A method for electron probe quantitative analysis of apatite with small beam spot

Abstract

The present application belongs to the technical field of chemical electron probe testing, and particularly relates to an electron probe quantitative analysis method for testing apatite with a small beam spot. The method comprises sample pretreatment, determination of elements, line series and a spectrometer crystal, determination of standard samples, determination of acceleration voltage, determination of an analysis beam current and a beam spot, determination of peak position counting time, monitoring of sample testing, and apatite sample testing. The present application can effectively analyze apatites of small particles such as broken apatite particles in meteorites and apatite particles in mineral inclusions. The present application compares test results under different acceleration voltages and analysis beam currents to ensure that the sample is not damaged during testing, and the optimal test conditions are obtained to ensure the correctness of the test results.

Description

Technical Field

[0001] This invention belongs to the field of chemical electron probe testing technology, and specifically relates to an electron probe quantitative analysis method for apatite using small spot testing. Background Technology

[0002] Currently, apatite is widely present in various types of rocks and extraterrestrial samples. Electron probe microanalysis (EPMA) is an important tool for in-situ micro-area analysis and one of the most convenient and effective methods for in-situ micro-area analysis of apatite.

[0003] Although electron probe microanalysis (EPMA) offers high spatial resolution with beam sizes as low as 1 μm, the unstable structure of apatite minerals necessitates the use of large beam sizes (10 μm) and low currents (5-10 nA) when testing apatite. However, existing methods are inadequate for accurately testing certain samples. For instance, many inclusions contain very small apatite particles, typically only a few micrometers in size, or the apatite in meteorite samples is fragmented. EPMA requires flat, crack-free samples, making it impossible to use large beam sizes for analysis. Small beam sizes are necessary, but existing methods using small beam sizes can easily damage the sample structure, causing F and Cl element migration and resulting in inaccurate data. Summary of the Invention

[0004] This invention proposes an electron probe quantitative analysis method for testing apatite using small spot patterns, which solves the problems of inaccurate test results and damage to the apatite sample structure when using small spot patterns to test apatite in the prior art.

[0005] The technical solution of this invention is implemented as follows: An electron probe microanalysis method for quantitative analysis of apatite using small spot assays includes the following steps: (1) Sample pretreatment; (2) Determine elements, line series and spectroscopic crystal; (3) Determine standard samples; (4) Determine accelerating voltage, which is 10-15kV; (5) Determine analytical beam current and beam spot, which is 1-2nA and 5μm; (6) Determine peak counting time; (7) Monitor sample Durango test; (8) Test apatite sample.

[0006] Optionally, the specific steps of sample pretreatment in step (1) are as follows: the sample is prepared into a probe sheet or sample target that can be loaded into the electron probe sample stage. After grinding, polishing, cleaning and drying, the sample surface is made smooth and clean. Then, the sample is treated with carbon spraying together with the standard sample to ensure that the carbon film thickness is consistent. The apatite particles to be analyzed are found by observing the backscattered image.

[0007] Optionally, the specific steps for determining the elements, line series, and spectroscopic crystal in step (2) are as follows: Since small spot analysis can easily lead to the destruction of the apatite structure, the main analytical elements are selected for testing, including F, Cl, Ca, Si, Na, P, and S. Based on the properties of their characteristic X-rays, line series with strong counting intensity, high peak-to-background ratio, and less interference are selected. The Kα line series is selected for all seven elements: F, Cl, Ca, Si, Na, P, and S. F is an ultralight element and a volatile unstable element, so artificially synthesized LDE1 crystal is used; PET crystal is used for Cl, Ca, P, and S; and TAP crystal is used for Na and Si.

[0008] Optionally, the specific steps for determining the standard samples in step (3) are as follows: according to the principle of similar matrix, F, Ca and P use apatite as standard samples, Si and Na use jadeite as standard samples, and Cl and S use sodium silicate aluminum aluminum ore and gypsum as standard samples respectively.

[0009] Optionally, the specific steps for determining the accelerating voltage in step (4) are as follows: For samples with insufficient test area, selecting an excessively high accelerating voltage will increase the excitation depth of the sample, leading to a decrease in spatial resolution and a risk of sample mixing for samples with limited test area. On the other hand, if the accelerating voltage is too low, the overvoltage ratio of the element will be insufficient, resulting in insufficient X-ray excitation and a decrease in the accuracy of the test results. Moreover, the apatite mineral structure is unstable, and the selection of the accelerating voltage must also take into account the stability of the F element, thus determining the optimal accelerating voltage as 10kV.

[0010] Optionally, the specific operation steps for determining the analytical beam current and beam spot in step (5) are as follows: After determining the accelerating voltage, it is necessary to determine the analytical beam current and beam spot to ensure that the sample is not damaged during the test, so as to ensure the accuracy of the sample test results. The optimal beam current is determined to be 2nA and the beam spot is 5μm.

[0011] Optionally, the specific steps for determining the peak counting time in step (6) are as follows: The length of the peak counting time directly affects the testing accuracy of the elements. The longer the time, the higher the accuracy. However, due to the unstable structure of the apatite sample, an excessively long counting time may damage the sample results, thereby affecting the accuracy of the test results. Moreover, an excessively long overall testing time will reduce the testing efficiency. Based on the element stability, testing accuracy and testing efficiency, this invention determines that the peak counting time for F, Ca and S is 60s; and the peak counting time for Na, Si, Cl and P is 30s.

[0012] Optionally, the specific operation steps for monitoring sample testing in step (7) are as follows: according to the experimental testing conditions determined in steps (2) to (6), the monitoring sample Durango is tested and compared with the recommended value to confirm that the testing method is effective and feasible.

[0013] Optionally, the specific operation steps for testing the apatite sample in step (8) are as follows: after confirming the effectiveness and feasibility of the method in step (7), the apatite sample to be tested is tested using the experimental test conditions determined in steps (2) to (6).

[0014] After adopting the above technical solution, the beneficial effects of the present invention are: This invention reduces the beam size for electron probe microanalysis of apatite from 10 μm in existing technologies to 5 μm, significantly improving the spatial resolution of the test and fully leveraging the advantages of high spatial resolution of electron probe microanalysis. It can effectively analyze fragmented apatite particles in meteorites and apatite particles within mineral inclusions.

[0015] This invention uses a Durango sample parallel to the C-axis as a monitoring sample to monitor the accuracy of test results for unstable elements F and Cl and major elements Ca and P, ensuring the effectiveness of testing in the most unstable direction and expanding the application range of the test conditions.

[0016] This invention minimizes damage to apatite samples by adjusting different accelerating voltages, analytical beam currents, and beam spots, thereby reducing the size of the analytical beam spot and improving spatial resolution without damaging the sample.

[0017] This invention uses the increased peak counting time to balance the decrease in data accuracy caused by the reduction in beam current, thus achieving both a smaller beam spot size and the assurance of accuracy and precision in the test results. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The backscattering pattern of the sample MGMH#128441A is shown. Figure 2 This is a 1:1 correspondence line between the Durango experimental results and the recommended values ​​in this embodiment of the invention; Figure 3 This is a 1:1 correspondence line between the experimental results of MGMH#128441A in this embodiment of the invention and the previous test results; Figure 4 The line showing the 1:1 correspondence between the experimental results of CaO and P2O5 in Comparative Examples 1, 2 and 5 of this invention and the recommended values; Figure 5The graphs show the detection limits of F, Cl, Ca, and P in Comparative Examples 1, 2, and 5 of this invention compared with those in Example 1. Figure 6 This is a comparison curve of the standard deviations of F, Cl, Ca, and P in Comparative Examples 1, 2, and 5 of the present invention with that in Example 1. Figure 7 The graph shows the F element test results of Durango in Comparative Examples 3, 4, 6 and 7 of this invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] according to Figures 1 to 7 As shown in the embodiments, this application discloses an electron probe quantitative analysis method for testing apatite using small spot patterns.

[0022] Example 1

[0023] An electron probe microanalysis method for quantitative analysis of apatite using small spot assays includes the following steps: (1) Sample pretreatment The monitoring sample Durango and the test sample MGMH#128441A were respectively coated with resin to form targets along a direction parallel to the C-axis. After grinding, polishing, cleaning, and drying to ensure that the surface of the samples was smooth and clean, carbon spraying was performed. The backscatter image of the test sample was then observed. Figure 1 As shown.

[0024] (2) Determine the elements, lineages, and spectroscopic crystals. Analytical elements for small-spot analysis of apatite were determined as small-spot analysis can easily damage the apatite structure. Therefore, only seven key elements were selected for testing: F, Cl, Ca, Si, Na, P, and S. Based on the properties of their characteristic X-rays, X-ray series with high counting intensity, high peak-to-background ratio, and low interference were chosen. Specifically, the Kα series was used for F, Cl, Ca, Si, Na, P, and S. As an ultralight and volatile unstable element, F was analyzed using synthetically produced LDE1 crystals; PET crystals were used for Cl, Ca, P, and S; and TAP crystals were used for Na and Si.

[0025] (3) Determine the standard sample Based on the principle of similar matrix, apatite was used as the standard for F, Ca, and P, jadeite was used as the standard for Si and Na, and sodium silicate aluminum silicate and gypsum were used as the standard for Cl and S, respectively.

[0026] (4) Determine the accelerating voltage Select an accelerating voltage of 10kV.

[0027] (5) Determine the analytical beam and beam spot The analysis beam spot size was selected as 5 μm, and the beam current was 2 nA.

[0028] (6) Determine the peak counting time The peak counting time for F, Ca, and S is 60 s; the peak counting time for Na, Si, Cl, and P is 30 s.

[0029] (7) Monitoring sample testing The Durango sample was tested using the experimental conditions determined in steps (2)-(6). The results are shown in Table 1.

[0030] Table 1. Average value of 10 tests conducted on Durango under the conditions of Example 1. Test element mass fraction (wt%) Recommended value (wt%) Limit of detection (ppm) Standard deviation (%) F 3.54 3.53 340.90 2.19 <![CDATA[Na2O]]> 0.27 0.23 304.00 20.57 <![CDATA[SiO2]]> 0.30 0.34 391.20 15.77 CaO 53.97 54.02 435.40 0.78 Cl 0.40 0.41 188.40 7.97 <![CDATA[P2O5]]> 40.62 40.78 534.90 1.30 <![CDATA[SO3]]> 0.32 0.37 343.50 15.83 Total 97.84 / / / Table 1 and Figure 2 The results of 10 tests for the main elements F, Cl, Ca, and P showed average values ​​of 3.54%, 0.4%, 53.97%, and 40.62%, respectively, while the recommended values ​​were 3.53%, 0.41%, 54.02%, and 40.78%, respectively. The results were consistent with the recommended values ​​within the error range, and both results fell on the 1:1 correspondence line, indicating that the testing method was effective and feasible.

[0031] (8) Apatite sample testing Using the experimental test conditions determined in steps (2)-(6), the test samples were tested, and the test results are shown in Table 2.

[0032] Table 2. Average value of 10 tests of MGMH#128441A under the conditions of Example 1 test element mass fraction (wt%) Previous test values ​​(wt%) Limit of detection (ppm) Standard deviation (%) F 2.17 2.15 342.60 3.04 <![CDATA[Na2O]]> 0.22 0.18 293.50 24.01 <![CDATA[SiO2]]> 0.53 0.52 403.60 10.29 CaO 53.51 53.47 436.80 0.78 Cl 1.02 0.99 186.40 4.43 <![CDATA[P2O5]]> 40.35 40.53 485.10 1.29 <![CDATA[SO3]]> 0.22 0.11 380.00 22.53 Total 96.89 / / / As shown in Table 2, the average contents of the main elements F, Cl, Ca, and P are 2.17%, 1.02%, 53.51%, and 40.35%, respectively. These figures are consistent with previous tests (data from Inter-laboratory Characterisation of Apatite Reference Materials for Chlorine Isotope Analysis), which yielded contents of 2.15%, 0.99%, 53.47%, and 40.53%, respectively. Figure 3 As shown, both results fall on the 1:1 correspondence line, indicating that the testing method is effective and feasible.

[0033] Example 2 In step (4), the test voltage is 15kV, and in step (5), the analysis beam current is 1nA and the beam spot is 5μm. Other steps are the same as in Example 1.

[0034] The monitoring sample Durango and the test sample MGMH#128441A were tested using the experimental test conditions determined in steps (2)-(6). The results are shown in Tables 3 and 4.

[0035] Table 3. Average results of 10 tests conducted on Durango under the conditions of Example 2. Test element mass fraction (wt%) Recommended value (wt%) Limit of detection (ppm) Standard deviation (%) F 3.39 3.53 508.10 3.43 <![CDATA[Na2O]]> 0.21 0.23 450.30 37.41 <![CDATA[SiO2]]> 0.26 0.34 372.40 17.77 CaO 53.53 54.02 325.30 0.68 Cl 0.40 0.41 176.20 7.69 <![CDATA[P2O5]]> 41.58 40.78 547.40 1.33 <![CDATA[SO3]]> 0.35 0.37 313.50 15.30 Total 98.21 / / / Table 4. Average value of 10 test results for MGMH#128441A under the conditions of Example 2 test element mass fraction (wt%) Previous test values ​​(wt%) Limit of detection (ppm) Standard deviation (%) F 2.14 2.15 519.50 4.76 <![CDATA[Na2O]]> 0.16 0.18 405.10 43.54 <![CDATA[SiO2]]> 0.52 0.52 371.30 10.56 CaO 53.54 53.47 332.30 0.69 Cl 1.04 0.99 172.90 4.33 <![CDATA[P2O5]]> 40.73 40.53 513.90 1.34 <![CDATA[SO3]]> 0.18 0.11 309.60 25.54 Total 97.17 / / / As shown in Tables 3 and 4, the average contents of the main elements F, Cl, Ca, and P in the monitored sample Durango were 3.39%, 0.40%, 53.53%, and 41.58%, respectively. The average contents of the main elements F, Cl, Ca, and P in the tested sample MGMH#128441A were 2.14%, 1.04%, 53.54%, and 40.73%, respectively. Although the relative error increased compared to Example 1, especially with a significant increase in the detection limit and standard deviation of the ultralight element F, and the accuracy of the F element was somewhat worse than in Example 1, the average values ​​of both sets of test results were consistent with the recommended values ​​or previous test results, and both results fell within a 1:1 correspondence line (see details). Figure 1 , Figure 2 ).

[0036] Example 3 In step (4), the test voltage is 12kV, and in step (5), the analysis beam current is 1.5nA and the beam spot is 5μm. Other steps are the same as in Example 1.

[0037] The monitoring sample Durango and the test sample MGMH#128441A were tested using the experimental test conditions determined in steps (2)-(6). The results are shown in Tables 5 and 6.

[0038] Table 5. Average results of 10 tests conducted on Durango under the conditions of Example 3. Test element mass fraction (wt%) Recommended value (wt%) Limit of detection (ppm) Standard deviation (%) F 3.51 3.53 379.40 2.57 <![CDATA[Na2O]]> 0.23 0.23 355.50 27.24 <![CDATA[SiO2]]> 0.32 0.34 423.50 20.07 CaO 53.73 54.02 359.90 0.71 Cl 0.39 0.41 173.40 7.83 <![CDATA[P2O5]]> 41.55 40.78 520.70 1.27 <![CDATA[SO3]]> 0.33 0.37 303.40 14.59 Total 98.49 / / / Table 6. Average value of 10 test results for MGMH#128441A under the conditions of Example 3. Test element mass fraction (wt%) Previous test values ​​(wt%) Limit of detection (ppm) Standard deviation (%) F 2.13 2.15 382.80 3.52 <![CDATA[Na2O]]> 0.15 0.18 365.30 39.24 <![CDATA[SiO2]]> 0.67 0.52 440.50 10.90 CaO 53.52 53.47 367.50 0.72 Cl 1.05 0.99 168.20 4.23 <![CDATA[P2O5]]> 41.55 40.53 510.70 1.28 <![CDATA[SO3]]> 0.20 0.11 299.80 21.09 Total 98.15 / / / As shown in Tables 5 and 6, the average contents of the main elements F, Cl, Ca, and P in the monitored sample Durango were 3.51%, 0.39%, 53.73%, and 41.55%, respectively. The average contents of the main elements F, Cl, Ca, and P in the tested sample MGMH#128441A were 2.13%, 1.05%, 53.52%, and 41.55%, respectively. Compared with Example 1, the detection limit and standard deviation of the ultralight element F were slightly increased, and the accuracy of F was somewhat worse than in Example 1. However, the average values ​​of both sets of test results were consistent with the recommended values ​​or previous test values, and both results fell within the 1:1 correspondence line (see details). Figure 1 , Figure 2 ).

[0039] Comparative Example 1 In step (4), the accelerating voltage was 5 kV, and in step (5), the analytical beam current was 2 nA and the beam spot size was 5 μm. The other steps were the same as in Example 1. The Durango sample was tested using the experimental conditions determined in steps (2)-(6). The results are shown in Table 7.

[0040] Table 7. Average results of 10 tests conducted on Durango under Comparative Example 1 conditions. Test element mass fraction (wt%) Recommended value (wt%) Limit of detection (ppm) Standard deviation (%) F 3.35 3.53 402.90 2.55 <![CDATA[Na2O]]> 0.26 0.23 638.50 35.16 <![CDATA[SiO2]]> 0.37 0.34 1270.90 52.22 CaO 43.79 54.02 5662.20 4.16 Cl 0.41 0.41 833.80 27.19 <![CDATA[P2O5]]> 40.70 40.78 2062.70 2.89 <![CDATA[SO3]]> 0.22 0.37 1547.70 102.11 Total 87.59 / / / It can be seen that due to the low voltage, the X-ray excitation is insufficient, as shown in Table 7. Figure 5 and Figure 6 It can be seen that the detection limits and standard deviations of F, Cl, Ca and P are all higher than those of Example 1. The detection limits increased by 18.19%, 342.57%, 1200.46% and 285.62%, respectively, and the standard deviations increased by 16.05%, 241.13%, 433.63% and 123.17%, respectively. Figure 4 It can be seen that the experimental results for CaO deviate significantly from the true value, with the total average value being only 87.59%, indicating that the test conditions are unusable.

[0041] Comparative Example 2 In step (4), the accelerating voltage was 10 kV, and in step (5), the analytical beam current was 0.5 nA and the beam spot size was 5 μm. The other steps were the same as in Example 1. The monitoring sample Durango was tested using the experimental test conditions determined in steps (2)-(6). The results are shown in Table 8.

[0042] Table 8. Average values ​​of 10 tests conducted on Durango under Comparative Example 2 conditions. Test element mass fraction (wt%) Recommended value (wt%) Limit of detection (ppm) Standard deviation (%) F 3.31 3.53 695.20 4.64 <![CDATA[Na2O]]> 0.23 0.23 828.10 72.22 <![CDATA[SiO2]]> 0.19 0.34 888.80 81.32 CaO 54.43 54.02 1206.30 1.56 Cl 0.42 0.41 485.20 17.98 <![CDATA[P2O5]]> 42.95 40.78 1728.90 2.59 <![CDATA[SO3]]> 0.37 0.37 1161.40 44.75 Total 100.40 / / / As can be seen from Table 8, due to the low analytical beam current, the detection limits of F, Cl, Ca, and P increased by 103.93%, 157.54%, 177.06%, and 223.22% respectively compared to Example 1, and the standard deviations increased by 111.72%, 125.63%, 100.13%, and 99.85% respectively. The testing accuracy of the data significantly decreased, and from... Figure 4 It can be seen that the average result of P2O5 deviates from the 1:1 comparison line, and the error increases, indicating that the test conditions are unusable.

[0043] Comparative Example 3 In step (4), the accelerating voltage was 20 kV, and in step (5), the analytical beam current was 2 nA and the beam spot size was 5 μm. The other steps were the same as in Example 1. The Durango sample was tested using the experimental conditions determined in steps (2)-(6). The results are shown in Table 9.

[0044] Table 9. Average results of 10 tests conducted on Durango under Comparative Example 3. Test element mass fraction (wt%) Recommended value (wt%) Limit of detection (ppm) Standard deviation (%) F 3.92 3.53 423.50 2.61 <![CDATA[Na2O]]> 0.23 0.23 264.30 21.40 <![CDATA[SiO2]]> 0.24 0.34 251.30 11.63 CaO 53.16 54.02 154.10 0.37 Cl 0.40 0.41 86.20 4.30 <![CDATA[P2O5]]> 40.50 40.78 257.20 0.80 <![CDATA[SO3]]> 0.35 0.37 130.10 7.61 Total 97.08 / / / It can be seen that while excessively high accelerating voltage reduces the detection limits and uncertainties of Ca, P, and Cl, thus improving data accuracy, it actually decreases the data accuracy for the unstable element F. Excessively high accelerating voltage leads to poor counting stability for F. Figure 7 As can be seen in (a), the F content of the 10 test results is generally higher than the recommended value of 3.53%, and the relative error of F also increases to 11.03%, thus affecting the overall data accuracy and indicating that the test conditions are unusable.

[0045] Comparative Example 4 In step (4), the accelerating voltage was 10 kV, and in step (5), the analytical beam current was 5 nA and the beam spot size was 5 μm. The other steps were the same as in Example 1. The Durango monitoring sample was tested using the experimental test conditions determined in steps (2)-(6). The results are shown in Table 10.

[0046] Table 10 Average results of 10 tests conducted on Durango under Comparative Example 4 Test element mass fraction (wt%) Recommended value (wt%) Limit of detection (ppm) Standard deviation (%) F 4.01 3.53 218.90 1.30 <![CDATA[Na2O]]> 0.28 0.23 179.90 11.80 <![CDATA[SiO2]]> 0.26 0.34 245.40 11.28 CaO 53.70 54.02 252.70 0.49 Cl 0.38 0.41 107.50 5.09 <![CDATA[P2O5]]> 40.89 40.78 264.70 0.81 <![CDATA[SO3]]> 0.35 0.37 171.30 8.50 Total 98.08 / / / As shown in Table 10, although the increased analytical beam current reduced the detection limits and uncertainties of the four main elements by 35.79%, 42.94%, 41.96%, and 50.51% respectively, and the standard deviations by 40.95%, 36.16%, 36.97%, and 37.30% respectively, significantly improving data accuracy, the increased beam current was detrimental to the unstable element F. Figure 7As can be seen from (b) in the table, the F content of the 10 test results is generally too high, all of which are above the recommended value of 3.53%. The relative error of F also increased to 13.69%, which affected the overall data accuracy and indicated that the test conditions were not usable.

[0047] Comparative Example 5 In step (4), the accelerating voltage was 5 kV, and in step (5), the analytical beam current was 0.5 nA and the beam spot size was 5 μm. The other steps were the same as in Example 1. The Durango sample was tested using the experimental conditions determined in steps (2)-(6). The results are shown in Table 9.

[0048] Table 11 Average results of 10 tests conducted on Durango under Comparative Example 5 Test element mass fraction (wt%) Recommended value (wt%) Limit of detection (ppm) Standard deviation (%) F 3.22 3.53 776.00 5.19 <![CDATA[Na2O]]> 0.26 0.23 1786.00 124.32 <![CDATA[SiO2]]> 0.26 0.34 2926.50 90.20 CaO 46.31 54.02 19640.00 8.84 Cl 0.41 0.41 2800.30 130.85 <![CDATA[P2O5]]> 40.70 40.78 7781.10 6.03 <![CDATA[SO3]]> 0.26 0.37 5800.20 258.79 Total 89.96 / / / It can be seen that due to the low voltage, the X-ray excitation was insufficient, and the analytical beam current was too low, causing the detection limits and standard deviations of F, Cl, Ca, and P to increase sharply. Figure 5 , Figure 6 The limits of detection increased by 127.63%, 1386.36%, 4410.79%, and 1354.68%, respectively, and the standard deviations increased by 136.48%, 1541.76%, 1034.66%, and 365.56%, respectively. Figure 4 It can be seen that the experimental results for CaO deviate significantly from the true value, with an average total amount of only 89.96%, indicating that the test conditions are unusable.

[0049] Comparative Example 6 In step (4), the accelerating voltage was 20 kV, and in step (5), the analytical beam current was 5 nA and the beam spot size was 5 μm. The other steps were the same as in Example 1. Tests were performed on the monitoring sample, and the test results are shown in Table 12.

[0050] Table 12 Average results of 10 tests conducted on Durango under Comparative Example 6 conditions Test element mass fraction (wt%) Recommended value (wt%) Limit of detection (ppm) Standard deviation (%) F 4.35 3.53 276.90 1.55 <![CDATA[Na2O]]> 0.27 0.23 157.90 11.80 <![CDATA[SiO2]]> 0.25 0.34 159.60 7.23 CaO 53.54 54.02 92.90 0.24 Cl 0.45 0.41 53.10 2.52 <![CDATA[P2O5]]> 40.53 40.78 148.20 0.50 <![CDATA[SO3]]> 0.42 0.37 73.80 4.04 Total 97.87 / / / It can be seen that the increased accelerating voltage and analytical beam current significantly reduce the detection limits and uncertainties of Cl, Ca, and P, resulting in a marked improvement in data accuracy. The detection limits are reduced by 71.82%, 78.66%, and 72.29% respectively compared to Example 1, and the standard deviations are reduced by 68.43%, 69.19%, and 61.24% respectively. However, for the unstable element F, although the data accuracy also decreases, with the detection limit and uncertainty decreasing by 18.77% and 29.14% respectively, excessively high accelerating voltage and analytical beam current can lead to poor counting stability of F, causing element migration. Figure 7As can be seen from (c), the average F content of the 10 test results was 4.35%, which was significantly higher than the recommended value of 3.53%. The relative error of F increased to 23.29%, indicating that the accuracy of F was extremely poor and that the test conditions were unusable.

[0051] Comparative Example 7 In step (4), the accelerating voltage was 10 kV, and in step (5), the analytical beam current was 2 nA and the beam spot size was 2 μm. The other steps were the same as in Example 1. Tests were performed on the monitoring sample, and the test results are shown in Table 13.

[0052] Table 13 Average results of 10 tests conducted on Durango under the conditions of Comparative Example 7 Test element mass fraction (wt%) Recommended value (wt%) Limit of detection (ppm) Standard deviation (%) F 3.76 3.53 334.20 2.10 <![CDATA[Na2O]]> 0.26 0.23 316.90 20.63 <![CDATA[SiO2]]> 0.23 0.34 399.90 20.23 CaO 54.49 54.02 440.00 0.78 Cl 0.35 0.41 187.70 12.60 <![CDATA[P2O5]]> 41.97 40.78 527.80 1.27 <![CDATA[SO3]]> 0.24 0.37 318.60 18.83 Total 99.64 / / / It can be seen that because the analytical beam current remains constant, the accuracy of the tested elements remains essentially unchanged. However, the accuracy of the F and Cl data deviates significantly from the recommended values. This is mainly due to the reduced beam spot size and unstable element counting, leading to a decrease in accuracy. Figure 7 As can be seen from (d) in the data, the overall F content of the 10 test results is higher than the recommended value by 3.53%, and the relative error of F also increases to 6.41%, thus affecting the overall data accuracy. Since Durango contains a certain amount of rare earth elements, the average total of 99.4% is also significantly high, indicating that the test conditions are unusable.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for quantitative analysis of apatite using electron probe microanalysis with small spot size testing, characterized in that, The test conditions for testing apatite using a small beam spot are: accelerating voltage of 10-15kV, beam current of 1-2nA, and beam spot size of 5μm.

2. The electron probe microanalysis method for small-spot testing of apatite according to claim 1, characterized in that, The testing conditions also include sample pretreatment, the specific procedures of which are as follows: The monitoring sample and the apatite sample were separately coated with resin to prepare targets. After grinding, polishing, cleaning and drying to ensure that the sample surface was flat and clean, carbon spraying was performed. The apatite particles to be analyzed were found by observing backscattered images.

3. The electron probe quantitative analysis method for small-spot testing of apatite according to claim 1, characterized in that, The testing conditions also included determining the elements, line series, and spectroscopic crystals. The seven elements were determined to be F, Cl, Ca, Si, Na, P, and S. The Kα line series was selected for all seven elements. F, as an ultralight element and a volatile and unstable element, was produced using artificially synthesized LDE1 crystals. PET crystals were used for Cl, Ca, P, and S, while TAP crystals were used for Na and Si.

4. The electron probe microanalysis method for small-spot testing of apatite according to claim 1, characterized in that, The testing conditions also include determining the standard sample, and the specific procedures are as follows: Based on the principle of similar matrix, apatite was used as the standard for F, Ca, and P, jadeite was used as the standard for Si and Na, and sodium silicate aluminum silicate and gypsum were used as the standard for Cl and S, respectively.

5. The electron probe quantitative analysis method for small-spot testing of apatite according to claim 1, characterized in that, The accelerating voltage is 10kV.

6. The electron probe quantitative analysis method for small-spot testing of apatite according to claim 1, characterized in that, The beam current is 2nA.

7. The electron probe quantitative analysis method for small-spot testing of apatite according to claim 1, characterized in that, The test conditions also include determining the peak counting time: 60s for F, Ca, and S; and 30s for Na, Si, Cl, and P.

8. The electron probe quantitative analysis method for small-spot testing of apatite according to claim 1, characterized in that, The testing conditions also include monitoring sample testing, using a Durango sample parallel to the C-axis as the monitoring sample.

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