In situ quantitative analysis of beryllium by EPMA: analytical conditions and further insights into beryllium geochemistry

Abstract

Accurate in situ analysis of beryllium (Be) is still a technical bottleneck in the fields of geoscience and materials science. In this study, we explored the analytical conditions of Be by using EPMA's state analysis of Be in different types of Be minerals (oxides, silicates, borates, and phosphates). Monte Carlo simulations suggested that a low accelerating voltage is conducive to the in situ analysis of Be. Optimized analytical conditions for Be minerals are obtained: 10 kV accelerating voltage, 50 to 100 nA beam current for hydrous Be minerals, greater than 100 nA beam current for anhydrous Be minerals, min beam size, PHA mode, and selecting the same Be minerals or similar Be minerals with the same structural environment of Be atoms as standard samples. Moreover, the analytical results of eleven types of Be minerals are close to the theoretical value or within the error range, showing that the in situ analysis of Be is completely feasible under the optimized analytical conditions. The low intensity of Be Kα under EPMA is most likely caused by the polyhedron structural environment, such as coordination, order and disorder, etc., and the influence of other chemical compositions (O, OH, and P) in Be minerals. The Fermi level decrease of E_L in Be–O bonds results in the right shift of the X-ray peaks of Be. Overall, these experimental results and conclusions not only are helpful in revealing the mineralogical and geochemical properties of Be but also provide further insights into the distribution and metallogenic mechanism of Be in deposits.