THEORETICALLY DENSE AND NANOSTRUCTURED CERAMICS BY PRESSURELESS SINTERING OF NANOSIZED Y-TZP POWDERS

Nanosized yttria-doped tetragonal polycrystalline zirconia (Y-TZP) pow der was prepared by the coprecipitation method using isopropanol solut ions of organic and inorganic precursors. A isopropanol-washing step l ed to a powder mainly constituted by very soft agglomerates with 6 nm crystallite size. Such a weakly agglomerated powder compacted uniforml y (average diameter pore size = 6 nm) with a homogeneous shrinkage to full density. The small particle size of the Y-TZP powder, the small p ores in the green compacts, and its homogeneous pore size distribution led to theoretically dense and nanostructured (<100 nm) Y-TZP bodies by pressureless sintering at 1000 degrees C for 80-100 h or at 1070 de grees C for 2 h, in spite of the relative low green density (similar t o 43% theoretical). Comparatively, a commercial powder consisting of s pherical weak agglomerates resulted in a fully densified ceramic but a t higher sintering temperature (>1200 degrees C) and with a grain size higher than 0.25 mm. (C) 1997 Elsevier Science S.A.