YSZ: Mechanism of Stabilizing Zirconia (Cubic Phase)

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In summary, the conversation discusses the mechanism of stabilizing Zirconia (cubic phase) by Yttria, and proposes a model for understanding the stabilization of cubic and tetragonal forms of Zirconia. The conversation also mentions the interest in studying the behavior of RE-sesquioxides in transitional metal and actinide oxides. The question of why high temperatures are needed in the synthesis of stabilized Zirconia by solid state or hydrothermal processing is also raised.
  • #1
carmi
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Hi
I wanted to know what is the exact mechanism of stabilizing Zirconia (cubic phase) by Yttria
thanks
:confused:
 
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  • #2
Here is one proposal for the mechanism and is generally consistent with my understanding.

The microscopic mechanism leading to stabilization of cubic and tetragonal forms of zirconia (ZrO2) is analyzed by means of a self-consistent tight-binding model. Using this model, energies and structures of zirconia containing different vacancy concentrations are calculated, equivalent in concentration to the charge compensating vacancies associated with dissolved yttria (Y2O3) in the tetragonal and cubic phase fields (3.2 and 14.4% mol, respectively). The model is shown to predict the large relaxations around an oxygen vacancy, and the clustering of vacancies along the 111 directions, in good agreement with experiments and first principles calculations. The vacancies alone are shown to explain the stabilization of cubic zirconia, and the mechanism is analyzed.

Ref: Stefano Fabris, Anthony T. Paxton and Michael W. Finnis,
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TW8-47724Y1-S&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c9b5f2cc2365877671fc1380880c33a7
Acta Materialia, Volume 50, Issue 20, 3 December 2002, Pages 5171-5178

The behavior the RE-sesquioxides in transitional metal oxides and actinide oxides is of interest.
 
  • #3
Thanks a lot Astronuc
you really helped me

carmi
 
  • #4
Ysz

Hi,
please help to understand me why in the synthesis of stabilized Zirconia(YSZ, CSZ...etc ) by any solid state route or hydrothermal processing... high tempreature need for phase formation ?
 

1. What is YSZ and how does it stabilize zirconia in the cubic phase?

YSZ stands for yttria-stabilized zirconia, which is a ceramic material commonly used in high-temperature applications. The addition of yttria to zirconia helps to stabilize the cubic phase, which is the most stable and desired phase for many applications.

2. Why is stabilizing zirconia in the cubic phase important?

The cubic phase of zirconia has several desirable properties, including high strength and toughness, resistance to thermal shock, and good electrical and mechanical properties. Stabilizing zirconia in this phase allows it to be used in a wide range of applications, such as in solid oxide fuel cells, thermal barrier coatings, and ceramic knives.

3. How does yttria stabilize zirconia in the cubic phase?

Yttria has a similar atomic size and charge to zirconia, which allows it to replace some of the zirconia atoms in the crystal lattice. This disrupts the formation of the tetragonal and monoclinic phases, which are less stable, and promotes the formation of the cubic phase.

4. What are the factors that affect the stabilization of zirconia in the cubic phase?

The amount of yttria added, the temperature and time of sintering, and the cooling rate can all affect the stabilization of zirconia in the cubic phase. Higher yttria content and longer sintering times tend to result in a higher proportion of cubic phase, while rapid cooling can cause the formation of other phases.

5. Are there any limitations or challenges in stabilizing zirconia in the cubic phase?

One limitation is that the cubic phase is only stable at high temperatures, typically above 1200°C. This can make the manufacturing process more challenging and expensive. Additionally, zirconia can undergo phase transformations under certain conditions, such as mechanical stress or exposure to water, which can affect the stability of the cubic phase.

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