Preparation And Characterization Of Singlephase And Multiphase Y₂O₃, ZrO₂, Al₂O₃ Nanometer Powders

Al₂O₃-ZrO₂-Y₂O₃ ceramics hassuperior mechanical properties and broad applicationprospect, which is the hotspot in the recent ceramic materials' research. The advancementand development of nanometer technology have expanded the research fields of ceramicmaterials. In order to obtain high performance nanocomposites ceramic materials, theagglormeration of nanometer particles should be overcomed; the reaction sequence andfinal products of the composite powders needs a further research.In thiswork, nanometer Al₂O₃, ZrO₂, Y₂O₃ and Al₂O₃-ZrO₂-Y₂O₃ compositepowders were prepared by chemical precipitation methods, combining severalanti-agglormoration methods. The powders and their precursors were characterized byXRD, TEM, SEM, IR, DLS and other analytical instruments. The influence of precipitant,concentration, solvent, stoichiometry and other factors on the powder size, morphorlogyand phase was studied. The results show that the chemical composition and properties ofthe precursor have a great effect on the agglormeration. Ammounium carbonate doublesalt precursors of the cation could be obtained with appropriate amount ammouniumbicarbonate as precipitant. Nanometer Al₂O₃, ZrO₂ powders with spherical morphologyultrafine size, narrow distribution, good dispersibility and non-agglormerationcharacteristics were fabricated by calcining the precursors, while Y₂O₃ powder has arhombic platelet structure and micrometer size. The formation process of the specialmorphology and the inherited relationship with its precursor were studied. There aredifferent inflexion points on the sintering curves of amorphous, metastable phase andstable a phase alumina, which correspond to the crystalline, phase transformation andsintering process respectivly. When metastable phase transforms intoα-alumina, a lot ofpores generate, which hinders the densification of sintering.Al₂O₃-ZrO₂-Y₂O₃ composite powders were prepared using different precipitants andmethods. The partical size, phase composition and reaction sequence of the compositepowders were studied. The results show that well dispersed composite powders can beobtained with NH₄HCO₃ as precipitant using drying method. When the compositepowders were annealed at lower temperature, the solid solution reaction between Y₂O₃and ZrO₂ happened firstly, surplus Y₂O₃ showing a single phase, and no reaction betweenY₂O₃ and Al₂O₃ was observed; while at high tempreture, YAG could be obtained withAl₂O₃ and surplus Y₂O₃. The main phase composition of the composite powders, whichcontain relative higher Y₂O₃, are c-ZrO₂,α-Al₂O₃ and YAG.