Hi Apu,
It is definitely case dependent. If you have a sample with a known (small)
quantity of the second phase, you can do a quantitative analysis and obtain the
phase fraction. Then, just diminish the phase fraction until you see the point
of disappearance. It disappears when the largest set of peaks is not
distinguishable mathematically from the noise. Obviously this depends on the
quality of the diffraction from the phase and the level of noise in that
particular diffractometer for that sample.
On the warhorse instrument I use the most (Siemens D5000 with CuKalpha
radiation and position-sensitive detector) the limit is usually 1% but is worse
for iron-bearing (or otherwise fluorescent) samples and better for very nicely
crystalline and strong scatterers with high symmetry/multiplicity such as
rutile, just for an example.
- Kurt
________________________________________
From: rietveld_l-requ...@ill.fr [rietveld_l-requ...@ill.fr] on behalf of
Suchomel, Matthew R. [sucho...@aps.anl.gov]
Sent: Thursday, May 01, 2014 1:57 PM
To: Apu Sarkar
Cc: rietveld_l@ill.fr
Subject: Re: Phase volume fraction
With the appropriate sample and high-resolution synchrotron powder diffraction
data, you can do even better than 0.1 wt%.
Here at the APS beamline 11-BM, we've managed to perform quantitative
refinements on a suspected very dilute ZrB2 impurity in the NIST SRM LaB6 660a
powder sample, at a level of 0.068 wt% ZrB2. The accuracy of this value is
supported by complimentary XRF data showing a calibrated Zr concentration of
617 ppm in the LaB6 sample.
These data (from J. Faber) are currently in press as proceedings from the 2013
DXC meeting.
It would be difficult to reproduce this level of sensitivity with more 'real
world' samples and conditions - but it shows in principle what can be achieved.
Especially if you submit samples for the free rapid access measurement program
here at the APS beamline 11-BM.
http://11bm.xray.aps.anl.gov/users_new.html
[please forgive the flagrant advert!]
Matthew Suchomel
Advanced Photon Source
Argonne National Laboratory
> I guess you are talking about detection limit only, not quantification limit,
> right?
> The answer largely depends on your material (scattering power, domain size),
> tube (sampling volume) and counting time. I have seen cases where you can
> clearly see something below 0.1 wt% and cases where already the percent was
> off limits.
> Matteo
>
> -----------------------------------------------------------------
>
> Matteo Leoni, PhD
>
> DICAM
> University of Trento
> via Mesiano, 77
> 38123 Trento
> Italy
>
> Tel +39 0461 282416 Fax +39 0461 282672
>
> e-mail: matteo.le...@unitn.it
> ----------------------------------------------------------------
>
>
> -----Messaggio originale-----
> Da: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] Per conto di
> Apu Sarkar
> Inviato: giovedì 1 maggio 2014 22.24
> A: rietveld_l@ill.fr
> Oggetto: Phase volume fraction
>
> Hi,
> Can any one tell me what is the minimum phase volume fraction that can be
> detected by a laboratory X-ray diffractometer. In there any reference for
> this.
>
> I am using the new Empyrean from PANalytical.
>
> Thanks
> Apu
>
> Department of Nuclear Engineering
> NC State University
> Raleigh, USA
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