NEUTRON-DIFFRACTION STUDIES OF PHASE-TRANSFORMATIONS BETWEEN TETRAGONAL AND ORTHORHOMBIC ZIRCONIA IN MAGNESIA-PARTIALLY-STABILIZED ZIRCONIA

Neutron powder diffraction and conventional dilatometry have been used to investigate the tetragonal‐to‐orthorhombic phase transformation and the orthorhombic‐to‐tetragonal reversion in a high‐toughness magnesia‐partially‐stabilized zirconia. For this material, the onset temperature on cooling for the tetragonal‐to‐orthorhombic transformation (determined by dilatometry) was 192 K, and the reversion on subsequent heating occurred between 500 and 620 K. Neutron diffraction patterns were recorded at temperatures down to 19 K then up to 664 K, and analyzed by the multiphase Rietveld method to determine the amounts of different phases as well as their lattice parameters and unit‐cell volumes. It is notable that, at its maximum, the orthorhombic phase amounted to 45% of the sample by weight. Length changes were measured, using pushrod dilatometers, in the temperature range 80 to 700 K. Length changes calculated from the neutron diffraction determinations of the proportions and unit‐cell volumes of the different phases are in very good agreement with the directly measured values. Copyright © 1990, Wiley Blackwell. All rights reserved