High-pressure Raman spectroscopic studies of ulvöspinel Fe2TiO4
High-pressure Raman spectroscopic studies of ulvöspinel Fe2TiO4
复制标题
DOI：
10.2138/am.2011.3707
复制
发表时间：
2011-08
影响因子：
3.1
通讯作者：
A. Kyono;M. Ahart;T. Yamanaka;S. Gramsch;H. Mao;R. Hemley
中科院分区：
文献类型：
--
作者：
A. Kyono;M. Ahart;T. Yamanaka;S. Gramsch;H. Mao;R. Hemley
摘要我们报道了在室温下，在高达57 GPa的静压条件下，在金刚石压砧室中原位拉曼光谱研究的ulvöspinel。在1GPa下，在493和681 cm-1附近清晰地观察到两个模。在立方尖晶石结构中，较低的频率峰可以被分配给F2 g对称的模式，较高的频率峰可以被分配给A1 g对称的模式。尽管根据因子群分析，尖晶石结构的Fd 3 m空间群中存在五个拉曼活性模式（A1 g +Eg+3F 2 g），但在测量中无法明确观察到其余三个模式。在拉曼光谱中的峰的位置和形状与在环境条件下测量的那些一致。随着压力的增加，A1 g和F2 g模式的频率不断增加，直到9 GPa的压力导数分别为2.5和2.1 cm-1/GPa。在此压力范围内没有观察到晶体对称性的明显退化或结构变化。当压力增加到约20 GPa时，F2 g模式分裂成B1 g +Eg模式，然后分裂成B1 g + B2 g + B3 g模式。拉曼谱带的强度由于四方-斜方相转变而逐渐减弱。这种模式在29 GPa的压力下完全消失。紫外尖晶石的拉曼光谱最显著的特征是压缩导致来自F2 g对称性的拉曼活性模的消光。在57 GPa以下，只能连续观察到一个A1 g模的峰。A1 g模的峰移及其半高宽（FWHM）值表明在30 GPa附近发生了另一个相变。红尖晶石的拉曼光谱与ZnCr_2O_4和ZnFe_2O_4尖晶石的拉曼光谱一致。
Abstract We report in situ Raman spectroscopic studies of ulvöspinel in a diamond-anvil cell under hydrostatic conditions up to 57 GPa at room temperature. Two modes near 493 and 681 cm-1 are observed clearly at 1 GPa. In the cubic spinel structure, the lower frequency peak can be assigned to a mode of F2g symmetry and the higher frequency peak can be assigned to a mode with A1g symmetry. The remaining three modes could not be observed unambiguously in the measurements, although there are five Raman-active modes (A1g+Eg+3F2g) in the Fd3̅m space group of the spinel structure according to factor group analysis. The peak positions and shapes in the Raman spectra agree well with those measured under ambient conditions. With increasing pressure, the frequencies of the A1g and F2g modes increase continuously up to 9 GPa with pressure derivatives of 2.5 and 2.1 cm-1/GPa, respectively. There is no obvious degradation of crystal symmetry or structural change observed within this pressure range. Upon increasing pressure to ~20 GPa, the F2g mode splits into B1g+Eg modes, and then into B1g+B2g+B3g modes. The intensities of the Raman bands gradually decrease due to the tetragonalorthorhombic phase transition. This mode completely disappears at a pressure of 29 GPa. The most striking characteristic of the Raman spectrum of ulvöspinel is that compression leads to the extinction of the Raman-active mode derived from F2g symmetry. Only one peak resulting from the A1g mode can be observed continuously up to 57 GPa. The peak shift derived from the A1g mode and its full-width at half maximum (FWHM) values suggests another phase transition occurring around 30 GPa. The Raman spectrum of ulvöspinel is in good agreement with the spectra of ZnCr2O4 and ZnFe2O4 spinels.