Electron energy-loss spectroscopy of silicate perovskite-magnesiowüstite high-pressure assemblages
Electron energy-loss spectroscopy of silicate perovskite-magnesiowüstite high-pressure assemblages
复制标题
硅酸盐钙钛矿-镁方石高压组合物的电子能量损失谱
DOI：
10.2138/am-2000-1014
复制
发表时间：
2000
影响因子：
3.1
通讯作者：
C. Colliex
中科院分区：
文献类型：
--
作者：
A. Gloter;F. Guyot;I. Martinez;C. Colliex
摘要利用电子能量损失谱（EELS）研究了多砧压机和金刚石对顶砧装置合成的硅酸盐钙钛矿-镁橄榄石组合体。在Fe和Si L2，3边缘和低损耗（<50 eV）域中收集结晶硅酸盐钙钛矿及其后非晶化相以及镁钨铁矿的光谱。确保非常低的光束剂量的线光谱技术允许在非晶化之前从晶体钙钛矿收集高质量的光谱，并允许表征钙钛矿和镁钨铁矿的共存晶体。在Si L2，3边缘的光谱表明，电子束诱导的硅酸盐钙钛矿的非晶化伴随着从六倍到四倍的硅原子的氧配位的变化。在Fe L2，3边的光谱表明，Fe 2+是橄榄石、林伍德石和镁钨铁矿中Fe的主要存在形式，而Fe 3+在结晶硅酸盐钙钛矿及其非晶化产物中占主导地位。在这些样品中观察到的镁钨铁矿和硅酸盐钙钛矿接触，铁3+强烈分配到硅酸盐相。仔细的实验扣除零损耗峰的非布拉格获取的电子能量损失谱，使高质量的低损耗谱收集从结晶硅酸盐钙钛矿和镁钨铁矿。在镁橄榄石，带间跃迁的特点是，导致7.8 eV的测量间隙，与以前的理论计算一致。在10 eV和12.5 eV的带间跃迁也很好地解决了结晶硅酸盐钙钛矿，导致约9.5 eV的间隙。
Abstract Silicate perovskite-magnesiowüstite assemblages synthesized from natural olivine in the multianvil press and diamond-anvil cell were studied by electron energy-loss spectroscopy (EELS). Spectra of crystalline silicate perovskite, and its post-amorphization phase, as well as magnesiowüstite were collected at the Fe and Si L2,3 edge, and in the low loss (<50 eV) domain. The technique of line spectra ensuring very low beam doses allows good quality spectra to be collected from crystalline perovskite prior to amorphization and permits characterization of coexisting crystals of perovskite and magnesiowüstite. Spectra at the Si L2,3 edge show that the beam-induced amorphization of silicate perovskite is accompanied by a change from sixfold to fourfold oxygen coordination of silicon atoms. Spectra at the Fe L2,3 edge show that Fe2+ is the major form of Fe in olivine, ringwoodite, and magnesiowüstite, whereas Fe3+ is dominant in crystalline silicate perovskite and its amorphization products. In magnesiowüstite and silicate perovskite observed in contact in these samples, Fe3+ is strongly partitioned into the silicate phase. Careful experimental substraction of zero-loss peak by off Bragg acquisition of electron energyloss spectra allows good quality low loss spectra to be collected from crystalline silicate perovskite and magnesiowüstite. In magnesiowüstite, interband transitions are well characterized, leading to a measured gap of 7.8 eV, in agreement with previous theoretical calculations. Interband transitions at 10 eV and 12.5 eV are also well resolved in crystalline silicate perovskite, leading to a gap of about 9.5 eV.