Objective: To complete thermodynamic optimization of ZrO2-RE2O3 binary system with FACTSAGE software

The ZrO2-based materials are practically important as the thermal barrier coatings (TBC) for high temperature gas turbines, due to their low thermal conductivity, high temperature thermal stability and excellent interfacial compatibility. Studies of the phase equilibria, phase transformation, and thermodynamics of the ZrO2-RE2O3 systems can provide the necessary basic knowledge to develop the next generation TBC materials

II.  Background  v Phase diagram plays a vital role in the selection of

material and understanding the phase transformation behavior

v ZrO3-Y2O3 system present promising material for TBC application

Thermal Barrier Coating (TBC):

v Tetragonal → monoclinic is diffusionless martensitic transformation, which accounted for up to 8% destructive volume changes

v High temperature cubic structure can be stabilized to lower temperature by doping with RE elements

III.Thermodynamic  optimization

V.  Summary

Thermodynamic  Modeling  of  the  RE2O3-­ZrO2  SystemBilly  He,  Supervisor:  Prof.  In-­Ho  Jung

Department  of  Material  Engineering,  McGill  University

.

1. Pelton,  A.  D.,  et  al.  "The  modified  quasichemical model  I—binary  solutions."Metallurgical and  Materials  Transactions  B 31.4  (2000):  651-­659.

2. Wang,  Chong.  "Experimental  and  computational  phase  studies  of  the  ZrO2-­based  systems  for  thermal  barrier  coatings."  (2006).

3. Navrotsky,  Alexandra,  et  al.  "Thermodynamics  of  solid  phases  containing  rare  earth  oxides." The  Journal  of  Chemical  Thermodynamics 88  (2015):  126-­141.

I.  Abstract

IV.  Results

v Thermodynamic propertiesv Cp, ΔH298 and S298 of stoichiometric compounds.v Activity, Δ Hmixing of solutions.v Cation distribution ratio of solid solutions.v Gibbs energy measurements

v High melting point v Low thermal conductivityv Good wear resistance v No phase transformation

between room temperature and operating temperature

VII. Reference

v A complete critical evaluation and thermodynamic modeling of available phase diagrams and thermodynamics data was conducted on Y2O3-ZrO2 and La2O3-ZrO2 system.

v All experimentally reported enthalpy of formation data on RE2Zr2O7 compounds are collected on the same graph for systematic review.

v The solubility of pyrochlore phase in La2O3-ZrO2 was simplified as stoichiometric compound for now.

v In the future, the optimization of remaining RE2O3-ZrO2 systems will be completed based on the parameters in the two completed systems.

VI. Acknowledgement This work was supported by NESERC and a Gruber SURE award to Billy.I would also like to thank Prof. Jung and Junghwanfor their help.

Y2O3

Y2O3

Y2O3

Y2O3

Activity  of  Y2O3  in  tetragonal  phase  at  1300K

ZrO2                                                                                                                                                                                                                                                                                                            Y2O3

activity

0 0.20 0.40 0.60 0.80 1.00

0

0.20

0.40

0.60

0.80

1.00

ZrO2

ZrO2

ZrO2

ZrO2Y

2O3

Y2O3

Y2O3

Y2O3

Activity  of  ZrO2  in  cubic  phase  at  2773K

ZrO2                                                                                                                                                                                                                                                                                                            Y2O3

activity

0 0.20 0.40 0.60 0.80 1.00

0

0.20

0.40

0.60

0.80

1.00

Enthalpy  of  mixing  of  cubic  phase  at  973K

ZrO2                                                                                                                                                                                                                                                                                                            Y2O3

Delta  H(J)

0 0.20 0.40 0.60 0.80 1.00

-­10000

0

10000

20000

30000

40000

50000

60000

Optimized  ZrO2-­Y2O3  phase  diagram  

Optimized  ZrO2-­La2O3  phase  diagram