I. Madsen

PRELIMINARY OUTCOMES OF THE IUCR CPD ROUND ROBIN ON QUANTITATIVE PHASE ANALYSIS

Ian Madsen

CSIRO Minerals, Box 312, Clayton South 3169, Victoria, Australia

The International Union for Crystallography - Commission on Powder Diffraction is currently sponsoring a round robin on quantitative phase analysis (QPA). The round robin is focusing on the analysis of powder diffraction data, namely laboratory X-ray, synchrotron X-ray and neutron diffraction data for the derivation of phase abundances.

The general goals of the round robin include the following:-

To document the methods & strategies commonly employed in quantitative phase analysis, especially those involving powder diffraction.
To assess (i) levels of accuracy & precision, and (ii) lower limits of detection of methods used in QPA.
To identify specific problem areas & develop practical solutions.
To formulate recommended procedures for QPA using diffraction data.
To create a standard set of samples for future reference.

The samples used in the study consist of mixtures of major and minor components covering a wide range of analytical complexity. Initial samples are synthetic mixtures of crystallographically 'simple' materials and should present little problem to the analyst. Additional samples introduce problems such as preferred orientation, microabsorption and amorphous content to assess the degree to which these problems affect QPA. Several very complex materials have also been included in the sample suite including a natural granodiorite, synthetic bauxite and a mixture of pharmaceutical phases. These last three samples represent a significant an analytical challenge as they exhibit preferred orientation, microabsorption and grain size effects in addition to severe peak overlap.

The round robin was tailored to allow variation in the level of participation including (i) analysis of 'standard' data sets supplied by the CPD, (ii) collection and analysis of data from at least two of the samples supplied by the CPD and (iii) selection of additional samples at the discretion of the participant.

At the time of writing this abstract, some 130 sets of samples had been sent out to participants with occasional requests still being received. Participants were asked to return the results of the first sample (a synthetic mixture of Al₂O₃, ZnO and CaF₂) by July 1998 with the results for the remaining samples due later in 1998. This presentation will include some details of the experimental design along with a preliminary report on the outcomes.