A correlation between the infrared absorption features and the low temperature thermal conductivity of different types of natural diamonds

The low-temperature thermal conductivity of three different types of natural diamond has been measured between 0.5 and 20K. It has been attempted to relate the infrared absorption features of the diamonds with their thermal conductivity. A diamond with only B features (i.e. no B' peak) in the infrared was found to contain aggregates with a mean diameter of about 44-65 AA and to have a concentration of about 10 14 aggregates per cm 3 from a fit of the conductivity curve. Electron microscope pictures showed aggregates of about 50 AA diameter with this concentration. These results tend to confirm a recent suggestion made by T.Evans, that the B features are due to larger (rather than very small) nitrogen aggregates.