Densification of Monoclinic ZrO2 with Vanadate Additives

摘要

Sintering of monoclinic XrO2 ceramic powders was carried out < 1150 C using 1-8 wt% V2O5 (or ZrV2O5 equivalent) as flux additive. Densities > 92% ThD were achieved using a relatively coarse commercial (PS approx = 1.5 micrometers) ZrO2 powder with 1.5-2.0 wt% V3Os5 additive by sintering in air at 1100 C for up to 24 hr. High pressed densities were found to be correlated to high fired densities, thus, ZrO2 powders with average particle size < micrometers gave lower densities. Microstructural and chemical analysis of the sintered samples were carried out to determine the composition and a relative distribution of the ZrO2 and intergranular phases. Methods used included: SEM, TEM, X-sray microanalysis (EDAX), EPR, DTA, TGA, and arc emission spectroscopy techniques. Results showed the solubility of vanadium in the ZrO2 phase to be low (approx 0.2 at .%-indicated to be V4+ ions). The bulk of the added vanadium was found in the grain boundary region which together with Ca, Si, and Mg impurities formed the amorphous bonding phase. This indicates densification by reactive liquid phase sintering aided perhaps by defect migration. The optimum combination of density, strength, electrical conductivity, and expansion coefficient was found for a V2O5 content of 1/5 wt%.