Characterization of mullite-zirconia composites prepared from various starting alumina phases

Abstract

Zirconia-dispersed mullite composites were prepared by reaction sintering of boehmite, γ-alumina, (δ+θ)-alumina and α-alumina as sources, mixed with zircon powder. The powder mixtures

were ball-milled and isostatically pressed into disks. The obtained samples were sintered between

1400 and 1600°C for 2h in air. The resulting sintered materials were characterized in terms of bulk

density, dilatometry, DTA/TG, XRD and SEM. From the dilatometric and differential thermal analysis

curves, several microstructural transformations which occur in these samples are detailed in this work.

XRD peaks suggested fully developed mullite and zirconiaphases by reaction sintering of zircon and

all alumina phases. Zircon usually dissociates attemperature higher than 1665°C. However, it is

shown in this study that zircon dissociates at about1400°C due to the presence of transition alumina

phases. The microstructure of all the composites is composed of irregularly shaped mullite grains, and

round-shaped zirconia grains which are distributed intragranularly and intergranularly.