Dear Maria,
We are also working on methods for determination of amorphous material.
Can you please send me the full reference to the paper you quoted in
your message.
I urge great caution in the application of the Brindley model for
correction of your QPA. Since the microabsorption correction is based on
(MU - MUaverage)*R where MU is the linear absorption coefficient (LAC)
of the phase and MU average is the LAC of the mixture and R is the
particle radius. In your case MU and MUaverage should be the same (due
to having the same/similar chemistry) and only differ because of packing
density. Any difference in particle size may induce some microabsorption
issues, but estimation of the correct value of R is problematic at best.
The recent round robin on quantitative phase analysis highlighted the
fact that while microabsorption is the greatest impediment to accuracy
in QPA, misuse of the Brindley model frequently served to degrade,
rather than improve, accuracy.
Cheers
o----------------------oo0oo---------------------------o
Ian Madsen
Team Leader - Diffraction Science
CSIRO Minerals
Box 312
Clayton South 3169
Victoria
AUSTRALIA
Phone +61 3 9545 8785 direct
+61 3 9545 8500 switch
+61 (0) 417 554 935 mobile
FAX +61 3 9562 8919
Email [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
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-----Original Message-----
From: Fabra-Puchol, Maria
[mailto:[EMAIL PROTECTED]
Sent: Tuesday, 2 October 2007 7:46 PM
To: [email protected]
Subject: Density calculations for amorphous products
Hi all,
I have a question concerning density calculations,
I'm actually working on an amorphous phase quantification method
using Rietveld and most part of the samples I'm working with contain
high quantity of silica (amorphous and crystalline).
I've attentively read the paper: "Determination of the
crystallized fractions of a largely amorphous multiphase material by the
Rietveld method" (X. Orlhac, C. Fillet,...) and I found out that the
Brindley correction can be applied in my case.
When I calculate the linear absorption coefficient of each phase
I must to take into account also the amorphous phase, isn't it? . I just
would like to know if someone could indicate me how to calculate this
factor making difference between an amorphous and a crystalline phase
(for example, concerning silica).
I know the atomic absorption coefficient of each element must be
multiplied by the packaging density in the case of powders but it just
talks about the crystalline phases, what about the amorphous phase?
Thanks for your help
Sincerely,
Maria Fabra Puchol
Responsable Laboratoire Structures
Structural Laboratory Manager
-------------------------------------
Saint-Gobain CREE
550 Avenue Alphonse Jauffret
BP224
84306 Cavaillon Cedex - France
tel: 00 33 4 32 5 09 36
fax: 00 33 4 32 50 08 51
e-mail: [EMAIL PROTECTED]
