Nanostructured and near defect-free ceramics by low-temperature pressureless sintering of nanosized Y-TZP powders

Abstract

Nanosized (∼6 nm) Y-TZP (3 mol% Y2O3) powders have been produced by chemical co-precipitation (Y-inorganic + Zr-organic precursors) and thorough isopropanol-washing step, after calcining in air at 450 °C. The nanocrystalline Y-TZP powders consisted of spherical soft agglomerates (∼100 nm in size) which were easily broken down during compaction resulting in a very uniform green microstructure with a narrow pore size distribution (average pore size less than 6.5 nm) and no detectable compacting defects. In spite of the relatively low green density (43% theoretical), Y-TZP powder compacts sintered to near theoretical density in the very low-temperature range of 1000 °C for 80–100 h to 1070 °C for 2 h, maintaining a grain size in the nanoscale (< 100 nm) and the sintered bodies were nearly defect-free. Hardly any grain growth took place up to 1000 °C; it was very rapid above this temperature.