Study On Preparation And Performance Of Nano-Zirconia Ceramic Powders

In this work, the liquid coprecipitation method was adopted to prepare Y₂O₃-ZrO₂, MgO-ZrO₂, Al₂O₃-ZrO₂ and CaO-ZrO₂ composite ceramic powder by using ZrOCl₂·8H₂O as raw material, Y(NO₃)₃·6H₂O, MgCl₂·6H₂O, AlCl₃·6H₂O, and Ca(NO₃)₂·4H₂O as dopant respectively, and NH₃·H₂O as the precipitant. The green compacts were formed by dry pressing and were sintered by pressureless sinteration. The effect of the reaction media and calcining temperature on the size and dispersity of the powders as well as the property of the powders, the dosage of the dopant and the compacting pressure on the density of the green compacts and sintered bodies were studied. The calcining temperature of the precursors was determined by thermogravimetry differential thermal analysis (TG-DTA), the morphology, size and distribution of the particles were studied by transmission electron microscopy (TEM), the phase composition of the powders was detected by X-ray diffraction (XRD), the microstructure of sintered bodies was analyzed by scanning electron microscopy (SEM), and the mechanical property of sintered bodies was characterized by Vickers hardness (HV).The experiment results showed that when ethanol was used as the reaction medium the sizes of the nano-zirconia composite powders were less than 30 nm and the powders had the narrow size distribution, good dispersity and high sintering activity. The form of ZrO₂ was mainly tetragonal with minor monoclinic. With the calcining temperature rising, the grain size of the powder was enlarged, and the content of monoclinic-zirconia had the trend of increasing. The fractured surfaces of the sintered bodies prepared by the composite ceramic powders were smooth without any cracks. The optimal pressure for Y₂O₃-ZrO₂, MgO-ZrO-2, Al₂O-3-ZrO₂ and CaO-ZrO₂ sintered bodies were 10MPa, 7MPa, 20MPa and 20MPa, respectively. The relative densities of the ZrO₂ green compacts respectively doped with 3%(mol)Y₂O₃, 5%(mol)MgO, 20～60%(mol)Al and 5～20%(mol)CaO were about 50%. The relative densities of the ZrO₂ sintered bodies respectively doped with 3%(mol)Y₂O₃, 10%(mol)MgO, 20～80%(mol)Al and 5～15%(mol)CaO exceeded 95% and were close to the theoretical value. The 80% (mol) Al doped-ZrO₂ sintered body had the biggest Vickers hardness.Y₂O₃-ZrO₂ powder was used as an additive of alumina ceramic, the coefficient of linear expansion, the folding strength, the compressive strength and the element distribution were respectively measured by high temperature linear expansion instrument, testing machine and energy dispersive spectroscopy (EDS). The results showed that adding zirconia into alumina was propitious to improve the thermal shock resistance and the mechanical property of alumina ceramic.