite samples across the join Fe(Nb0.95Ta0.05)2O6-Mn(Nb0.95Ta0.05)2O6. The samples were preliminarily annealed to attain the complete cation-ordered state and avoid the superimposition of the effects of cation ordering during high-temperature studies. Unit-cell parameters of three columbites with different XFe content were measured at regular intervals in the temperature range 25-900 °C using single-crystal X-ray diffraction techniques. The crystal structures of completely ordered ferrocolumbite and manganocolumbite were also refined from intensity data collected at room temperature, 300 and 600 °C. Structural thermal expansion coefficients show positive, linear expansion of a, b, c lattice constants and cell volume. In general, slightly higher expansion occurs along a and c directions. However, anisotropy decreases sharply with decreasing Fe content. Reversibility of thermal expansion in the investigated temperature range was checked by high-temperature diffraction studies under heating-up and cooling-down conditions. Impurities do not play an important role in thermal expansion of columbites; expansion coefficients measured on two crystals of the same sample characterized by different Ti content are in fact almost identical. Structural changes with temperature essentially affect bond lengths: volumes of both A and B octahedral sites increase linearly with temperature, whereas interpolyhedral geometrical parameters do not vary significantly. | |
dc.subject | COLUMBITE | |
dc.subject | HT X-RAY DIFFRACTION | |
dc.subject | THERMAL EXPANSION | |
dc.title | HIGH-TEMPERATURE X-RAY INVESTIGATION OF NATURAL COLUMBITES | |
dc.type | Статья |
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