Dear M. Bendoumia, usually, I would recomment to stop the ramp and remain at the desired temperature for the XRD measurement for several (mostly practical) reasons. First of all, the sample will change its position during heating. This is because the heater in your oven gets warm, and the sample will also expand during heating (with typically 10-6 / K. So the sample surface will lift when you heat the sample, and thus the position of the X-ray beam will change as a function of temperature. Therefore you should realign the sample in the beam BEFORE the X-ray diffraction, especially if you do not have a parallel beam impinging on your sample, which is the case in most laboratory diffractometers, If you don not realign the sample height, the geometry of the diffractometer will change as a function of sample temperature, and the angles measured for the diffraction peaks will change accordingly. Thus a change of measured Bragg angles may be misinterpreted ...

If you have a parallel beam optics (i.e. a Goebel mirror in a laboratory diffractometer or a synchrotron source), then those heigt effects may be not so important, if the sample is still in the beam anyway ...

A second reason for measuring at a certain temperature is that you do not measure the diffractogram in parallel, this means the low angle region of the diffractogram is measured at a lower temperature than the high angle part. If you want to perform a detailed analysis (Rietveld refinement etc), then the analysis will be erroneous, (because of different thermal disorder for different diffraction peaks etc).

Hope this helps, kind regards, Dirk

Dear M. BENDOUMIA, the process of high temperature XRD analysis could be changed according to your experimental. As the result of XRD  is different  when sample is heat with various holding times, you should be select the process by your self. If you want to know the information of sample at the desired temperature when it is heated at constant rate, you had better not to maintain the temperature. However, if you want to know its information at a temperature, i think you can try to do some tests with different holding times to check the influence. 

BEST REGARDS, Lingxue Kong.

For my experiment i want to calculate the crystallite size of my sample for different temperatures:

Firstly I have not enough of powder to make several experiments.

Secondly remains at the desired temperature I doubt that the size will change during recording of diffractogram.

But if you further increase the temperature, the crystallization will proceed even faster. So keeping it at a well-defined condition is certainly better than increasing the temperature further. And ageing at fixed temperature can be mathematically described - you don't know about the influence of an increased temperature.

What is your sample material you are interested in? What is the desired temperature range? Kind regards, Dirk

thank you for being interested in my question; after I have read your answers, I'm thinking :

either to achieve a quick scan (about 10 min) with remaining the temperature fixed and assume that during this time nothing will change (although I do not know how will it record and give a fixed peak width to a size which varies with temperature); or arriving at the desired temperature I returns to the ambient temperature, then I will run the XRD analysis (but this latter requires several tests so a large amount of powder)

My sample is an aluminum.

my respect

And what is the temperature range? If you have a 2D-detector, then you may record the entire diffraction pattern in some few seconds ...

We have a high-temperature cell which may cope with a vacuum environment, and a 2D-detector (enclosed a typical diffractogram of a quartz powder recorded in some few seconds), so it would be feasible to do such an experiment in-situ, i.e. heat the sample with a slow rate of some degrees per second (or minute), and record the diffraction patterns simultaneously (maybe with an error of some K), but you will get an enormous number of diffractograms that you may average ... Let me know if you are interested ...

Dirk

The temperature range is between [200-1000°C]

but the diffractogram which it is obtained at our laboratory and that I know how study is attached.

I'll do a little research on in-situ experiment and reorganize my ideas.

Many thanks for your help

If you want to get a diffraction pattern at high temperature. you have to follow the following step ;1) adjust your sample on the diffractometer on the require range of angles. 2) set your heating equipment on the diffractometer. evacuate the heating temperature equipmnt inorder to get rid of some oxgen remain. Pass at low rate  flow  liquid nitrogen flow into the heating equipment in  order to prevent your sample from oxidation during heating. more over you have to keap this nitrogen flow during the whole experiment. leave this flow for at least 5 minutes before starting to adjust your your temperature.Then adjust your temperature and start  heating the sample at the temperature required in the presence of the low flow of liquid nitrogen vapour in order to prevent sample from oxidation during all the experiment . keep heating the sample for five minutes in order to get the steady state after which the latices expansion stop to change. After this step swich on your X-ray and get your diffraction. hf you want to take another powder diffraction at another temperature just change the temperature and keap the new temperature for another five minutes  and take another powder diffraction. In all cases you have to keep the flow of nitrogen going on till the end of your experiment. 

@ Karimat: I would not use nitrogen in the presence of Al, since the Aluminum will rect forming AlN-phases ... In any case you want to investigate a reactive material such as Al, I would strongly recomment a vacuum environment!

The comments and proposal of Dirk are perfect. Anyway I will not recommend to perform the experiment neither under nitrogen (formation of AlN) nor under vacuum (owing to the relatively high vapour pressure of Al at temperatures ranging from 700 to 1000°C. I would prefer using pure as possible Ar or He gas...

Besides the best conditions to realize a perfect experiment is to use a synchrotron diffractometer equipped with a PSD detector. Not only the experiment will be realized very fast.. even upon a continuous heating (no step fixed temperature required), the sample could be small, always fully placed in the beam (no problem of realignement) and since the instrumental resolution should be very high, any change in the profile width resulting from the crystallite size will be perceptible..  The question is to access to a synchrotron facilities.Look to establish a cooperative research plan for that.

Daniel Fruchart

we have a diffractometer equipped with a Pixcel 1D detector, and i don’t know if it's faster than the SPD detector, and if it's more recommend for a no ambient XRD.

If you want to get accurate results specially if you are dealing with inorganic materials, then you have to follow the following steps. Calibrate your temperatures against the one previously made by company then adjust your sample on the diffractomer  on speciment holder, then adjust the wanted temperature, leave the specimen at the required temperature for at least five minutes before taking the diffraction patterns you   repeat the same steps if you choose another temperatures repeat the same steps  

Generally, while doing High temperature insitu XRD , definitely you have to maintain constant temperature at very precision level (+/- 1 deg C) while recording the diffraction. 

It is important to consider thermal expansion of atomic structure. With increasing the temperature, atomic fluctuations increase. It can change the d spaces, and consequently leads to peaks shift. The peaks shift might not related to sample movements. Therefore you might see some differences between high temperature pattern and reference cards.