Three physical quantities: There are three physical quantities that can be directly obtained from the diffraction spectrum, namely the diffraction peak position (2) θ)、 Diffraction peak intensity (I) and diffraction peak shape (f (x)). Any problem that powder diffraction can solve or any structural parameter that can be obtained is generally based on these three physical quantities.

Main technical parameters: A good instrument should be able to obtain accurate (measured values match their true values) and accurate (measurement repeatability is good) 2 θ、 I and f (x) need to consider the following main technical parameters:

1. The stability of the X-ray generator: This is not only related to the accuracy and reliability of the measured diffraction intensity, but also to the accuracy and stability of all components. The stability of the light source in modern powder diffractometer is generally within 10% of the external power supply change and 0.01% of the output change.

2. The power of X-ray tubes: For sealed X-ray tubes, Cu targets are generally 2kw, Ag, Mo, W targets are generally greater than 2kw, while for Co, Fe, Ni targets, it is less than 2kw. For target transfer, commonly used are 12kw and 18kw.

3. The efficiency of a monochromator should not be less than 25%.

4. The efficiency of detectors varies depending on the variety.

5. The linear range of counting is related to the accuracy of intensity measurement, usually in CPS. Many instruments have attached calibration software, claiming to achieve CPS.

6. Diffraction angle (2 θ) Measurement accuracy and precision.

7. Resolution: Commonly represented by the half width of the Si (311) diffraction peak. For a general laboratory powder diffractometer, this value is approximately 0.05&deg~ 0.1° Between.