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: Michael Nippus <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
Date: Mon, 10 May 2004 12:19:08 +0200
To: [EMAIL PROTECTED]
Subject: RE: Reference Materials for temperature Calibration.
There was a ICDD 2003 Meeting Report, see Powder Diffr., Vol. 18, No. 2, p189, where Scott T. Misture presented some "preliminary results on generating full temperature calibration curves" on XRD. Scott is Chair of The Task Group on High Temperature Calibration, he wrote. May be he has more publishable works, in the meantime.
mailto:[EMAIL PROTECTED]
Cheers
============================================
Dr. Michael Nippus
Huber Diffraktionstechnik GmbH & Co. KG
Sommerstrasse 4
D-83253 Rimsting / Chiemsee, Germany
mailto:[EMAIL PROTECTED]
http://www.xhuber.com <http://www.xhuber.com/>
Tel: +49(0)8051 68780
Fax: +49(0)8051 687810
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-----Original Message-----
From: Andrew Payzant [mailto:[EMAIL PROTECTED]
Sent: Friday, May 07, 2004 2:08 AM
To: Rietveld list
Cc: Namsoo Shin
Subject: Reference Materials for temperature Calibration.
This depends on exactly what you want to calibrate, and how. Do you want an external standard to characterize the instrument, or an internal standard to improve your accuracy for refining a particular sample diffraction pattern, or something else again?
There are many choices for standards. You can use known melting point or phase transformations to establish particular temperature calibration points, or use lattice parameters and thermal expansion data to cover a large range. A standard with a large thermal expansion coefficient reduces your uncertainty in temperature calibration. Of course, in some situations you might prefer a low or near zero thermal expansion coefficient material to calibrate the 2theta rather than the temperature.
MgO is a good choice for temperature calibration for many situations – large thermal expansion coefficient and relatively unreactive with many samples. Noble metal powders (Pt, Au, Ag) are also useful, but you need to be extremely wary of melting points and reactivity with heater, sample, and atmosphere. Even LaB6 can be very useful for these calibrations (up to about 800degC). I recall that Andy Drews from Ford Research Labs had a paper in Advances in X-ray Analysis a couple of years ago using a 2-standard method for calibration. You might look into that.
If you are using a strip heater you can use the difffraction from the strip itself to confirm the calibration of your thermocouple, but your sample temperature will very likely be different from the strip temperature in this case, even for a thin powder layer. For thick powders or polycrystalline solids the temperature difference is usually more severe.
If you send me more details on what you are planning (Instrument, furnace type, sample chemistry, etc) I might be able to give a more detailed answer.
Best regards,
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: Namsoo Shin <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
Date: Fri, 07 May 2004 00:20:46 +0900
To: [EMAIL PROTECTED]
Subject: Reference Materials for temperature Calibration.
Dear all
Can anyone tell me reference powders for XRD temperature calibration in th range from R.T to 1000 degreeC?
Thanking in advance
Namsoo Shin
