Sintering behavior and mechanical properties of injection-molded zirconia powder

Compared to normally continuous sintering at 1500 degreesC for 30 min, a novel two-stage sintering by firing the sample at 1500 degreesC for 5 min and then rapidly cooling down to 1300 degreesC for 10h was proposed to investigate sintering behavior and mechanical strength of injection-molded yttria-stabilized zirconia (Z3Y). The injection-molded Z3Y feedstocks were prepared from the mixture of Z3Y powder and organic polymers with different solid content from 75 to 82 wt.%. The effect of sintering process on the microstructure evolution, physical characteristics and mechanical strength of molded Z3Y samples was investigated. It was found that bulk density and mechanical strength increases with solid content from 75 up to 82 wt.% in both sintering processes. X-ray diffraction (XRD) analysis shows that the industrial Z3Y samples consist of monoclinic and tetragonal phase, and the relative intensity ratio of tetragonal to monoclinic phases is almost independent of sintering process. Experimental results further demonstrate that a denser microstructure with finer grains was obtained with the two-stage sintering. Enhancement of bending strength (1078 MPa) due to the two-stage sintering process by a factor of four times in comparison with that (295 MPa) fired with normal sintering process has been obtained in the injection-molded Z3Y with the solid content of 82 wt.%. The enhanced bending strength is primarily attributed to more dense and fine-grain microstructure but not to tetragonal phase effect. Similar enhanced effect is also applied for the tetragonal zirconia polycrystals (TZP). (C) 2003 Elsevier Ltd and Techna Group S.r.l. All rights reserved.