On electron probe micro-analiser (EPMA) WDS I had tried to measure some concentrations on 2nd order lines to overcome numerous other problems (i.e. 40 minor/major elements, peak overlap "hell", spectrometer saturation at very high count rates...). After calibration those worked incredible well for two months, but at the moment those calibrations are terribly outdated, while 1st order lines keeps very similar intensities. It is not question of position, looks like intensities of those 2nd order lines had degraded with change of season. Thus my concern is if higher order diffraction intensities depend from some physical parameters (like temperature, as spectrometers are under vacuum). The observed intensity drop is on TAP diffracting crystal, where I was measuring Si Ka, Mg Ka and Al Ka on second order lines evading HFSE, REE overlap hell. Could temperature influence probabilities which order of diffraction (or the path) photon will take? Am I missing some other physical properties/process which could influence that?
Dear Petras Jokubauskas ,
you are right;
The XRD peak heights decrease by the temperature via the Debye-Waller factor.
There is a monotonous decrease for increasing temperature and for increasing theta (and thus the diffraction order).
You may have a look at the description of the Debye-waller factors in x-ray diffration books, such as of Cullity*) or the book of Klug and Alexander (X-Ray Diffraction Procedures, p. 145 ff)).
There is an exponential function exp(-2M) with M=B(T)*sin2(theta)/lambda2.
But for the TAP crystal I do not have data about B.
*) see page 135ff of:
https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjJ0sKzgIv6AhUD4aQKHb1XAasQFnoECAsQAQ&url=https%3A%2F%2Fwww.researchgate.net%2Fprofile%2FAhmed-Saeed-Hassanien-2%2Fpost%2FWhat-is-X-ray-Powder-Diffraction-XRD%2Fattachment%2F59d64e6a79197b80779a7c1f%2FAS%253A492613493313536%25401494459617709%2Fdownload%2FB.%2BD.%2BCULLITY-Elements%2Bof%2BX-RAY%2BDIFFRACTION-SECOND%2BEDITION.pdf&usg=AOvVaw0bV5U2EZWLC_OSpLJyUms_
Best regards
G.M.
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