Electron microprobe analysis of cryolite

F Guimarães, P Bravo Silva, J Ferreira, A P Piedade, M T F Vieira
2014 IOP Conference Series: Materials Science and Engineering  
A sample of cryolite was studied with a JEOL JXA 8500-F electron microprobe under several operating conditions. A TAP crystal was used to analyse Na and Al and a LDE1 crystal to analyse F. As F and Na are both highly volatile elements, special care must be taken during analysis. The measurement order of Na, F and Al is not irrelevant and optimum conditions may also result in different combinations of accelerating voltage, beam current, beam size or counting times. Some X-Ray signals were
more » ... d in order to investigate the behaviour of the Na Kα and F Kα X-ray counts with the elapsed time. The incident beam current was also recorded at the same time. In a clear contrast to what happens in the EPMA analysis of aluminosilicates and silicate glasses, we found that Na X-ray counts increase with time. This grow-in of X-rays intensities for sodium in cryolite depends on the operating conditions and is accompanied by a strong migration of fluorine from the beam excitation volume, leading to a decrease in F X-ray counting rates. It was also observed that higher incident beam currents induce higher radiation damage in the mineral. The current instability is consistent with possible electron induced dissociation in the cryolite structure. An analytical protocol was achieved for 6 kV and 15kV accelerating voltage.
doi:10.1088/1757-899x/55/1/012006 fatcat:el4qm3nvujgb7n725sh7tdgic4