Type Ib Yellow to Brownish Yellow CVD Synthetic Diamond

Abstract

Fifteen CVD synthetic diamonds in yellow hues submitted for grading without disclosure were tested in this study. They were proved to be type Ib containing isolated substitutional nitrogen 3.6 ppm on average. From the microscopic observation, the presence of H3 and N3, the H3/NV^- intensity ratio and the absorption peaks due to C-H related defects that were detected in infrared spectral analysis, these stones can be assumed to have undergone annealing about 1900-2200°:C (supposedly HPHT treatment) after the growth.