Example Data Table
This sample uses common SEM cation atomic percentages for a silicate-rich material.
| Oxide |
Cation |
Atomic % Input |
Common Use |
| SiO2 | Si | 42.50 | Silicate framework |
| Al2O3 | Al | 10.20 | Aluminosilicate phase |
| Fe2O3 | Fe | 4.10 | Ferric iron reporting |
| MgO | Mg | 8.80 | Magnesium component |
| CaO | Ca | 12.40 | Calcium component |
| Na2O | Na | 3.30 | Sodium component |
| K2O | K | 1.70 | Potassium component |
| TiO2 | Ti | 0.90 | Titanium component |
Formula Used
The calculator converts cation atomic percentages into oxide mass units.
Each oxide formula has a fixed molar mass and cation count.
Conversion factor = oxide molar mass / number of cations in oxide formula
Raw oxide mass units = cation atomic % × conversion factor
Normalized oxide % = raw oxide mass units / total raw oxide mass units × target total
Example for SiO2:
SiO2 has one Si atom.
Its molar mass is 60.0843.
The factor is 60.0843 / 1.
A Si atomic value of 42.50 gives 2553.58275 raw units.
Atomic Percent to Oxide Percent in SEM Reports
Why This Conversion Matters
SEM and EDS software often reports elements as atomic percent.
Many geology, ceramic, glass, cement, and materials reports use oxide percent instead.
The two values are not the same.
Atomic percent counts atoms.
Oxide percent estimates the mass share of a chosen oxide formula.
This calculator connects those two reporting styles with a clear normalization step.
Understanding the Input
Enter only the cation atomic percent for each oxide.
For example, enter Si when reporting SiO2.
Enter Al when reporting Al2O3.
Do not enter oxygen as a separate cation row.
The oxygen amount is already included through the oxide formula.
This keeps the conversion consistent.
It also avoids double counting oxygen in the final oxide total.
How Oxide Factors Work
Every oxide has a molar mass.
Every oxide also has a fixed number of cations.
SiO2 has one silicon atom.
Al2O3 has two aluminum atoms.
Na2O has two sodium atoms.
The calculator divides oxide molar mass by the number of cations.
That value becomes the conversion factor.
The atomic percent is multiplied by this factor.
The result is a raw oxide mass unit.
Why Normalization Is Needed
Raw oxide mass units do not usually total exactly 100.
They are relative values.
Normalization scales every oxide by the same proportion.
The final total becomes the selected target total.
Most reports use 100 percent.
Some special workflows may use another target total.
This can help compare prepared datasets or corrected totals.
SEM and Practical Accuracy
SEM data can be affected by coating, roughness, standards, beam settings, and peak overlaps.
Light elements can be difficult to measure.
Low concentration elements can also have larger uncertainty.
Use this calculator as a reporting and conversion tool.
It does not replace instrument calibration or expert interpretation.
Always review your SEM method and sample preparation.
Choosing Oxide Forms
Some elements can be reported in more than one oxide form.
Iron is a common example.
It may be reported as FeO or Fe2O3.
The correct choice depends on the material, convention, and lab method.
Choose the oxide form that matches your report standard.
Keep that choice consistent across related samples.
Using the Results
The result table shows the selected oxide, input cation value, conversion factor, raw mass units, and normalized oxide percent.
The CSV export is useful for spreadsheets.
The PDF export is useful for quick documentation.
Keep the exported file with the original SEM spectrum when traceability is important.
This makes later review easier and clearer.
FAQs
1. What does atomic percent mean in SEM?
Atomic percent shows the relative number of atoms detected for each element. It is not a direct mass percentage.
2. What does oxide percent mean?
Oxide percent estimates how much mass would be present if each element were reported as a selected oxide formula.
3. Should I enter oxygen atomic percent?
No. Enter only cation atomic percent values. Oxygen is included automatically through each oxide formula.
4. Why does the calculator normalize results?
Raw oxide mass units rarely total exactly 100. Normalization scales every oxide so the report total matches your selected target.
5. Which iron oxide should I choose?
Choose FeO or Fe2O3 based on your lab convention, sample chemistry, or reporting standard. The choice changes the oxide percent.
6. Can I use this for EDS results?
Yes. It is suitable for SEM or EDS cation atomic percent tables when oxide reporting is required.
7. Does this correct SEM measurement errors?
No. It converts reported values only. It does not correct calibration, coating, surface, or spectral overlap issues.
8. Why are cations important?
The oxide formula may contain one or more cations. The calculator uses that cation count to calculate the correct oxide factor.
9. Can I add duplicate oxide rows?
Yes. Duplicate oxide rows are grouped together. Their atomic values and raw mass units are combined before normalization.
10. What target total should I use?
Use 100 for normal reporting. Use another target only when your lab method or correction workflow requires it.
11. Why does Na2O use two cations?
Na2O contains two sodium atoms per oxide formula unit. The molar mass is divided by two for the sodium conversion factor.
12. Can this calculator handle trace elements?
Yes. Enter small atomic percentages with enough decimal places. Review uncertainty when values are near detection limits.
13. Is the PDF export based on the result table?
Yes. The PDF button exports the visible result table after calculation. Calculate first for the best export.
14. Is oxide percent the same as weight percent?
Oxide percent is a normalized mass-based value for selected oxide formulas. It is commonly reported like oxide weight percent.