GB/T 37131-2018 in English

GB/T 37131—2018 Standard Overview

National Standard of the People's Republic of China GB/T 37131—2018 is called "Test Method for Ultraviolet-Visible Diffuse Reflectance Spectroscopy of Nanotechnology Semiconductor Nanopowder Materials", which mainly specifies the test method for diffuse reflectance spectroscopy of semiconductor nanopowder materials in the ultraviolet-visible band. This standard was proposed by the Chinese Academy of Sciences and is applicable to the characterization of optical properties of opaque semiconductor nanopowder materials.

---

Standard Formulation Background and Technology Evolution Analysis

With the rapid development of nanotechnology, semiconductor nanopowder materials have been widely used in new energy, environmental protection, chemical industry and other fields due to their unique optical and electrical properties. However, the performance characterization method is still imperfect, especially the standardization of ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) test method is urgently needed. This standard provides a scientific basis for the calculation of the band gap width of semiconductor nanopowder materials by combining the Kubelka-Munk equation with experimental data.

---

Test Principle and Core Parameters

1. Test Principle

The absorption characteristics of semiconductor nanopowder materials in the UV-visible band are closely related to their band gap width. By measuring the diffuse reflectance spectrum and combining it with the Kubelka-Munk equation, the band gap width of the material can be calculated.

Where $R_{\infty}$ represents the reflectivity of an infinitely thick sample, $K$ and $S$ are the absorption coefficient and scattering coefficient, respectively.

---

2. Key parameters

Parameter name	Definition and function	Test conditions
UV-Visible spectrophotometer	Used to measure the reflectance characteristics of the sample in the UV-Vis band.	Wavelength range: 200nm~800nm; slit width: 2nm~5nm.
Integrating sphere	Used to collect the diffuse reflected light of the sample and eliminate the polarization effect and inhomogeneity error.	The inner wall is coated with high reflectivity materials (such as Al₂O₃, BaSO₄, etc.).
Reference white board	Used to establish the system baseline to ensure the accuracy of the test results.	The surface is flat and smooth with high reflectivity.

---

Test method and steps

1. Sample preparation: Ensure that the sample is dry and fully powdered, and the amount used is not less than 20mg.
2. Instrument calibration: Calibrate the equipment according to the requirements of JJF 1232 and JG 178.
3. Test steps:
   1. Set the test parameters (wavelength range, scanning step, slit width, etc.).
   2. Use the reference white board to establish the baseline.
   3. Place the sample and perform UV-Vis diffuse reflectance spectrum scan.
   4. Repeat the test at least 3 times to ensure the reliability of the data.

---

Data Analysis and Result Processing

Extract the characteristic absorption wavelength and its corresponding reflectivity from the diffuse reflectance spectrum, and calculate the band gap width using formula (2):

Where, $E_g$ represents the band gap width, $A$ and $n$ are constants related to the material properties (n=1/2 for direct band gap semiconductors and n=2 for indirect band gap semiconductors).

---

Implementation Recommendations

• Sample Preparation: Ensure that the sample is fully dried and evenly dispersed to avoid agglomeration and impurities.
• Instrument calibration: Regularly calibrate the UV-Vis spectrophotometer and integrating sphere to ensure measurement accuracy.
• Test condition optimization: Adjust the scanning step length and slit width according to the sample characteristics. It is recommended to give priority to a medium slit width (2nm~5nm) to balance noise and resolution.
• Data processing: Analyze the test data using the methods provided in Appendix A and B, and verify with references [8]-[10].