Sequential high-pressure transformations of FeGeO3 high-P clinopyroxene (C 2 /c) at temperatures up to 365 ¯C
Sequential high-pressure transformations of FeGeO3 high-P clinopyroxene (C 2 /c) at temperatures up to 365 ¯C
复制标题
FeGeO3 高磷单斜辉石 (C 2 ©/c) 在高达 365 ¯C 温度下的连续高压转变
DOI：
10.1007/s002690100174
复制
发表时间：
2001
影响因子：
1.4
通讯作者：
T. Yamanaka
中科院分区：
文献类型：
--
作者：
T. Hattori;T. Tsuchiya;T. Nagai;T. Yamanaka
摘要：为了阐明高磷单斜辉石 (C2/c) 在原子不被热激活的动力学低温下的高压转变，利用同步辐射源和 TEM 观察，通过粉末 X 射线衍射和 TEM 观察，研究了 FeGeO3 单斜辉石 (C2/c) 在高达 20 GPa 的压力和 365 °C 的压力下的转变过程。在室温下，随着压力增加至 20GPa，FeGeO3 高磷单斜辉石 (C2/c) 可逆地转变为新的高压相 FeGeO3(II)。当温度升高至 365°C 时，该相在约 2 小时内迅速转变为 FeGeO3 钛铁矿。 X射线衍射图谱强度分析表明，FeGeO3(II)高压相具有介于单斜辉石和钛铁矿之间的中间结构：阳离子排列与单斜辉石相似，氧排列与钛铁矿相似。这些多晶型物晶体结构的比较表明，单斜辉石到 FeGeO3(II) 和 FeGeO3(II) 到钛铁矿的转变分别是通过氧堆积的轻微变形和阳离子的短程移动来进行的。结果表明，这种高磷单斜辉石在低温条件下通过低活化能路径转变为钛铁矿。
Abstract In order to elucidate high-pressure transformations of high-P clinopyroxene (C2/c) at kinetically low temperature where atoms are not thermally activated, the transformation processes of FeGeO3 clinopyroxene (C2/c) have been investigated at pressures up to 20 GPa and 365 °C by powder X-ray diffraction using a synchrotron radiation source and TEM observation. With increasing pressure up to 20 GPa at room temperature, FeGeO3 high-P clinopyroxene (C2/c) reversibly transforms into a new high-pressure phase, FeGeO3(II). On increasing the temperature up to 365 °C, this phase rapidly transforms into FeGeO3 ilmenite within about 2 h. Intensity analysis of the X-ray diffraction pattern reveals that the high-pressure phase of FeGeO3(II) has an intermediate structure between clinopyroxene and ilmenite: the cation arrangement is similar to that of clinopyroxene and the oxygen arrangement is similar to that of ilmenite. The comparison of the crystal structures of these polymorphs suggests that clinopyroxene to FeGeO3(II) and FeGeO3(II) to ilmenite transformations are performed by the slight deformation of the oxygen packing and the short-range movement of cations, respectively. It is shown that this high-P clinopyroxene transforms into ilmenite through a low-activation energy path under the low-temperature condition.