Re: [sdpd] LaB6

[Andrew Payzant <payzanta...@ornl.gov>]

Most likely a sample preparation/mounting problem - the LaB6 standards are
pretty stable over many many months, and unless you made big changes to your
instrument I would not expect this much variability.

You have not stated how you prepared your sample. This is the most obvious
source of error. The peak shift might be the result of a sample displacement
difference between your two experimental runs, and this same difference
could also explain the intensity variation. Also what did you do to ensure
the diffracting volume of LaB6 was identical?

Andrew
-- 
E. Andrew Payzant
Senior R&D Staff Member
Metals & Ceramics Division
Oak Ridge National Laboratory
1 Bethel Valley Road
PO Box 2008, MS 6064
Oak Ridge, TN, 37831-6064

ph: (865) 574-6538   FAX: (865) 574-3940
web: <http://html.ornl.gov/dtpgrp/staff/payzant.html>



> From: corinalupu <clupu...@rice.edu>
> Reply-To: sdpd...@yahoogroups.com
> Date: Fri, 23 Jan 2004 19:55:37 +0000
> To: sdpd...@yahoogroups.com
> Subject: [sdpd] LaB6
> 
> 
> Hello everyone,
> 
> I am glad that this group exists and I hope that I can get a good
> advice regarding the problem that I have.
> 
> First of all, I just want to mention that I am not expert in the X-
> ray powder diffraction technique and I just starting working more on
> it. 
> 
> I runned for the first time the LaB6 standard one month ago and I was
> able to get for the highest peak at 30.352 (2theta) an intensity of
> 62679 cps. Few days ago, the same standard I used to run again a
> profile. The position of the highest peak was at 30.65 (2 theta) and
> its intensity was 20098 cps. Today, I run it again and the drop in
> intensity went to only 3000 cps.
> 
> I need to mention that the storage of the LaB6 was in air in a vial
> covered with Al foil. If someone can mention if it's about a
> degradation of the standard (e.g. by oxidizing) or its an instrument
> problem I will really appreciate.
> 
> thanks,
> Corina 
> 
> 
> 
> 
> 
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> 


 

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