| The result of fluorine analyzed by EPMA is always questioned by researchers. Four kinds of mineral samples containing known contents of F are chosen in this research for the analysis of fluorine with EPMA. Based on the analysis of the huge analyzed data, factors affecting the analysis of fluorine were investigated and the optimized conditions for fluorine analysis were designed to avoid or minimize the disadvantageous. Finally, a new method of the accurate analysis of fluorine in natural minerals was established.Compared with the traditional analyzing methods, the fluorine results analyzed with this new established method have several advantages. The spectrometer conditions are determined with LDE1 spectroscopic crystal. Measuring time at the peak position of fluorine is 10 s, and that at the background at-7.6mm and +4.4mm, the chosen positions at the both sides of the peak, is 5s. The stability of the X ray is required firstly to analyze fluorite, that means the need of both stable beam current and steady probe diameter, at least for a particular time. If the X ray is stable and strong, the auto mode can be used on the equipment, or it needs to be in manual mode. The pulse height analyzer(SCA) is used to exterminate the affect of hyper lines. The standard samples need to be those with both similar compositions and structure with the unknown samples. Topaz can only be used if the analyzing sample is also topaz. ZAF method is needed for calibrating calculation, and so is the uncertainty of the results.The method from this paper is used on apatite, and the result shows that the relative errors of fluorite are less than 10% and the errors of other elements are less than 2%. This sample is tested with 15 k V acceleration and 10 n A beam current. The determining limit of this test is about 600×10-6, and the uncertainty is 3.44%±0.44%. |
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