Metal oxide-zirconia systems are a potential class of materials for use as structural materials at temperatures above 1900 K. These materials must have no destructive phase changes and low vapor pressures. Both alkaline earth oxide (MgO, CaO, SrO, and BaO)-zirconia and some rare earth oxide (Y2O3, Sc2O3, La2O3, CeO2, Sm2O3, Gd2O3, Yb2O3, Dy2O3, Ho2O3, and Er2O3)-zirconia system are examined. For each system, the phase diagram is discussed and the vapor pressure for each vapor specie is calculated via a free energy minimization procedure. The available thermodynamic literature on each system is also surveyed. Some of the systems look promising for high temperature structural materials.
Metal oxide-zirconia systems are a potential class of materials for use as structural materials at temperatures above 1900 K. These materials must have no destructive phase changes and low vapor pressures. Both alkaline earth oxide (MgO, CaO, SrO, and BaO)-zirconia and some rare earth oxide (Y2O3, Sc2O3, La2O3, CeO2, Sm2O3, Gd2O3, Yb2O3, Dy2O3, Ho2O3, and Er2O3)-zirconia system are examined. For each system, the phase diagram is discussed and the vapor pressure for each vapor species is calculated via a free energy minimization procedure. The available thermodynamic literature on each system is also surveyed. Some of the systems look promising for high temperature structural materials. Jacobson, Nathan S. Glenn Research Center...
A collection of Papers Presented at the 28th International Conference and Exposition on Advanced Ceramics and Composites held in conjunction with the 8th International Symposium on Ceramics in Energy Storage and Power Conversion Systems.
Zirconium oxide or Zirconia has a melting point of about 27000, is resistant to chemical attack by acids and bases, is very stable at high temperatures in oxidizing atmospheres, and is inert when in contact with most metals at high temperatures. In addition, zirconia is relatively inexpensive and abundant. These characteristics of zirconia would make it a very satisfactory material for many high-temperature applications, were it not for the fact that pure zirconia undergoes an allotropic transformation from tetragonal to monoclinic on cooling through a temperature range in the neighborhood of 900 C. This transformation takes place with a volume increase of about 3 percent. During the reverse transformation near 11000 C on heating, zirconia shrinks by about the same amount. The large anisotropic volume changes associated with the transformation cause bodies made from pure zirconia to disintegrate during their manufacture or when in use. In practice, this difficulty is circumvented by adding small amounts of certain Oxides, such as calcia, magnesia, yttria, etc., to zirconia. Depending on the kind and amount of oxide added to the zirconia, the high-temperature crystal structure of the combination is totally or partially retained on cooling, and the allotropic transformation is also totally or partially suppressed. This so-called stabilized zirconia performs satisfactorily in many high-temperature applications, but the addition of stabilizing oxides also introduces some undesirable features, such as an increase in the thermal-expansion coefficient, a lowering of the melting point, and, for some types of stabilized zirconia, a tendency to disintegrate on prolonged thermal cycling. A zirconia-base material combining the high-temperature properties of pure zirconia without the disadvantages associated with the use of stabilizers would be highly desirable.
This volume is part of the series on "Chemical Thermodynamics", published under the aegis of the OECD Nuclear Energy Agency. It contains a critical review of the literature on thermodynamic data for inorganic compounds of zirconium. A review team, composed of five internationally recognized experts, has critically reviewed all the scientific literature containing chemical thermodynamic information for the above mentioned systems. The results of this critical review carried out following the Guidelines of the OECD NEA Thermochemical Database Project have been documented in the present volume, which contains tables of selected values for formation and reaction thermodynamical properties and an extensive bibliography. * Critical review of all literature on chemical thermodynamics for compounds and complexes of Zr.* Tables of recommended Selected Values for thermochemical properties* Documented review procedure* Exhaustive bibliography* Intended to meet requirements of radioactive waste management community* Valuable reference source for the physical, analytical and environmental chemist.
