Microstructural study of silica-doped zirconia ceramics

The aim of this study was to show the effects of small silica additions on the microstructures and mechanical properties of 3 mol% yttria-stabilised zirconia (3Y-TZP) ceramics. Experiments were conducted on different batches of 3Y-TZP (pure to 2.5 wt% silica-doped). Microstructures were characterised mainly by transmission electron microscopy (TEM), but also by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Silica was found at triple junctions, but neither at grain boundaries nor in the lattice. Undoped zirconia ceramics exhibited faceted grains and significant internal stresses, while doped zirconias showed a much more rounded microstructure and a lower level of internal stresses. Low-temperature degradation (LTD) and slow crack growth (SCG) measurements were conducted on the different batches. The addition of silica strongly increases LTD resistance without affecting the SCG behaviour. The microstructural origins of the different behaviours are discussed. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.