The Vacancy Defects In Yttriastabilized Zirconia : A Firstprinciples Calculation

Yttria-stabilized zirconia(YSZ),Y2O3 doped into Zr O2,can maintain its cubic structure over a wide range of temperature.YSZ is extensively used in many applications due to its high oxygen diffusivity at elevated temperatures and poor electronic conductivity.For example,it can be served as electrolyte in solid oxide fuel cells(SOFC) or used as conductor for oxygen sensors.Thus,a good understanding of its structure and phase stability is very important for us to have a better use of this material.So far,a great deal of work have been done on atomic conguration of YSZ,using both experimental and theoretical methods.However,there exist many literally discrepancies in different studies.A plane wave method based on density functional theory(DFT)was used to conduct our research.All the calculations are performed using the Vienna Ab initio Simulation Package(VASP).Then,combining the first principles calculation results with thermodynamic al modeling method,we can get the phase diagram of YSZ oxygen vacancy defects at different temprature and oxygen partial pressure.First,we optimized the lattice parameter of cubic zirconia and calculated the atomic configuration of cubic ziconia and YSZ(xxx-5.021?OYZr??,??0). The lattice parameter of cubic zirconia is??15.5 ?,which is very close to the experimental result.As for the oxygen vacancy distribution in YSZ,our results shows that oxygen vacancies have an alignment along 211??. The results we get in this way can offer data for the next step of calculating the the phase diagram of YSZ oxygen vacancy defects and also confirms that the parameteres used in this work are reasonable.Then,we calculated the atomic configuration and ground state energy of nonstoichiometric YSZ.Finally,combining first-principles calculation results with thermodynamical modeling method,we draw the phase diagram of nonstoichiometric YSZ oxygen vacancy defects at tempareture T=1000K and 1500 K.