The Influence Of Molding Parameters And Rare Earth Doping On The Properties Of Mg-PSZ

The MgO doped powders of ZrO2 were prepared by hydro-ball-milling technique from m-ZrO2, Mg?NO3?2, Al?NO3?3 and PVA. The powders were aggregated and spherical in shape with 150-200 nm in diameter. Then the research about the influence of pressure schedule on the densification of green bodies and sintered compacts has been conducted. The optimized process parameters were determined by the densification. The properties of Mg-PSZ including the thermal shock resistance were measured. The results show?1? the most densified process is the combination of dry press and isostatic press with a certain time of pressure maintaining and 1615? sintering temperature.?2? the content of PVA should be controlled in 5-7ml/100 g. This content can decrease the gas generation of green bodies which would result in a loose matrix, and also ensure the binding force between particles and the strength of green bodies.?3? The flexural strength of Mg-PSZ is 715 MPa, fracture toughness is 10.25 MPa.m1/2, and after 250?thermal shock test, the Mg-PSZ is in failure.Three different rare earth elements?Pr, Ce, La? were doped at the optimized process.The influence of rare earth doping on the properties of Mg-PSZ were studied. The results show:?1? the doping of Pr₂O₃ increased the porosity and content of monoclinic phase,decrease the grain size, the combined action results in the decrease of properties at room temperature. The increase of monoclinic phase reduce the coefficient of thermal expansion and enhanced the thermal shock resistance parameter?R? and thermal shock damage parameter?R'?, after thermal shock test, the residual flexural is significantly enhanced at the doping amount from 0.1%-0.3%mol.?2? as a kind of stabilizer, CeO2 can stable ZrO2 separately, but the generation of pores reduce the strength of matrix and its stabilizing effect was weaker than MgO. As a kind of dopant, CeO2 increase the porosity of Mg-PSZ and decrease the content of tetragonal phase which results in the ups and downs of properties at room temperature, but the phase change increase the high temperature properties.?3? the doping of La₂O₃ also decrease the room temperature properties slightly. The new generation phase La2Zr2O7 performs higher strength and lower thermal conductivity and coefficient of thermal expansion, but its lower fracture toughness results in a lower fracture toughness of the whole matrix.?4? the combination doping of Pr₂O₃/La₂O₃ can promote a obvious generation of La2Zr2O7 which is more than single doping of La₂O₃, after the cyclic thermal shock of 300? and 350?, the residual flexural strength tend to be stable, which guarantee the performance of Mg-PSZ at hightemperature.Specific doping mechanism of rare earth was proposed in this research by discussion of different doping results. The relationship between thermal shock resistance and rare earth doping was also explained. This study can provide technical guidance for the optimization of thermal shock zirconia materials.