Phase diagrams and thermodynamics of rare-earth-doped zirconia ceramics*
Chong Wang, Matvei Zinkevich, and Fritz Aldinger
Max-Planck-Institut für Metallforschung and Institut für Nichtmetallische Anorganische Materialien, Universität Stuttgart, Heisenbergstraße 3, D-70569 Stuttgart, Germany
Abstract: Results of the comprehensive experimental and computational phase studies of the systems ZrO2-REO1.5 (RE = La, Nd, Sm, Gd, Dy, Yb) are summarized. Various experimental techniques, X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), transmission electron microscopy (TEM), differential thermal analysis (DTA), and high-temperature calorimetry are employed to study the phase transformation, phase equilibria between 1400 and 1700 °C, heat content and heat capacity of the materials. A lot of contradictions in the literature are resolved, and the phase diagrams are reconstructed. Based on the experimental data obtained in this work and literature, the systems ZrO2-REO1.5 are thermodynamically optimized using the CALPHAD (CALculation of PHase Diagram) approach. Most of the experimental data are well reproduced. Based on the present experiments and calculations, some clear characteristic evolutions with the change of the ionic radius of doping element RE+3 can be concluded.
Keywords: ceramics; rare-earth-doped; phase diagram; CALPHAD; zirconia.
*Paper based on a presentation at the 12th International IUPAC Conference on High Temperature Materials Chemistry (HTMC-XII), 18-22 September 2006, Vienna, Austria. Other presentations are published in this issue, pp. 1635-1778.