Hafnia / Zirconia polymorphs as a function of T

  • Thread starter Useful nucleus
  • Start date
  • Tags
    Function
In summary, the polymorphs of hafnia and zirconia exhibit varying levels of symmetry as they are heated, with the monoclinic structure being less symmetric and the cubic structure being the most symmetric. This may seem counterintuitive, as heating typically leads to an increase in entropy, which is proportional to the number of accessible states. However, the symmetry of a structure can also affect the degeneracy, or number of accessible states, which can lead to a decrease in entropy. This may explain why the cubic phase has a lower entropy than the monoclinic one, despite being heated to a higher temperature.
  • #1
Useful nucleus
370
58
The room temperature polymorph of hafnia and zirconia is the less symetric monoclinic, by heating both of them trasform to the more ordered tetragonal structure, by further heating they transform to the cubic flourite structure and eventually they melt.

To me it looks counter intuitive that they get more and more symmetric by heating up to the melting point! Any explanations or thoughts?
 
Physics news on Phys.org
  • #2
Let me explain more,
My undesrtanding is that the entorpy is proprtional to the degenracy or the number of accesible states. Also heating adds more entropy to the system.
However, the symmetry tends to reduce the degenracy which (to me) seems to contradict that the entropy of the cubic phase should be larger than the entropy of the monoclinic one.

Am I wrong in my argument?
 

FAQ: Hafnia / Zirconia polymorphs as a function of T

What are Hafnia and Zirconia polymorphs?

Hafnia and Zirconia are two different crystal structures of the same compound, zirconium dioxide (ZrO2). They have the same chemical formula but different arrangements of atoms in their crystal lattices.

How does temperature affect the polymorphs of Hafnia and Zirconia?

At different temperatures, the atoms in the crystal lattice vibrate and move differently, resulting in different arrangements and structures. This can lead to a change in the polymorph of Hafnia and Zirconia.

What are the different polymorphs of Hafnia and Zirconia?

There are three main polymorphs of Hafnia and Zirconia: monoclinic, tetragonal, and cubic. The monoclinic form is stable at low temperatures, the tetragonal form at medium temperatures, and the cubic form at high temperatures.

Why is the study of Hafnia and Zirconia polymorphs important?

Hafnia and Zirconia are widely used in various industries, such as ceramics, refractories, and electronics. Understanding the polymorphs and their behavior at different temperatures is crucial for optimizing their properties and applications.

How is the polymorph of Hafnia and Zirconia determined?

The polymorph of Hafnia and Zirconia can be determined through various techniques such as X-ray diffraction, electron microscopy, and thermal analysis. These methods can provide information about the crystal structure and phase transitions at different temperatures.

Similar threads

Thermodynamics: Internal Energy, Heat and Work Problem
Replies
1
Views
1K
Problem set with air conditioners and thermodynamics
Replies
5
Views
2K
Glass transition temperature; slowly cooling it
Replies
2
Views
4K
Chemically regenerating my auto's catalytic converter?
Replies
19
Views
4K
Exploring Entropy: A Physics Student's Questions
Replies
21
Views
4K
Younger Dryas and the Gulf Stream Urban Myth
Replies
4
Views
4K
Creep failure and related question
Replies
4
Views
16K
Response to Deleted Thread that I've Worked on Too Hard to Let Go
Replies
1
Views
2K
Lab report questions, gas thermometer
Replies
3
Views
6K
Is my fictional Solar System stable and realistic?
Replies
21
Views
2K

Hot Threads

Recent Insights

Back
Top