Model of two-step sintering conditions for yttria-substituted zirconia powders
authors Lourenco, MA; Cunto, GG; Figueiredo, FM; Frade, JR
nationality International
journal MATERIALS CHEMISTRY AND PHYSICS
author keywords Ceramics; Sintering; Microstructure; Electrical conductivity
keywords CONSTANT GRAIN-SIZE; STABILIZED ZIRCONIA; TAGUCHI METHOD; CERAMICS; ELECTROLYTES; DENSE; MICROSTRUCTURE; CONDUCTIVITY; NANOCERAMICS; FABRICATION
abstract A method is described to assess optima two-step sintering schedules of ceramic materials that combines predictions of the sintering kinetics based on shrinkage data with Taguchi fractional experimental plans. The study is based on commercial nanopowders (similar to 50 nm) of the partially stabilized tetragonal zirconia (ZrO(2))(0.97)(Y(2)O(3))(0.03), and the fully stabilized cubic phase (ZrO(2))(0.92)(Y(2)O(3))(0.08). The controlled processing parameters are the peak temperature (T(p)), the temperature and dwell time of the isothermal step (T(d) and t(d)) and the cooling rate (beta) between T(p) and T(d). Dense (ZrO(2))(0.97)(Y(2)O(3))(0.03) ceramics were obtained with an average grain size of similar to 100 nm under the conditions T(p) = 1320 degrees C, T(d) = 1250 degrees C, t(d) = 12 h and beta = 20 K min(-1). Grain growth is inhibited to a lesser extent for the (ZrO(2))(0.92)(Y(2)O(3))(0.08) ceramics, with the lowest average grain size of 450 nm obtained for T(p) = 1320 degrees C, T(d) = 1270 degrees C, t(d) = 12 h and beta = 20 K min(-1). The predictions based on Herring's scaling law applied to non-isothermal densification data are in reasonable agreement with isothermal results obtained for the tetragonal zirconia ceramics, whereas they fail for the cubic phase, probably due to the grain growth occurring up to T(p). The total ionic conductivity values at 1000 degrees C are 0.0525 cm(-1) for (ZrO(2))(0.97)(Y(2)O(3))(0.03) and 0.145 S cm(-1) for (ZrO(2))(0.92)(Y(2)O(3))(0.08). These values are comparable to those reported for samples with three to four times larger grain size. (C) 2010 Elsevier B.V. All rights reserved.
publisher ELSEVIER SCIENCE SA
issn 0254-0584
year published 2011
volume 126
issue 1-2
beginning page 262
ending page 271
digital object identifier (doi) 10.1016/j.matchemphys.2010.11.028
web of science category Materials Science, Multidisciplinary
subject category Materials Science
unique article identifier WOS:000287349600042
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