the answer largely depends on what you mean by "crystallinity". Do you mean how much of your material is crystalline or do you mean how large the crystalline domains are in a fully crystalline system? Both terms are used in different fields.

Facts:

* you always get a diffraction pattern, independently of the range of order of the material you analyze. If you have a perfectly crystalline fraction and you have something else, the pattern are simply added one another.

* one of the differences between an amorphous an a crystalline system is a heat of crystallization. If the system is properly amorphous it also shows a Tg.

So, with diffraction you can easily guess if your specimen has a crystalline component and, in several cases, you can understand if there is something else (poorly crystalline, very nano or amorphous). With total scattering you can also try to understand a bit more about the structure of this extra stuff.

With DSC you can easily see the Tg (typical of a glass) and, if the system crystallizes, a crystallization peak. So you can get info on the non-crystalline fraction

So I would first go for a thermal analysis (perhaps coupled with a TGA) to be sure about the nature of the system. I then pair this with XRD to understand how the evolution occurs, at least over a certain range.

Gyorgy, synchrotron radiation is not a "rare and expensive technology". If you have a strong scientific case and you can demonstrate that the experiment cannot be done in the lab, you are likely to get some beamtime. Nowadays, unless the kinetics are particularly fast, using one of the new generation detectors, a hot or a cryo stages you can easily follow crystallization in a lab.

X-ray diffraction method is suitable for checking the crystallinity of materials. DSC does not probe the crystallinity at all at least not directly. You can however use neutron and electron diffraction as well but these not always available. X-ray diffraction is almost always available in a material science and condensed matter laboratory. It is also fairly easy to interpret the results.

XRD is a regular and preferred method to tell about crystalline quality of a material than DSC.

The advantage of X-ray diffraction is that it provides information about the crystal structure. Powder X-ray helps you to identify the material(s) involved, including the crystalline type (alpha, beta, gamma etc.), and the average crystallite size. Pole diagrams on oriented materials helps you to get more deatils on crystallite orientation and structure. Single crystal X--ray allows the exact identification of the crystal structure down to the atomic level (elementary cell structure). (Hydrogen atoms not included, these can be studied by netroun diffraction of single crystals). DSC provides "only" thermal data, but it is indispensable if you want to study crystallization rate, recrystallization, secondary crystallization. From the breadth of the melting peak you may even get estimation of crystlline size distribution (at least in the case of polymers, I do not know how much it applies to metals or other inorganic crystals). Such kinetic data cannot be obtained form X-ray diffraction, unless you use synchrotron radiation (but that is a rare and expensive technology). Therefore in my opinion these two techniques are rather complementary than competing technologies.

the answer largely depends on what you mean by "crystallinity". Do you mean how much of your material is crystalline or do you mean how large the crystalline domains are in a fully crystalline system? Both terms are used in different fields.

Facts:

* you always get a diffraction pattern, independently of the range of order of the material you analyze. If you have a perfectly crystalline fraction and you have something else, the pattern are simply added one another.

* one of the differences between an amorphous an a crystalline system is a heat of crystallization. If the system is properly amorphous it also shows a Tg.

So, with diffraction you can easily guess if your specimen has a crystalline component and, in several cases, you can understand if there is something else (poorly crystalline, very nano or amorphous). With total scattering you can also try to understand a bit more about the structure of this extra stuff.

With DSC you can easily see the Tg (typical of a glass) and, if the system crystallizes, a crystallization peak. So you can get info on the non-crystalline fraction

So I would first go for a thermal analysis (perhaps coupled with a TGA) to be sure about the nature of the system. I then pair this with XRD to understand how the evolution occurs, at least over a certain range.

Gyorgy, synchrotron radiation is not a "rare and expensive technology". If you have a strong scientific case and you can demonstrate that the experiment cannot be done in the lab, you are likely to get some beamtime. Nowadays, unless the kinetics are particularly fast, using one of the new generation detectors, a hot or a cryo stages you can easily follow crystallization in a lab.

Dear Matteo, thank you for correcting my outdated information.

DSC usually researcher use to understand the phase change of the material when temperature increases or decreases. On the other hand XRD is a very useful tool to characterize crystal structure, phase, plane, grain size, crystallinity etc. Therefore it is preferable to use XRD instead of DSC for characterization of the crystallinity of the material. Thank you.

I agree with Abhijit and Gyorgy. I don't know how informations do you need,

but if I were you I would have done in the first place XRD. This is the best and easiest method to determine the crystal structure of materials. On the other hand DSC is the best method to understand the phase change during change the temperature.

I wish you luck in your research.

In my opinion, the more techniques you use, the better infomation you get on your system. XRD and DSC are both very convinient in the crystallinity studies. If the techniques are used properly, the information never can be contradictory, but complementary.  I did not find any suggestion in the comments the use of Modulated DSC. This technique is very useful mainly when you find glass transitions followed by a  crystallization.