Microwave Spectroscopy as a Potential Tool for Color Grading Diamonds

Yossi Rabinowitz, Ariel Etinger, Asher Yahalom, Haim Cohen and Yosef Pinhasi
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Yossi Rabinowitz: Department of Electrical & Electronic Engineering, Ariel University, Ariel 40700, Israel
Ariel Etinger: Department of Electrical & Electronic Engineering, Ariel University, Ariel 40700, Israel
Asher Yahalom: Department of Electrical & Electronic Engineering, Ariel University, Ariel 40700, Israel
Haim Cohen: Department of Chemical Sciences, Ariel University, Ariel 40700, Israel
Yosef Pinhasi: Department of Electrical & Electronic Engineering, Ariel University, Ariel 40700, Israel

Energies, 2021, vol. 14, issue 12, 1-18

Abstract: A diamond’s color grading is a dominant property that determines its market value. Its color quality is dependent on the light transmittance through the diamond and is largely influenced by nitrogen contamination, which induces a yellow/brown tint within the diamond, as well as by structural defects in the crystal (in rare cases boron contamination results in a blue tint). Generally, spectroscopic instrumentation (in the infrared or UV–visible spectral range) is used in industry to measure polished and rough diamonds, but the results are not accurate enough for precise determination of color grade. Thus, new methods should be developed to determine the color grade of diamonds at longer wavelengths, such as microwave (MV). No difference exists between rough and polished diamonds regarding stray light when the MW frequency is used. Thus, several waveguides that cover a frequency range of 3.95–26.5 GHz, as well as suitable resonator mirrors, have been developed using transmission/reflection and resonator methods. A good correlation between the S 12 parameter and the nitrogen contamination content was found using the transmission/reflection method. It was concluded that electromagnetic property measurements of diamonds in the MW frequency range can be used to determine their nitrogen content and color grading. The MW technique results were in good agreement with those obtained from the infrared spectra of diamonds.

Keywords: spectroscopy; dielectric measurements for materials; measurement techniques; spectrum analysis (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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