Study On Electrical Transport Properties And Structure Behavior Of Y₂O₃/ZrO₂ Under High Pressure

ZrO₂ solid solution has excellent properties such as high hardness,high melting point and good wear resistance.It has a wide range of applications in ceramic tools,oxygen sensor parts,artificial teeth and ceramic insulation.The excellent properties of ZrO₂ solid solution are inseparable from its structure and electrical transport properties.Therefore,it is of great significance to carry out related physical properties research for the application of ZrO₂.Pressure can bring new properties to a substance by compressing the atomic spacing and changing the crystal structure and band structure of the material.In this thesis,we studied the electrical transport properties and structural changes of Y₂O₃/ZrO₂ solid solution under high pressure by high-pressure in-situ impedance spectroscopy and synchrotron X-ray diffraction.The purpose is to understand the related properties of Y₂O₃/ZrO₂ solid solution under pressure.The study yielded the following results:1.Y₂O₃/ZrO₂ solid solution with cubic phase structure was prepared by chemical coprecipitation method.X-ray photoelectron spectroscopy analysis showed that the sample consisted of O,Y and Zr elements.The elements corresponded to the O²⁺,Y³⁺,and Zr⁴⁺states respectively which proved that the synthesized sample was Y₂O₃/ZrO₂.The ratio of each element in the sample is Zr:Y:O=19.88:24.62:55.5.The XRD pattern is consistent with the standard PDF card.The sample structure is cubic and space group isFm-3m.2.High-pressure in-situ AC impedance spectroscopy study was carried out on Y₂O₃/ZrO₂ solid solution.Only one semicircle can be seen in the impedance spectrum indicating that the grain and grain boundaries of the sample respond equally to the AC signal.As the pressure increases,the Y₂O₃/ZrO₂ solid solution resistance decreases.When the pressure is increased to 13.3 GPa,the resistance suddenly becomes large.Therefore,it is speculated that the structural phase transition may occur at 13.3 GPa,but it needs to be verified by X-ray diffraction experiments.3.By high-pressure in-situ synchrotron radiation X-ray diffraction,it is found that there is no disappearance or splitting of the diffraction peak in the diffraction pattern of Y₂O₃/ZrO₂ solid solution under high pressure.Through the refinement of Rietveld,it is found that the diffraction peak position is consistent with the cubic phase structure indicating that the crystal structure of the Y₂O₃/ZrO₂ solid solution is stable within the pressure range studied.When the pressure increases,the interplanar spacing d and the unit cell volume V decrease.The system undergoes structural phase transitions?secondary phase transition?at 13.1 GPa.Based on the second-order Birch-Murnaghan equation of state,we fit the data from the two stress stages.When the pressure is less than 13.1 GPa,the bulk modulus B₀=125 GPa.When the pressure is greater than 13.1 GPa,B₀=290 GPa and the bulk modulus increases by 132%.The material becomes more difficult to compress.The bulk modulus changes abruptly at13.1 GPa,which further indicates that the Y₂O₃/ZrO₂ sample undergoes an isostructural phase transition at 13.1 GPa.At the same time,it also shows that the abnormal change of the electrical transport properties of Y₂O₃/ZrO₂ solid solution is caused by the isostructural phase transition.