Cathodoluminescence of synthetic diamonds annealed at high temperature without stabilizing pressure

Nitrogen-containing synthetic diamonds heated at temperatures 1800, 2000 and 2500°C in hydrogen atmosphere (LPHT annealing) have been studied by cathodoluminescence (CL). After LPHT annealing, the transformations of nickel and nitrogen related defects were found similar to those occurred after annealing under high stabilizing pressure (HPHT annealing). An assumption is made that LPHT annealing may remove yellow color of synthetic HPHT-grown diamonds in areas where nickel and nitrogen have “matching” concentrations. The areas with excessive concentration of nickel, or nitrogen remain yellow even after 48h LPHT annealing at temperature 1800°C. [Display omitted] •LPHT annealing is effective in aggregation of nitrogen into A-defects.•Sole LPHT annealing is not effective in aggregation of nitrogen into B-defects.•Discoloration of synthetic diamonds occurs for “matching” concentrations of Ni and N.