Annealing of natural metamict zircons: II high degree of radiation damage

In situ time-dependent high-temperature X-ray powder diffraction was used to study the amorphous to crystalline transition in natural zircons which are characterized by a high degree of radiation damage. It was possible to distinguish two stages of the annealing process: (i) the recovery of the heavily disturbed but still crystalline domains and (ii) the recrystallization of the amorphous regions. The first stage is very fast under the chosen experimental conditions and, at least apparently, is not thermally activated. The second stage is a diffusion-controlled process, whose products (zircon or zircon and zirconia phases) are strongly correlated to the annealing temperature.     

Channel structure in the new BiCoPO5. Comparison with BiNiPO5. Crystal structure,lone pair localisation and infrared characterisation

The new compound BiCoPO₅, monoclinic, P2₁/n, a = 7.2470(1) A, b = 11.2851(2) A, c = 5.2260(1) A and β = 107.843(1) °, Z = 4, was synthesised and structurally characterised by powder X- ray diffraction and infrared spectroscopy. It is isostructural with bismuth nickel oxyphosphate BiNiOPO₄. The crystal structure is built from a complex tridimensional assembly of (Co/Ni)₂O₁₀ dimers linked by PO₄ groups. This forms large tunnels running along c which host Bi³⁺ cations. Smaller tunnels running along a and crossing the latter were also evidenced. It is noteworthy that the original BiNiPO₅ lattice is appreciably increased with Co²⁺ cations as the transition metal. This feature is essentially pointed out by the Co-O longer distances. The Bi³⁺ cation is surrounded by a strongly distorted oxygen octahedron. Reducing the BiO bonds to the three shortest, Bi environment can be considered as tetrahedral considering the BiO₃Lp polyhedron, Lp = 6s² lone pair (Lp). The lone pair localisation was performed from electrostatic interactions and revealed Lp - Bi distance of 0.68 A and 0.58 A, for Co²⁺ and Ni²⁺ compounds respectively. The infrared spectra of the two compounds are essentially the same and only show slight shifts of the significant bands.     

Classification and Prediction of Geological Samples by Principal Component Analysis

The principal component analysis is an ancient multivariate statistical method[1]. It is extensively used in spectrometry with the popularization of computer and development of the method of chemometrics. It is regarded as an effective method of multivariate statistical analysis. The principal component analysis is universally included in common program package of multivariate statistical analysis. The method, as well as other multivariate calibration methods, combined with artificial neural networks forms the foundation of the chemometrics.     

X射线荧光在地质材料卤族元素分析中的应用评介

卤族元素氟、氯、溴、碘广泛分布在地圈、水圈和生物圈,它们是矿产资源,也是许多地学研究的信息载体,更与人类生活紧密相关.卤族元素分析是地质分析的重要组成部分,而X射线荧光光谱分析方法在当今的卤族元素分析中占有重要地位.本文收集我国1988年—2020年间X射线荧光光谱分析地质材料氟、氯、溴、碘的文献126篇,在简述卤族元...     

电弧直读光谱仪的开发与应用

介绍一种国内首创的电弧直读光谱仪。该仪器由交/直流电弧激发光源、凹面光栅分光系统、光电倍增管接收器及智能测控系统所组成。研制成功地质样品专用的"交流电弧直读光谱仪"和高纯金属专用的"直流电弧直读光谱仪"可取代1m或2m光栅摄谱仪,省去了光谱相板、洗相及译谱等繁琐的操作程序。在优化的分析条件下,可直接对粉末状地球化学样品及高纯金属氧化物中的多种微量元素同时进行直读光谱测定,具有灵敏、准确、快速的特点,各项技术指标符合所属领域的"国家标准"及"行业规范"的要求。现已有多家使用单位采用"交流电弧直读光谱仪"分析了十几万件地球化学样品中的银、锡和硼等元素,取得了良好的应用效果。     

Study of photo-elastic behaviour of mixed alkali halides

The present paper deals with the analysis of strain optical constants of the mixed alkali halide crystals.