Low-temperature isothermal sintering and microstructural characterization of nanocrystalline zirconia ceramics using small angle neutron scattering

Nanocrystalline powders of zirconia, yttria and alumina were synthesized by Inert Gas Condensation and Chemical Vapor Condensation. Compacted samples of pure ZrO2 and dispersion mixed ZrO2 + 14 wt. % Al2O3 and ZrO2 + 9 wt. % Y2O3 were pressureless sintered in vacuum at 1100 degrees C (approximate to 0.4 T-m) for 1, 2, 4 and 10 hours. Nearly full densities have been achieved in all of the three compositions with average grain sizes not exceeding 100 nm. Very small grain sizes of zirconia (< 30 nm) have been found for the composite due to a homogeneous distribution of alumina-phase particles hindering grain coarsening by pinning of the grain boundaries. Complementary to X-ray diffraction and scanning electron microscopy, the microstructural evolution of the n-ceramics was investigated by small angle neutron scattering. Irregularities during the densification of monoclinic zirconia were verified by the scattering curves and attributed to effects due to phase transformation. From the quantitative analysis of the scattering data pore-size-distributions of the materials were obtained. (C) 1999 Acta Metallurgica Inc.