For example, if someone prepares a powder sample, by ball milling/any technique using two different raw materials, and performs heat treatment to that powder at a specific temperature. Simultaneously he characterizes that powder by X-ray diffraction (XRD) to analyze its phase details.
So, in this case, is it possible to co-exist two different kinds of crystalline structures or two different phases (namely, monoclinic/triclinic or cubic/any other) at the same time for that powder sample??
Thank you for your precious answer in advance.
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Lead Zirconate Titanate Pb(Zr,Ti)O3 ceramics is one among such systems which shows two phase coexistence i.e both rhombohedral and tetragonal crystal structures at room temperature after ball milling of raw materials and calcination at approximately 1000 C. XRD analysis results indicate both phases.
You can find many articles for such systems.
Hope this helps you
Hello Abdul,
as mentioned by Premkumar S. this situation is absolutely possible and not uncommon. For another typical example lease have a look at the following interesting article:
Two-phase coexistence in Fe–Ni alloys synthesized by ball milling
The full text of this paper is freely accessible from the internet (please see attached pdf file).
By the way, you can find and access other potentially useful research articles about this topic by searching the "Publications" section of RG for the term "two-phase coexistence":
https://www.researchgate.net/search.Search.html?type=researcher&query=Two-phase%20coexistence
Good luck with your work!
Dear Abdul Moyez ,
in addition to the comments of Dr Frank T. Edelmann and Dr Premkumar S. , even in non-binary material, the co-existence of two different crystalline structures is very common. The geoformation for natural materials or the synthetic route for a binary system, for instance, will generate the conditions for the occurrence.
Naturally, it is a matter of stability. A second phase of the same material may appear as a synergic effect overall process. The impurities' presence may act as a catalyzer. Nevertheless, a gradient of temperature or pressure during the formation may trigger the second crystal structure formation.
As a natural example, for instance, gamma-Fe2O3 and alfa-Fe2O3 coexist in several young soils samples.
As you deal with alloys, it is not uncommon to find mixtures of phases, even on the boundaries, as the necessary conditions for one formation may slightly change given rise to the second or even third one. The phenomenon is observable when HTSEM is applied, and different fringe patterns rose.
Best regards,
WNM
TiO2 is another example. Depending on the size the particles (crystallites) rutile is more stable for larger sizes, while anatase is more stable for smaller sizes. So, depending on the milling and the temperature , you’ll find either more rutile or more anatase, in most cases, however, a mixture of both phases.
The case of coexistence of three structural modifications, ie polymorphs, is known from the geological environment too (rmetamorphic rocks, metapelites). This is the Al2SiO5 system (andalusite-sillimanite-kyanite).
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