Stephen,
The NIST LaB6 can be used for Scherrer approximation and works fine. For
materials that have different peak locations I plot out all the FWHM of LaB6
and curve fit the function to get a better value of teh FHWM at the position of
the sample I am applying the correction on. However, for more precise work
(especially when using the Warren-Averbach approach) I use the same material in
the annealed state. I have found the NIST sample is one of the smallest B
(FWHM) values and various materials such as metals (which I work with often)
have a higher intrinsic defect count and hence a higher FWHM in the annealed
than say ceramics such as LaB6, often I am interested in what defects are added
due to some process.
Sorry about the error in my first response, I also I wanted to mention when I
discussed correction I was referring to the instrumental broadening correction
which you have obviously figured out.
Hope that helps,
Ed
----- Original Message -----
From: [EMAIL PROTECTED]
To: "Edward Laitila" <[EMAIL PROTECTED]>
Sent: Thursday, November 13, 2008 12:26:20 AM GMT -05:00 US/Canada Eastern
Subject: Re: Suggestion about software(s) for size profile-broadening
calculation
Dear Edward,
many thanks for your info. For the instrumental value (B), is it
necessary to use some standard? I got some NIST LaB6. Is it ok?
I wish this matter will not bother you lot of your spare time. Best wishes.
stephen
----- Message from [EMAIL PROTECTED] ---------
Date: Wed, 12 Nov 2008 14:54:23 -0500 (EST)
From: Edward Laitila <[EMAIL PROTECTED]>
Reply-To: Edward Laitila <[EMAIL PROTECTED]>
Subject: Re: Suggestion about software(s) for size
profile-broadening calculation
To: [EMAIL PROTECTED]
> Stephen,
>
> The peak profile gives information about the crystallite or coherent
> diffracting domain size along with microstrain. You cannot not get
> a grain size unless the crystallite size can be related to the
> grain size from knowledge of the microstructure. The crystallite
> size can be estimated using the Scherrer equation assuming no
> microstrains and a spherical shape. The equation is the thickness
> or size = (0.9 X lambda)/(breadth(radians) X sin(theata)), that is
> if I remember correctly since I am currently in the hospital. I
> hope this helps, a rather simple calculation that provides a good
> estimate. I should note there are correction schemes of gaussian
> and lorentzian (I normally use a geometric mean of the two) that is
> important when the breadth is only a couple of hundreds or less
> (please see B.D. Cullity Elements of X-Ray Diffraction in my
> opinion one of the best XRD references). Also the values change
> with angle so I typically have found averaging the values of the 5
> lowest angle peaks is close to the Warren-Averbach results.
>
>
> Cheers,
> Ed
>
>
> ----- Original Message -----
> From: [EMAIL PROTECTED]
> To: "Rietveld L" <Rietveld_L@ill.fr>
> Sent: Wednesday, November 12, 2008 5:42:37 AM GMT -05:00 US/Canada Eastern
> Subject: Suggestion about software(s) for size profile-broadening calculation
>
> Dear all experts in XRD,
>
> As stated in the header, does anyone know if there is some software(s)
> available for estimation of average crystal grain size using the peak
> breath of XRD data? I just want to know some rough values so as to
> compare my samples prepared at different conditions. Many thanks for
> your kind helps.
> Great appreciate.
>
> stephen
>
>
> --
> Engineer/Scientist
> Michigan Technological University
> Dept of Materials Science and Engineering
> Phone:(906) 369-2041
> Fax: (906) 487-2934
>
----- End message from [EMAIL PROTECTED] -----
--
Engineer/Scientist
Michigan Technological University
Dept of Materials Science and Engineering
Phone:(906) 369-2041
Fax: (906) 487-2934
