GB/T 36129-2018Gems testing—Cathode luminescence image method (English PDF)

1 Scope

This Standard specifies the method principle, test method and result representation of cathode luminescence image method for gems testing.

This Standard applies to the testing of gems and their optimizing processed products.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition dated applies to this document. For undated references, the latest edition of the referenced documents (including all amendments) applies to this document.

GB/T 16552, Gems - Nomenclature

GB/T 16553, Gems - Testing

GB/T 17359, Microbeam analysis - Quantitative analysis using energy dispersive spectrometry

3 Terms and definitions

For the purposes of this document, the following terms and definitions and those given in GB/T 16552 and GB/T 16553, apply.

4 Method principle

Gems of different kinds or gems of the same kinds from different origins can generate luminescence of different wavelengths and intensities under the bombardment of high-power electron beams. The colour and distribution characteristics of the luminescence can use used to determine the kinds and contents of some microelements in gems as well as their structural defects. Based on the characteristics such as the crystal structures or growing textures displayed by cathode luminescence images, the information can be known such as the growing environment, growing history, etc. of gems.

5 Cathodoluminescence process

The cathodoluminescence process of gems include.

a) that energy absorption cause the transition of electrons between valence bands and conduction bands as well as additional energy levels, transiting electrons to the excited state;

b) the residence time of electrons in the excited state is about 10^-9 s ~ 10^-7 s;

c) electrons in the excited state transits to the ground state through radiation to generate photon emission (luminescence).

6 Major factors influencing cathode luminescence

The major factors influencing cathode include.

a) activating agent. the content, kind and valence state of activating agent, the differences in solid materials attached, etc. influence the colours and intensities of cathode luminescence;

b) structural defects (or self-activation). structural defects and internal stresses

8 Test method

9 Representation of results

9.1 Describe the peculiar colours and structural characteristics observed under cathode luminescence, especially significant characteristics for testing.

a) colour description Directly use spectrum colours constituting visible light and their secondary colours as well as white, black and colourlessness to describe. Essential colours are in front and secondary colours are in the rear, e.g.. yellow green, green yellow. If necessary, add the descriptions of shade and intensity in front of colours, e.g.. light yellow green, dark green.

b) structure description In accordance with the luminescence and its distribution characteristics, describe the growing structure, automorphic degree, granular size, shape, inter relations between grains and between grains and matrixes, etc. of minerals constituting gems.

9.2 In accordance with the cathode luminescence characteristics, determine the nature […]