Processing and Sintering of Ultrafine MgO‐ZrO₂ and (MgO, Y₂O₃)‐ZrO₂ Powders

Abstract

Chemical coprecipitation was used to prod~~ce ultrafine and easily sinterrMc MsogcpbiliVa and (Mg0,Y203)stabilized Zr02 porrders. The sintering behavior is very sensitive to post-precipitation washing because Yhard" agglomerates form when the precipitated gels are washed with water, whereas "soft" agglomerates form when they are washed with ethanol. The soft agglomerates pack oniformly, resnlting in hshrinkage of powder compacts to neartheoretical density. The hard agglomerates result in compacts which have regions of l d i z e d densification and a signifiint fraction of residual porosity. [

Dry pressing boehmite gels for the fabrication of monolithic α-Al2O3

“…This result differs from Readey et al, who reported that green densities between water-dispersed and ethanol-dispersed ZrO2 powders differed by 3.5% after pressing at 70 MPa, i.e., the ethanol-dispersed ZrOa had a 40% green density and the water-dispersed ZrOa was 36.5% dense [21].…”

“…The higher sintered densities achieved in water-dispersed system for short sintering time is due to a higher agglomerate density, and consequently faster kinetics of intraagglomerate densification. In the work of Readey et al [21], the ethanol-dispersed sample with a higher green density showed similar densification behavior to the water-dispersed samples. That means the lower green density of water-dispersed system did not result in retarded densification kinetics at low temperature sintering.…”

Synthesis by coprecipitation of india-stabilized zirconia and codoping with MoO3, WO3, TaO2.5, or NbO2.5 for application as thermal barrier coatings

“…4b, whereas the lower S BET values after FD is a direct effect of the formation of hard agglomerates. For both EW/AD and FD powders, the electron diffraction patterns show tetragonal zirconia 45,46 , along with the interplanar spacing of 0.29 nm for the (101) t plane, once again consistent with the values reported for tetragonal symmetry 47,48 .…”

Azeotropic distillation, ethanol washing, and freeze drying on coprecipitated gels for production of high surface area 3Y–TZP and 8YSZ powders: A comparative study

“…Nonetheless, these advantages are largely offset by the formation of hard agglomerates, which persists as a serious drawback of coprecipitated YSZ powders [14]. Hard agglomerates are formed by strong intercrystallite bonding during removal of the surface hydroxyl groups at the www drying stage, and are consolidated in the calcination step by the following reaction [15][16][17]:…”