Hi all,
This is to say that I'm am nearly finished with the re-certification of SRM 676 for amorphous content. The revised certificate, offering a discussion as to the certification method, will be on the NIST website shortly, after the review process is completed. The certified phase purity of SRM 676 (retroactive to units in the field) is 91.75% +/- 1.5%.
Regards,
Jim
At 01:44 PM 5/6/2004 -0400, you wrote:
Robert
As previously mentioned many Rietveld programs will do what you want if you're willing to do the amorphous content calculations by hand afterwards. Some commercial software has it built in. I've done work in this area, and there are some pitfalls of which you must be aware, or your results may be VERY unreliable.
1. microabsorption. If your phases are similar in composition and your 'spike' phase has a similar absorption then this might not be a problem. However, there are instances in which extreme microabsorption can make a accurate determination practically impossible (other than possibly changing your tube to a more friendly wavelength). There is the Brindley correction that can sort of correct moderate microabsorption, but you need to know your particle size, and ideally it needs to have a narrow distribution. Reducing the particle size of your sample to sub-micron levels helps significantly.
2. spike phase. Many so-called crystalline phases aren't as fully crystalline as you might think. The SRM676 alumina had it's amorphous content measured a while back using neutrons and came out as 1.77 +- 0.68%. It doesn't sound alot but can make a big difference to your final results. Many 'crystalline' phases can be significantly higher. Microabsorption can be an issue with the spike so choose your spike carefully, and ideally standardise it using SRM676. Remember to include the error in the SRM676 amorphous content if quoting absolute amorphous contents rather than relative amounts.
3. particle statistics. This is equally as important when looking at purely crystalline materials, but errors due to poor particle statistics can really mess up amorphous content work. Ideally, micronise your sample before running it, but if they're nanomaterials then it might not be an issue.
4. surface roughness. I noticed that you probably work with nanomaterials. They tend to be fluffy, and such samples (at least on our instrument) show noticeable surface roughness effects on low angle reflections. If this is the case for your samples then you will either have to correct it or densify your sample somehow (or both).
Some of this stuff was covered in the results of the quantitative analysis round robin a while back:
Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 1a to 1h I. C. Madsen, N. V. Y. Scarlett, L. M. D. Cranswick and T. Lwin, J. Appl. Cryst. (2001). 34, 409-426
Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 2, 3, 4, synthetic bauxite, natural granodiorite and pharmaceuticals N. V. Y. Scarlett, I. C. Madsen, L. M. D. Cranswick, T. Lwin, E. Groleau, G. Stephenson, M. Aylmore and N. Agron-Olshina J. Appl. Cryst. (2002). 35, 383-400
It would be useful to cross-check your technique on a couple of dummy samples if at all possible to make sure you're not being mislead. Have fun!!
Pam
Dr Pamela Whitfield CChem MRSC Energy Materials Group Institute for Chemical Process and Environmental Technology Building M12 National Research Council Canada 1200 Montreal Road Ottawa ON K1A 0R6 CANADA Tel: (613) 998 8462 Fax: (613) 991 2384 Email: <mailto:[EMAIL PROTECTED]> ICPET WWW: http://icpet-itpce.nrc-cnrc.gc.ca
-----Original Message----- From: Robert Mauricot [mailto:[EMAIL PROTECTED] Sent: May 6, 2004 10:57 AM To: [EMAIL PROTECTED]
Dear all,
I have a powder diffraction of an amorphous multiphase material. I want to do a quantitative analysis of the amorphous phase. Can anyone tell me what software does it.
Sincery
R.mauricot
Cemes-CNRS Toulouse 31077 France Laboratoire NaNomat
James P. Cline [EMAIL PROTECTED]
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