Synthesis Of Zirconia Powder By Hydrothermal Method And Its Characterization

In this paper,the tetragonal phase and the monoclinic phase zirconia powder were prepared by hydrothermal method using zirconium oxychloride as raw material,ammonia or urea as precipitant,and water as medium,yttrium as stabilizer,glycerol as organic additive,and fluoride as inorganic mineralizer.XRD,SEM,particle size analysis and other characterization methods were used to systematically investigate the effects of hydrothermal temperature,hydrothermal time and pH on the morphology,crystal phase and particle size distribution of zirconia.Results show that the products synthesized under pure water system keep monoclinic and tetragonal mixed phase structures,and the product powders agglomerate seriously.The optimum synthesis conditions under this system are that precursor concentration is 1 mol/L,solution pH value is 10,hydrothermal temperature is 180?,hydrothermal time is 12 h.The tetragonal zirconia powder was synthesized under pure water system with Y as stabilizer.There are no significantly differences on the microstructures of the zirconia powders obtained with and without Y under pure water system.The zirconia powders still maintain the agglomerates assembled by small particles on the surface.The optimum doping amount of Y is 3 wt%.Using glycerol and water as the medium,the main factors affecting the formation of the tetragonal phase are the amount of glycerol and the pH of the solution.When the amount of glycerol is less than 2 wt%,powders with tetragonal phase can be obtained.When the amount increased to more than 4 wt%,the product is in a dispersive amorphous phase.When the solution pH is below 6,the product is a tetragonal and monoclinic mixed phase structure.When the pH is upper or equal 6,the product is a tetragonal phase.The zirconia powders synthesized under the doped F-ion systern are pure monoclinic phase structures.At 180?,3 h,the monodispersed ruthenium-like zirconia powder with primary particle size under submicron can be obtained.As the hydrothermal time prolonged,the zirconia powder gradually grew and eventually evolved into a micron-sized ruthenium-like zirconia powder.