![]() ![]() Measurements were taken from a sample of magnetite and two kinds of hematite. While it is always gratifying if the results match the expected quantitative values, if the peaks can be measured precisely and consistently then it should always be possible to apply the appropriate corrections, with or without use of standards, to get the accurate quantitative results. The goal of this work is to analyze a number of different metal oxides, measuring both the metal and oxygen peaks, and look for consistency and precision in the result. These changed capabilities, especially the ability to acquire large numbers of x-ray photons in a short time, present a good opportunity to revisit the old assumptions and see how much things have changed. It is easy to count at rates of many tens of thousands of counts per second while collecting a clean spectrum. This detector features improved soft x-ray measurement capabilities but most importantly it allows for very high count rates while maintaining good energy resolution. Since the middle of the 1990s a new EDS detector technology has been developed called the Silicon Drift Detector. Assuming an upper limit to the acquisition time of a few minutes put a limit on the x-rays the number of x-rays acquired and, therefore, put a limit on the precision of the measurement. Typically, quantitative work was done with an overall count rate of about 3,000 cps for the entire spectrum. ![]() These had sealed, thin entrance windows that allowed the detection of oxygen, but the detectors and electronics did not allow for high count rates. Analysis used to be performed with so called Si(Li) style EDS detectors. Because EDS results are proportional to weight percent and since oxygen is a relatively light atom changes in atom percent of oxygen in a sample result in smaller weight percent changes raising the precision required of the measurement. ![]() It is a difficult measurement and EDS detectors have historically been not efficient at measuring soft x-rays. ![]() Historically, conventional wisdom surrounding SEM/EDS elemental analysis has it that quantitative estimates for oxygen in oxides cannot be reliably arrived at by direct measurement of the oxygen peak. ![]()
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