Preparation And Properties Of Rare Earth Doped 8YSZ Powders And Ceramics

Zirconia is a kind of excellent structural and functional material and has wide application prospects in aerospace and defense industry due to its high toughness,high bending strength,high melting point of 2715?,high resistivity and refractive index,low coefficient of thermal expansion,excellent abrasion resistance and corrosion resistance,outstanding high temperature chemical stability and low phonon energy.In addition,zirconia is also an excellent rare earth luminescent matrix material,and it can broaden its application in optically functional transparent ceramics as doped with Ho³⁺and Yb³⁺.In this paper,8 mol%Y₂O₃ stabilized ZrO₂?8YSZ?and Ho³⁺/Yb³⁺doped 8YSZ powders were prepared by chemical co-precipitation method using ZrOCl₂·8H₂O,Y₂O₃,Yb₂O₃,Ho₂O₃ as raw materials.At the same time,the 8YSZ ceramics were prepared by hydrogen atmosphere sintering.The effects of sintering aids and sintering processes on the microstructure and mechanical properties of the 8YSZ ceramics were studied.The effects of calcination temperature and concentrations of Ho³⁺and Yb³⁺on luminescence properties of nanopowders were studied.The results indicated that the 8YSZ nanopowders prepared by co-precipitation exhibited a single cubic phase Zr O₂ with different ratio of alcohol to water.The 8YSZ nanopowders prepared at R=1.0 and calcined at 1000?presented near-spherical morphology with the particle size of 20 nm and had favorable dispersibility.Through changing the type and content of sintering aids,the relative density,hardness and fracture toughness of the samples added with sintering aids were higher than those of pure 8YSZ samples.They increased first,and then decreased with the increase of sintering aids contents.All of the relative density,hardness and fracture toughness reached the maximum values as the contents of ZnO,TiO₂ and La₂O₃ were 1wt.%.With different ratios of alcohol to water,8YSZ powders calcined at 1000?and doped 1 wt.%ZnO were cold isostatic pressing at 200 MPa and sintered at 1550?for10 h.When the R was 1.0,the grain of 8YSZ ceramics were uniform and dense with the size of 20-25?m,and the relative density,Vickers hardness and fracture toughness reached the maximum values of 98.89%,1369 HV and 3.06 MPa·m^1/2,respectively.Compared with 8YSZ powder prepared at R=0,the 8YSZ ceramics had better mechanical properties via the same sintering process.The upconversion luminescence intensity of Ho³⁺/Yb³⁺:8YSZ nanopowders increased with the increase of calcination temperatures,reaching the maximum value at the calcination temperature of 1200?.Its fluorescence intensity increased first,and then decreased with increasing the calcination temperatures,reaching the maximum value at calcination temperature of 1000?.The upconversion luminescence and fluorescence intensity of the Ho³⁺/Yb³⁺:8YSZ nanopowder both increased first,and then decreased with the increasing Ho³⁺and Yb³⁺doping concentrations,reaching the maximum values at the Ho³⁺and Yb³⁺concentrations of 0.2 mol%and 10 mol%,respectively.