Analytical electron microscopy of the Garnet-Perovskite transformation in a laser-heated diamond anvil cell
Analytical electron microscopy of the Garnet-Perovskite transformation in a laser-heated diamond anvil cell
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激光加热金刚石砧池中石榴石-钙钛矿转变的分析电子显微镜
DOI：
10.1029/gm101p0409
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Nobumasa Funamori
中科院分区：
文献类型：
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作者：
K. Fujino;N. Miyajima;T. Yagi;T. Kondo;Nobumasa Funamori
对从激光加热金刚石砧池实验中回收的薄箔的实验分析电子显微镜程序进行了检查。分析电子显微镜的X射线微分析证明，电子束的扩散对于钙钛矿来说是必要的，以防止电子束照射期间元素的选择性去除。通过使用针对箔厚度校准的实验确定的 K 值来改进计算的成分。通过这种分析程序，对在 30-50 GPa 下转化的天然镁铝榴石石榴石的回收样品进行了检查。富铁（Fe/(Fe+Mg)∼0.19）镁铝榴石石榴石在∼30 GPa时转变为斜方钙钛矿（一种未知的富铝相）和辉石，而在压力≥∼33 GPa时它们完全转变为斜方钙钛矿。然而，贫铁的镁铝榴石石榴石即使在 50 GPa 的压力下也会分解成钙钛矿（未知的富铝相）和辉石。这种差异可能归因于原材料石榴石中的 Fe 和 Al 含量。在富铁样品中，具有相同成分的斜方钙钛矿相和铌酸锂相的交替片层表明钙钛矿相向铌酸锂相的亚稳态转变。
Experimental analytical electron microscopy procedures for thin foils recovered from laser-heated diamond anvil cell experiments have been examined. The X ray microanalysis by an analytical electron microscope proved that spreading of the electron beam was necessary for perovskite to prevent the selective removal of elements during the electron beam irradiation. The calculated compositions are improved by using the experimentally determined K values calibrated for the foil's thickness. With this analytical procedure, recovered samples of natural pyrope garnets transformed at 30-50 GPa were examined. Iron-rich (Fe/(Fe+Mg) ∼ 0.19) pyrope garnets are transformed into orthorhombic perovskite, an unknown Al-rich phase, and stishovite at ∼30 GPa, whereas they are transformed wholly into orthorhombic perovskite at pressures ≥∼33 GPa. However, iron-poor pyrope garnets decompose into perovskite, the unknown Al-rich phase, and stishovite even at 50 GPa. This difference may be attributed to the Fe and Al contents in starting material garnets. In an iron-rich sample, alternating lamellae of orthorhombic perovskite and lithium niobate phases with the same composition suggest the metastable transformation of perovskite to lithium niobate phase.