Isomorphy of structural phase transitions in LiTaOSiO4, LiTaOGeO4 and titanite, CaTiOSiO4 |
| |
Authors: | Thomas Malcherek Anne Bosenick Michael Fechtelkord |
| |
Institution: | a Mineralogisches Institut, Universität Heidelberg, Im Neuenheimer Feld 236, D-69120 Heidelberg, Germany b Institut für Mineralogie, Universität Münster, Corrensstr. 24, D-48149 Münster, Germany c Institut für Geowissenschaften, Universität Kiel, Olshausenstr. 40, Kiel, Germany d Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany |
| |
Abstract: | Structural phase transitions in LiTaOGeO4 (LTGO) and LiTaOSiO4 (LTSO) have been observed using differential scanning calorimetry, X-ray diffraction and MAS NMR spectroscopy. LTGO transforms from P21/c to C2/c space group symmetry at , while the isomorphic transition occurs at in LTSO. An analogous phase transition is known to occur in the structurally related mineral titanite, CaTiOSiO4. Spontaneous strain accompanying this phase transition in LTSO is significantly stronger than in titanite. As in titanite non-vanishing strain components are observable for Tc<T<Ti, with a similar ratio Ti/Tc. MAS NMR spectroscopy in combination with computation of the electric field gradient by first principle methods confirms that the tetrahedral Li coordination environment is retained during the phase transitions in LTGO and in LTSO. In LTSO substantial motional narrowing is observed, indicating increased mobility of the Li cation above . The narrowing of the spinning sidebands is significantly modified immediately above and below the critical temperature. |
| |
Keywords: | Phase transition Antiferroelectric Titanite Sphene Order-disorder |
本文献已被 ScienceDirect 等数据库收录! |
|