Incorporation of REE into leucophanite: a compositional and structural study
Incorporation of REE into leucophanite: a compositional and structural study
复制标题
将 REE 掺入白磷矿中：成分和结构研究
作者：
H. Friis;T. Balić ;C. Williams;R. García
本文研究了9个天然白云母（NaCaBeSi2O6F）的晶体结构和10个天然白云母的化学组成。分析的样品显示出很大的成分变化，微量元素丰度> 50，000 ppm，主要是由于稀土元素（REE）。从这些数据中，我们提出了一个替代方案的纳入稀土元素的Ca，与额外的Na取代Ca和空位的产生，以确保电荷平衡。在一些样品中观察到成分环带，这种环带与阴极发光的变化。九个分析样品的晶体结构都可以在空间群P212121中进行细化。我们没有发现证据的对称性减少与微量元素浓度的增加。观察到各种孪晶组合，这些似乎与结晶条件有关，而不是结构或化学因素。
Abstract The crystal structures of nine, and the chemical compositions of ten, natural samples of leucophanite, ideally NaCaBeSi2O6F, were investigated. The analysed samples display a large compositional variation with trace-element abundances >50,000 ppm, primarily due to rare earth elements (REE). Fromthese data, we propose a substitution scheme for the incorporation of REE for Ca, with additional Na substituting for Ca and the generation of vacancies to ensure charge balance. Compositional zonation was observed in some samples; this zonation correlates with variations in cathodoluminescence. The crystal structure of the nine analysed samples could all be refined in space group P212121. We found no evidence for a reduction of symmetry with increased trace-element concentration. Various twin combinations were observed and these seem related to crystallization conditions rather than structural or chemical factors.