Deriving the bulk modulus of a single-phase powder from the March preferred orientation parameter

This study has examined the validity of the March model using extensive suites of uniaxially pressed powders of molybdite and calcite neutron powder diffraction data, for which the compression was systematically varied. It is clear from the various Rietveld refinements that the model becomes increasingly unsatisfactory as the uniaxially applied compaction pressure (and, therefore, the level of preferred orientation) increase. The model has been tested with a physical relationship which links the March r-parameter to the compaction pressure via the powder bulk modulus, B. The agreement between the results obtained from directly measured values of B and from Rietveld analysis with the March model is promising in terms of deducing the powder bulk modulus from the March r-parameter