Preparation Of Ultrafine Zirconia Powders

Ultrafine zirconia powders were prepared by the calcinations of the amorphous hydrous zirconia precursor powders obtained by coprecipitating zirconyl subcaronate and followed by n-butanol azeotropic distillation process using ZrOCl2 and YCl3 as raw materials and NH4HCO3 as a precipitant. The form and constitution of the zirconyl subcarbonate were determined via TG-DTA,IR spectra and related chemical analysis. The effects of precipitating process conditions on the precipitation form of products and the properties of zirconia powders obtained were studied and the optimum process conditions for the manufacture of zirconia precursor powders were determined. The changes of the thermochemical behaviours, phase structure , particle size, morphology and BET specific surface area of precursor powders in the process of calcinations were investigated, and TG-DTA, XRD, TEM, IR spectra, nitrogen adsorption and some other experiment methods have been employed to characterize the products. In addition, the sintering behavior of the zirconia powders calcined at 950C was also studied after uniaxially dry-pressing of the powders at 15-16 Mpa. The research results show:(1)Ultrafine zirconia powders, with particle sine in the range 25~30nm can be prepared by calcinating at 1000C for 2h the precursor powders , which was obtained by n-butanol azeotropic distillation of the wet zirconyl subcarbonate precipitates synthesized under the conditions of reactions temperature 20~30C, ZrOCl2 concentration 0.5 mol L , NH4HCO3 concentration 0.5mol L and PEG (200 ,1540,6000) addition 0.35%(2)The sequence of phase transformation of the zirconia precursor powders during calcinating was found to be amorphous ZrO2 ZrO(OH); 400C amorphous ZrO2 400C monoclinic ZrO2 >800C tetragonal ZrO2.(3)The yttria-stabilized zirconia(YSZ) powders can be obtained by calcinating the precursor at the temperature >400C. The particle size of the YSZ powder was increased with raising calcinations temperatures.(4)The specific surface area of the YSZ powders was decreased gradually during the calcinating process. The specific surface areas of tetragonal YSZ powders obtained at 600C and 1000C were 92.5 m2/g and 28.0 m2/g respectively.(5)The tetragonal YSZ powders obtained at 950C can be sintered to 98.52% relative density at 1450C for 3h.