Microwave spectroscopy as a potential tool for characterizing synthetic HPHT diamonds

Abstract

A major criterion for diamond grading is its origin: is it a natural or synthetic diamond? One of the main techniques used for manufacturing synthetic diamonds is the HPHT (high pressure high temperature) process. The HPHT method produces diamonds that have the same structure as natural diamonds; thus, there is a need in gemological laboratories to determine whether the diamond is natural or produced via the HPHT method. A new analysis procedure based on microwave (MW) spectroscopy is proposed. Using the transmission/reflection method (TRM), we determine whether a diamond is natural or manufactured artificially via HPHT. Several waveguides, which cover the 12–26 GHz frequency range, were developed. A good correlation between the S₁₂ parameter and the origin of the diamond was obtained. The results in the spectral range of 12–12.7 GHz, 20.9–21 GHz, and 22.2–22.23 GHz suggest that this is an efficient method for determining whether a diamond is HPHT produced or it is a natural diamond.