Effects Of CaO And Al₂O₃ On The Microstructure And Mechanical Properties Of Yttrium-stabilized ZrO₂ Ceramics

ZrO₂ ceramics can produce phase transformation and toughening effect during fracture,so they have excellent mechanical properties and are widely used in various fields.The mechanical properties of ZrO₂ ceramics largely depend on the grain size and phase transformability of t-ZrO₂ grains,and the grain size and phase transformability have a great relationship with the content and type of stabilizers incorporated.The radius and valence state of Ca²⁺are quite different from that of Zr⁴⁺.The solid solution of CaO in ZrO₂ will reduce the migration rate of grain boundaries.It has been reported that c-ZrO₂ phase has been found in zirconia stabilized by CaO.Al₂O₃ has high hardness and good dispersion properties.It is expected that CaO can reduce the grain size of t-ZrO₂ and increase the phase transformability.Al₂O₃ can help to stabilize the ZrO₂ matrix.Both can achieve the purpose of improve mechanical properties.In the first part of this subject,CaO with different contents was doped in Y₂O₃ stabilized ZrO₂.By using scanning electron microscope,X-ray energy spectrum analysis,high resolution transmission electron microscope,Raman spectrometer,X-ray diffractometer,Rietveld refinement,mechanical testing machine and other equipment and means to study the effect of CaO content on the microstructure and mechanical properties of Y₂O₃ stabilized ZrO₂ ceramics.The c-ZrO₂ grains of 1-3?m and t-ZrO₂ grains of 0.2-1?m are found in the microstructure of CaO and Y₂O₃ co-stabilized ZrO₂ ceramic.The content of CaO and Y₂O₃ in c-ZrO₂ grains are higher than that of t-ZrO₂ grains.As the content of CaO increases,the content of c-ZrO₂grains in the samples increases.A large amount of Y₂O₃ stabilizer enters the c-ZrO₂ grains,the content of Y₂O₃ in t-ZrO₂ grains decreases.The oxygen vacancies in t-ZrO₂ grains decrease,the phase transformability increases.At the same time,the grain size of t-ZrO₂ reduces.Therefore,the flexural strength and fracture toughness of the samples increase,and reach a maximum when the CaO content is 1.5 mol%,and then decrease.In the second part of the subject,on the basic of CaO and Y₂O₃ co-stabilizing ZrO₂,Al₂O₃with different contents was incorporated.By using scanning electron microscope,X-ray energy spectrum analysis,X-ray diffractometer,mechanical testing machine and other equipment and methods to study the effect of Al₂O₃ on the microstructure and mechanical properties of Y₂O₃and CaO co-stabilized ZrO₂ ceramics.In the microstructure of ceramics doped with Al₂O₃,t-ZrO₂ grains of 0.1-1?m,c-ZrO2 grains of 1-3?m,black plate-like grains of?7-12?×?1-3??m,internal t-ZrO₂ grains of 0.1-1?m inside black plate-like grains are found.When the Al₂O₃doping content is 1.5 mol%,the molar ratio of metal elements of black plate-like grains is Ca:Al:Cr:Fe:Co=1:9.4:1:1:0.3.With the increase of the amount of Al₂O₃,the content of black plate-like grains increases,a large amount of CaO entered the black plate-like grains,and the content of c-ZrO₂ grains decreases.The phase transformability of t-ZrO₂ grains increases first and then decreases,and the m-ZrO₂ phase content in the surface of samples decreases first and then increases.Therefore,the flexural strength and fracture toughness of the sample increase first,reaching a maximum when the amount of Al₂O₃ is 1.5 mol%,and then decrease.This subject has conducted in-depth research on the sintering process,phase transformation mechanism,and the effects of stabilizers CaO and Al₂O₃ on the microstructure and mechanical properties of yttrium-stabilized ZrO₂ ceramics.It is of great significance to optimize the content and type of stabilizers,and then optimize the mechanical properties of ZrO₂ ceramics.