With a 2D detector you see spots for "grains" and smooth peaks for
"texture". You can also observe a collection of grains which exhibit
texture giving a non uniform spot density. Usually by "grains" people
expect randomised changes in intensity with small orientation changes.
For "texture" there is a smooth variation of intensity with orientation
change.
Which is which depends on your beamsize and instrument resolution in
comparison to your grain size, and also what is the rocking width of an
individual grain.
Best,
Jon
On 25/10/2013 11:33, Angel L. Ortiz wrote:
Dear Collages:
I can understand the difference in the form of the rocking curve for
the cases of textured and un-textured materials. However, I would like
to know if there is any way to discriminate between the possible cases
of texture or graininess using the rocking curve or a set of rocking
curves. Is any difference expected in both cases (texture and graininess)?
Regards
--------------------------------------------------------------
Angel L. Ortiz, PhD
Associate Professor (Reader)
Materials Science and Engineering
Department of Mechanical, Energy and Materials Engineering
University of Extremadura, Badajoz 06006, Spain
(34) 924289600 Ext:86726 (Phone)
(34) 924289601 (Fax)
http://materiales.unex.es/miembros/personal/al-ortiz/index.html
---------------------------------------------------------------
*De:*rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] *En
nombre de *Mikko Heikkilä
*Enviado el:* viernes, 25 de octubre de 2013 10:56
*Para:* 'Angel L. Ortiz'; Rietveld_l@ill.fr
*Asunto:* RE: rocking curve
Dear Prof. Ortiz and other colleagues,
that is a good question, I suppose I need to think that a bit more, but
here’s my quick feelings about that. Since I measure with point detector
I measure just a “slice” from the full diffractogram I would see with a
2D detector, so I will get wrong intensities or even miss some
reflections if the sample is textured or very grainy. If I see a
reflection, set two theta to that angle and do a rocking curve (or equal
omega scan), I will have a probability with respect to surface normal of
finding crystallites with that lattice spacing. If I get a peak, then I
have an oriented film. If it’s just constant background, I’d say the
crystallites causing that reflection are evenly distributed and there’s
no orientation, like in this case of mine. If I have a veeery low amount
of crystallites, well, I’m not sure what would happen. Since that
rocking curve is in any case a sum of intensities of reflecting
crystallites, I suppose very small amount of crystallites would cause
the rocking to fluctuate in some manner (although I don’t think I’ll
ever have that small amount of crystallites). Then again even for small
amount but oriented crystallites it would give a peak, if all are
oriented to same direction.
That’s my thoughts, please correct me if I’m totally mistaken with this.
BR,
Mikko
*From:*Angel L. Ortiz [mailto:alor...@unex.es]
*Sent:* 25. lokakuuta 2013 11:19
*To:* 'Mikko Heikkilä'; Rietveld_l@ill.fr <mailto:Rietveld_l@ill.fr>
*Subject:* rocking curve
Dear colleagues
How can one distinguish between texture and graininess using the rocking
curve?. Which would be the expected difference in the rocking curve in
each case? I am not clear on this.
Regards
--------------------------------------------------------------
Angel L. Ortiz, PhD
Associate Professor (Reader)
Materials Science and Engineering
Department of Mechanical, Energy and Materials Engineering
University of Extremadura, Badajoz 06006, Spain
(34) 924289600 Ext:86726 (Phone)
(34) 924289601 (Fax)
http://materiales.unex.es/miembros/personal/al-ortiz/index.html
---------------------------------------------------------------
*De:*rietveld_l-requ...@ill.fr <mailto:rietveld_l-requ...@ill.fr>
[mailto:rietveld_l-requ...@ill.fr] *En nombre de *Mikko Heikkilä
*Enviado el:* viernes, 25 de octubre de 2013 9:32
*Para:* Rietveld_l@ill.fr <mailto:Rietveld_l@ill.fr>
*Asunto:* phase id for Friday refreshment
Dear Rietvelders,
I decided to completely embarrass myself and ask you a simple phase
identification question. I’ve had some trouble in trying to figure out
what’s going on with one measurement done in our lab. The sample is a
~30nm film heat treated in air at 500C, composition is Ce:Sn in close to
1:1 ratio plus oxygen in addition to those. I can’t tell if there’s any
very light elements as we only have EDX data at the moment, and the
actual amount of O is still unclear due to 3-4nm of native SiO2 under
the sample and I don’t have any XPS/RBS/SIMS profile data yet. I can’t
find anything from our databases that would fit even remotely close to
the measured data. (we have ages old PDF2 but I’ve imported every CeOx,
SnOx and CexSnyOz structure I could find from latest ICSD). Indexing is
a bit frustrating as well since I can’t be sure if it’s a single phase,
and I don’t have too much experience with unknowns anyway.
The measurement was done in grazing incidence mode with 1deg incident
angle (it seems that there was some 0.014deg of 2theta shift back then).
I’ve done rocking curve measurements from the first six reflections,
based on that it doesn’t seem to be textured so there shouldn’t be
reflections missing due to that (particle statistics is obviously a
different matter…). When measuring with different incident angles (from
0.25 to 3.75 2th) the diffractograms don’t seem to change, so there’s
probably no separate layers but one homogeneous matter. The data is
found here for those interesting in trying:
http://www.helsinki.fi/~mwheikki/temp/ And before you ask, there’s no
reflections below the one at 23.5 2th. And it’s a Cu tube.
I really appreciate any effort and time any of you might spend with the
data. I’m currently trying to find something from the literature but no
success so far. Hopefully you can make me feel stupid and find out the
easy solution before I do J
Have a nice weekend!
BR,
Mikko
---
Mikko Heikkilä, M.Sc., Laboratory engineer
Laboratory of Inorganic Chemistry
Department of Chemistry
P.O. Box 55 (A.I. Virtasen aukio 1)
FI-00014 University of Helsinki
phone: +358919150216
mobile: +358504160572
email: mikko.j.heikk...@helsinki.fi <mailto:mikko.j.heikk...@helsinki.fi>
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