Automated FTIR mapping of boron distribution in diamond

Abstract TypeIIb diamonds are those that contain more boronthan nitrogen. The presence of this uncompensated borongives rise to absorption in the infrared part of the electromagnetic spectrum, extending into the visible region and often resulting in blue colouration. Here we report on the expansion of the DiaMap freeware (for the automated spectral deconvolution of Type I [nitrogen containing] diamonds) to work on Type IIb diamonds, returning concentrations from three boron-related absorption bands, and determining which band provides the most reliable value. The program uses the calibration coefficients of Collins (2010), which show good relative agreement between the three bands, but might require some further study to confirm their absolute accuracy to the uncompensated boronconcentration. The methodology of DiaMap_IIb is applicable to all Type IIb diamonds, both natural and synthetic. Analysis of high-resolution Fourier-transform infrared (FTIR) maps of two high-pressure high-temperature (HPHT) synthetic diamondsusing DiaMap_IIb, confirm the growth sector dependence of the boronincorporation. Partitioning of boronstrongly favours the octahedral {111} sectors.