Introduction

Initiated and Organized by the IUCr Commission on Powder Diffraction

Aims of the Round Robin

The round robin will focus on the analysis of powder diffraction data specifically for the derivation of quantitative phase abundance. While the study will focus on the use of laboratory X-ray, synchrotron X-ray and neutron diffraction data, other methods may be used to validate the diffraction results (e.g. FTIR, normative analysis, etc.). The additional methods used will be at the discretion of the participant.

General aims

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

• To document the methods & strategies commonly employed in Quantitative Phase Analysis (QPA), especially those involving powder diffraction
• To assess (i) levels of accuracy & precision, and (ii) lower limits of detection
• 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

Specific aims

The round robin will address the following analytical issues:

• Type of analysis:
  • diffraction (X-ray /Neutron) vs non-diffraction internal std vs external std vs spiking etc standardless methods
• Sample features
  • representivity & homogeneity
  • particle & crystallite size
  • statistics & microabsorption
  • crystallinity & surface roughness
  • preferred orientation, microabsorption & extinction
• Data collection
  • type of instrument / geometry
  • sample preparation
  • data range and wavelength
• Data analysis
  • integrated intensities vs full-profile Rietveld vs data-base of observed patterns
  • use of constraints and corrections
  • software systems & methods
  • complexity of the pattern - peak overlap

Possible levels of participation will include the following:

Diffraction data only

Participant analyses 'standard' data sets supplied by the CPD and returns details of the analytical procedure plus the results.

Get the Standard Powder X-ray Diffraction Data Sets via the web

Prepared samples

Participant collects own data for analysis from at least two of the samples supplied by the CPD ('simple' and 'preferred orientation')

Unprepared samples

Samples supplied by the CPD are representative of bulk, but may need additional preparation. Participant prepares samples for data collection and analysis.

Since the purpose of the round robin is to assess the methods of quantification, and not identification, the identity of each of the component phases will be supplied. For those participants using Rietveld based methods for the analysis, full structural information for each of the phases will also be supplied. Participants will be asked to return the results using 'standard' reporting forms. This should minimize the number of errors likely to occur during transcription of the data. In addition, it is requested that the diffraction data be returned to the CPD as an ASCII format file for re-analysis with a 'standard' Rietveld code.

Timeline - Initial Round of Samples went out in Early Jan 1998

The following timeline for the round robin is proposed:

August / September 1996

Final recommendations for mixtures and protocol Formal approval from CPD

August 96 - March 97

Call for expressions of interest

Samples sourced & prepared for distribution

Collection of standard data

Questionnaire sent to all participants

June 97

Samples and data distributed to participants

December 97

Call-in of results

January - June 98

Analysis of results (including late submissions)

August 98

Preliminary results presented at EPDIC-6

August 99

Presentation of final results at Glasgow IUCr Congress

How to participate

After deciding what you would like to analyse, contact us by email or any method you prefer. Details should include Name, Affiliation, Postal address, Phone and FAX numbers (including country and area codes), Email address. Extra information should include information about which of the samples you wish to analyze plus the amount of sample required (i.e. are they an X-ray, neutron user, XRF, IR, Wet Chemical, etc).

Operating Team

• Ian Madsen - CSIRO Minerals, Australia
• Rod Hill - CSIRO Minerals, Australia
• Edward Groleau - Eli Lilly & Co, USA
• Lachlan Cranswick - Melbourne, Australia (Now Daresbury Lab - U.K.)

Advisory Team

• Deane Smith (CPD) - Penn State University, USA
• Jaroslav Fiala - Central Res. Inst., Czech Rep.

Contact Details for all Correspondence

Get the Standard Powder X-ray Diffraction Data Sets via the web