Dear all,
with the occasion offered by this message I would like to spend few words about the spinning method to reduce texture effects.
In the Bragg-Brentano (or theta-2theta scanning case with sample surface normal to the scattering vector) spinning the sample around its normal does not reduce texture effects. This because the sample is in the center of an hypothetical pole figure and changing the so called phi or alpha angle does not change the texture. From a diffraction point of view the crystallographic planes diffracting are the ones parallel to the surface and turning them around their normal does not change nothing.
Actually due to the divergence of the beam there is a small effect, but it is very small, because it is like moving half a degree or maximum a couple of degrees from the center of the pole figure and unless you have an epitaxial thin film the change is unappreciable.
What in reality happens during spinning is that if the beam spot is not circular, but a line, you are sampling more volume in the sample (so it is equivalent to reducing grain size as Dipo Omotoso was pointing out) and this in some cases was erroneously attributed to decreasing texture effects.
So in the end when someone is selling you a spinning attachment for a Bragg-Brentano instrument because it help reducing texture effects, it is a lie (well, they may be don't know it is a lie).
Sorry, but it is a lot of time I desired to share this idea on the community and when I see still today these attachments sold around to reduce texture effects I cannot avoid to think about it (and laugh).
Luca Lutterotti
On Sep 9, 2004, at 16:30, Omotoso, Oladipo wrote:
Dear Andreas,
This may not be an option for your sample but grinding the sample to less
than 5 micron may help prevent fall out. In this size region, you may not
need to spin the sample to reduce texture effects.
Dipo Omotoso
