The effects of preparation method on the characteristics of alumina-zirconia powders

Two series of Al₂O₃-ZrO₂ powders with various contents of ZrO₂ were synthesized by sol-gel (chemical polymerization) and coprecipitation methods. The effect of ZrO₂ content and preparation method on the structure and texture of the resultant powders were determined. The samples were characterized by nitrogen sorption, thermal gravimetric analysis, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. The sol-gel method yields more homogeneous powder and retards the aggregation of particles. It produces powders with a larger surface area, a smaller pore size, and a narrower pore size distribution than the coprecipitated one. The X-ray diffraction results show that the powders are amorphous at the calcination temperature below 700°C for both methods. Incorporation of zirconia into alumina greatly affects the surface properties of the powders upon heating, exerting a protective effect against sintering, and inhibiting both the crystallization of the -Al₂O₃ phase and the - to -phase transformation. Zirconia is dispersed in alumina matrix and does not form a new structure.