Ian Madsen Letter (modified by Lachlan 17th Jan 1998) to Participants - Re analysing Standard Datasets

If you wish to run and analyse the powder samples (not just the standard datasets), contact us at qpa.rr@minerals.csiro.au (closing date April 5th 1998). Due to the popularity of the round robin, we have been running low on several of the mandatory samples.

Dear Colleagues,

At last, please find standard datasets for the Round Robin on quantitative phase analysis sponsored by the International Union for Crystallography - Commission on Powder Diffraction. The response to the call for expressions of interest has been very gratifying with powder samples being sent to some 110 people in the first mailing. The participants are predominantly X-ray diffraction users with about 10 participants indicating that they have access to neutron diffraction facilities.

My apologies for the lateness of the delivery of the samples, but we have encountered many problems in the selection of phases. In addition, the task of mixing, verification of the samples and packaging has been a larger task than any of us anticipated.

All that aside, in this web/internet package/kit you should find:-

1. Weblinks connecting to:-
   • The sets of 'standard' data (CPD-xx.DAT, where xx = the sample number) to be analysed by participants. In addition, a data set from Y₂O₃ (CPD-Y2O3.DAT) has been added for those participants who need to determine the instrumental peak widths. This file can be ignored in the majority of cases.
   • A text file (STRUCT.TXT) containing structural information for each of the phases.
   • A text file (CPD-DATA.RES) for the reporting of the results of analysis of the CPD supplied data. This is to be completed by the participants and returned to the organisers.

Following are some details of the work program required for participation in the round robin. The amount of work should not be too onerous and I look forward to receiving your results - please take note of the deadlines.

Files can be returned to Ian Madsen by (i) copying to a 3.5" floppy disc and mailing to the address at the end of this document, or (ii) attaching the files to an Email message and sending to qpa.rr@minerals.csiro.au

Once again my thanks to you for agreeing to participate in the round robin.

Regards

Ian C. Madsen (for the organising committee)

General

The round robin focuses on the analysis of powder diffraction data specifically for the derivation of quantitative phase abundance. While the study emphasises the use of laboratory X-ray, synchrotron X-ray and neutron diffraction data, other methods may be used at the discretion of the participant.

The goals of the round robin 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 in QPA and to develop practical solutions.
• To formulate recommended procedures for QPA using diffraction data.
• To create a standard set of samples for future reference.

Due to difficulties in obtaining some of the phases specified in the first announcement, the composition of some of the samples has been changed. This means that the samples no longer contain the ambiguity of chemistry included in the original design. Therefore, it is possible to obtain the phase abundances using conventional chemical analysis methods. However, we request that participants only analyse the samples using a single method (i.e. diffraction or XRF or ICP etc...) and not to verify their results using additional methods. This will provide the scientific community with a more realistic assessment of the levels of accuracy and precision which can be attained using diffraction methods.

Types of analyses

The involvement of participants in the round robin can vary depending on the amount of time available to each individual/laboratory. However, since the success of the round robin will depend on the number of results returned, full participation is encouraged.

Possible levels of participation will include the following:-

Material supplied by CPD	Participant actions
Diffraction data only	Participant analyses 'standard' data sets supplied by the CPD and returns details of the analytical procedure plus the results.
Prepared samples	Participant collects own data for analysis from at least three of the samples supplied by the CPD ('simple', 'preferred orientation', and 'crystallinity')
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 is supplied. For those participants using Rietveld based methods for the analysis, full structural information for each of the phases is also supplied.

Time-frame

Participants are requested to return the results for Sample #1 by 1st July 1998 and for the remaining samples by 1st October 1998.

It is proposed that preliminary findings of the round robin are to be presented at either the EPDIC-6 or ECM-18 meetings in August of 1998. Final outcomes will then be presented at the 18th Congress of the IUCr in Glasgow in August 1999.

What you need to do

The tasks you need to perform will depend on the level of involvement that you indicated on the questionnaire circulated last year. These will include:-

1. The analysis of the CPD supplied X-ray diffraction data.
2. Additional sample preparation for some of the samples. The selection of which samples require additional preparation is left to the discretion of the participant.
3. Collection and analysis of data from the samples supplied by the CPD. The number of samples will vary from 3 to 15 depending on the level of involvement requested.
4. Return of the results of the analysis along with relevant computer files to Ian Madsen.

Results required

Participants are asked to return the following (depending on the level of involvement - i.e., if you request powder samples as well) :-

1. The results of analysis of the CPD supplied data along with an estimate of the error in the determination.
2. For each sample supplied, a quantitative estimate of the amount of each phase present along with an estimate of the error in the determination. This information should be recorded on the 'standard' reporting forms on the floppy disc included with the samples and sent to Ian Madsen by (i) Email (qpa.rr@minerals.csiro.au), or (ii) mail to the address at the end of this document.
3. A brief description of the method of analysis used (i.e., single peak method, matrix flushing approach, Rietveld based method and so on ...)
4. A brief description of the instrument used to collect the diffraction data.
5. For participants using a Rietveld based approach, the final updated input file along with the final output file.
6. Details of any correction algorithms applied during the analysis for (i) preferred orientation and (ii) microabsorption.
7. The raw diffraction data is to be returned to the organisers for re-analysis with a 'standard' Rietveld code. This should be as an ASCII format file.

Description of samples

Sample 1 (simple)

This sample consists of a mixture of Corundum (Al₂O₃), Fluorite (CaF₂) and Zincite (ZnO) and is designated Sample 1G. The XRD pattern of this mixture has no serious overlap in the low angle region and will thus be suitable for a 'single peak' approach as well as profile fitting methods.

Late last year, many participants requested that the samples supplied for the round robin cover a wide range of compositions so that standardless least squares methods (which rely on the variation of phase content) could be applied. To assist in this, Sample #1 actually consists of 8 different mixtures sent to those participants who requested them. We realise that not all participants will have the need (or the time) to analyse all of these samples, and many participants have requested that only one mixture out of the 8 be sent. However, we would like as many participants as possible to analyse all 8 samples.

**** Please note that if you have been sent all 8 mixtures and have only limited time or resources, the one mixture in Sample # 1 that everybody must analyse is Sample # 1G. ****

Sample 2 (preferred orientation)

This sample consists of a mixture of Corundum (Al₂O₃), Fluorite (CaF₂), Zincite (ZnO) and Brucite Mg(OH)₂ and will test the problems encountered on the analysis of materials in which strong preferred orientation is present (the brucite crystals have significantly anisotropic dimensions along different crystallographic directions and exhibit strong preferred orientation along the 001 direction).

Sample 3 (amorphous content)

This sample consists of a mixture of Corundum (Al₂O₃), Fluorite (CaF₂), Zincite (ZnO) and Glass (SiO2). The glass does not provide a sharp diffraction pattern and exhibits only a broad diffraction peak at about 4Å.

Sample 4 (microabsorption)

This sample consists of a mixture of Corundum (Al₂O₃), Magnetite (Fe₃O₄) and Zircon (ZrSiO₄). The magnetite and zircon are natural materials and have been prepared with mean grain sizes of about 36 and 21m respectively. This, along with the large difference in absorption coefficient for commonly used X-ray wavelengths, should generate a significant microabsorption problem for X-ray users.

The sample is coarser than normally required for X-ray diffraction and may require some additional sample preparation.

Synthetic Bauxite

The synthetic bauxite sample has a mineral mixture similar to that found in some weathered lateritic profiles in the Darling Range, Western Australia with the exception that there is no aluminium present in the iron oxides used in the mixture.

The phases present are gibbsite, goethite, boehmite, hematite, quartz, kaolinite, and anatase.

Natural Granodiorite

This sample is a natural granodiorite from Lancefield Victoria and is similar to the material described in Hill, Tsamborakis and Madsen (1993). The sample contains major amounts of the phases quartz, feldspar, albite, biotite with lesser amounts of clinochlore, hornblende and traces of zircon.

Since many of the phases exhibit strong preferred orientation, this sample represents a real, but not insoluble, challenge to participants. A number of thin sections are being prepared in order to obtain estimates of phase abundance using optical microscopy as well as Electron Probe Microanalysis of individual phase composition. While this work will be conducted at CSIRO Minerals, thin sections could be made available on request to a limited number of very enthusiastic participants.

Note that some additional sample preparation may be required for the granodiorite sample.

Pharmaceutical samples

The pharmaceutical samples consist of 2 mixtures of the following materials:

Pharmaceutical 1	Pharmaceutical 2	Description
Mannitol	Mannitol	Common sugar
Sucrose	Sucrose	Common sugar
DL-Valine	DL-Valine	Amino acid
Nizatidine	Nizatidine	Active ingredient in the Axid®, a medicine for duodenal ulcers and gastric reflux
	Starch Flowable Powder	Amorphous polymer produced and stored by plants

Material Safety Data Sheets are included with the samples for reference

Further details of source materials

Synthetic bauxite

Data collection conditions

The selection of the instrumental (i.e. wavelength, geometry, slit settings) and data collection (start angle, step width and end angle) conditions is left to the discretion of the participant. In addition, the CPD is not prescribing the methods of data analysis to be used. This should enable the organisers of the round robin to determine some of the range of diffraction methods being applied quantitative phase analysis.

Data conversion

The CPD supplied data (on the enclosed floppy disc) are formatted as ASCII text files in a form suitable for the LHPM/RIET7/SR5 series of Rietveld analysis programs (which is a similar format to that required for the DBWS Rietveld program). Files in different formats will be available from the IUCr-CPD Round Robin Web-page at:

http://www.dl.ac.uk/SRS/XRD/IUCR/QARR/

If necessary, participants can convert the CPD supplied data to their preferred format using a number of free/shareware programs available on the World Wide Web. The most convenient converter for the LHPM/RIET7/SR5 format is the CONVERT for DOS software from CRI at the Web site:-
http://www.ceramics.irl.cri.nz/Convert.htm

Others include:

TPOSE for Windows from David Hay at:
ftp://ftp.minerals.csiro.au/pub/xtallography/david-hay-XRD-software

Convert for Windows from Nita Dragoe at:
http://www.hongo.ecc.u-tokyo.ac.jp:10080/~tdragoe/convert3.html

and Winfit from Stefan Krum at:
http://www.geol.uni-erlangen.de/html/software/soft.html

For those participants who have problems with conversion, contact Lachlan Cranswick by E-mail: l.cranswick@dl.ac.uk or log into the CPD web site at:
http://www.dl.ac.uk/SRS/XRD/IUCR/QARR/

Crystallographic Nexus CD-ROM's, which have all the data interconversion software listed above, are available by contacting Lachlan Cranswick at lachlan@melbpc.org.au

Acknowledgements

I would like to acknowledge the considerable efforts of the following individuals during this phase of the Round Robin:-

• Lachlan Cranswick of Melbourne, Australia for sample preparation/packing, useful discussion on experimental design plus endless assistance with the innumerable tasks involved in conducting a round robin.
• Edward Groleau of Eli Lilly & Co, USA for preparation of the pharmaceutical sample.
• Mark Aylmore of CSIRO Minerals, Western Australia - for preparation of the synthetic bauxite sample.
• Nicki Agron-Olshina of CSIRO Minerals, Victoria, Australia - for preparation of the granodiorite sample.
• Nikki Scarlett of CSIRO Minerals, Victoria, Australia - for packing of distribution materials.
• Rod Hill, Deane Smith and Jaraslov Fiala - for frequent useful discussion and on-going support of the project through the IUCr CPD.

Contact details

Ian Madsen
CSIRO Minerals
Box 312 Clayton South 3169
Victoria AUSTRALIA

Phone +61 3 9545 8785 direct

+61 3 9545 8500 switch

FAX +61 3 9562 8919

Email qpa.rr@minerals.csiro.au (for the round robin)

Ian.Madsen@minerals.csiro.au (for all other correspondence)