I have prepared zirconia electrolytic thin films on NiTi alloy by cathodic electrodeposition process in zirconyl nitrate solutions and the films were then heat treated at 450 degree Centigrade . Due to the films' very low thickness, I analyzed their crystal structure by Grazing-XRD method. I did not surprise not to detect Zirconia, due to low thickness of the films, but I did not expected very intense peaks related to ZrO! How can it be possible?
Short answer is that there is a big difference, often ignored, between thermodynamics and kinetics.
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Phase diagrams always only show the equilibrium phases for various proportions of the elements at various temperatures. All the information is about thermodynamics. There is no information about kinetics on phase diagrams or in the thermodynamic knowledge that ZrO2 is the equilibrium phase. Kinetics, on the other hand, gives information about reaction rates. We all know that ZrO2 is the equilibrium phase, but to determine whether any particular conditions will have sufficiently rapid kinetics to produce any measurable amount of ZrO2 is a completely different question.
In view of that, I suggest checking that your temperature is high enough, as a starting point. In addition to temperature, composition, purity, nature of impurities, surface characteristics, crystallite sizes, crystallite perfection, and other things will effect transformation rates.
Thank you Mr. Boyer
You mentioned an important issue about the kinetics of process. I applied 450 degree centigrade for 1 hour and I suppose, 1 hour is not a sufficient length of time for heat treatment of the films to fabricate ZrO2, which is the equilibrium phase.
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