Phase transitions are well established for bulk silicon dioxide. But I would like to now increase of the surface area and go to nano structures. These phase transitions are stable or for instance temperature of phase transition reduced?
Regards
Phase transitions are being affected by particle size, since different phases (structures) have different surface energies (J/m2). As surface area increases (with decreasing particle size) the phase with the lower surface energy will become thermodynamically more stable with decreasing size. The same argument also explains the "shape" of particles. The particle will arrange the shape in such a way to reduce the overall surface energy as much as possible. Obviously there are also kinetic factors involved and they can sometimes counteract the thermodynamic driving forces.
You expect the \apha - \beta phase transition temperature to go down with decrease in particle size and the phase transition will probably suppressed as the paricle size is further reduced. It would be quite interesting to check what happens to the intermediate incommensurate phase on size reduction. My guess is that this phase will disappear before all other nanno-size effects. This hase should be most sensitive to the size reduction.
Phase transitions are being affected by particle size, since different phases (structures) have different surface energies (J/m2). As surface area increases (with decreasing particle size) the phase with the lower surface energy will become thermodynamically more stable with decreasing size. The same argument also explains the "shape" of particles. The particle will arrange the shape in such a way to reduce the overall surface energy as much as possible. Obviously there are also kinetic factors involved and they can sometimes counteract the thermodynamic driving forces.
Phase transitions in nano-crystals do show different behaviour from bulk but many factors such as the particle size, kinetic factors and phase compositions play a definitive role. It is true that phase with lower surface energy would prevail. You may like to go through our publications on phase transitions in nano-crystalline rare earth oxides which are available on researchgate.
Thank you dear Prof. Nita. Would you please specify in which papers you work on phase transition of nanomaterials?
You may go through the following:
Article Anomalous high pressure behaviour in nanosized rare earth sesquioxides
Article Pressure‐induced anomalous phase transformation in nano‐crys...
Article Raman scattering of rare earth sesquioxide Ho 2 O 3 : A pres...
Article Phase progression via phonon modes in lanthanide dioxides un...
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