Oxygen Barrier Oxides
Abstract
A series of mixed oxides with composition Zr3M4O12 were prepared as candidate high-melting-point ceramics for composite applications. The oxides selected should have significantly reduced oxygen diffusion coefficients compared to cubic-stabilized zirconia. Colloidal processing and conventional sintering produced samples with densities near 98% of theoretical. Zr3M4O12 compositions with M = Sc, Y, La, and Gd, as well as Y2O3 and cubic-stabilized zirconia, were studied using the 18O-exchange method to measure diffusivity in the range 900 deg -1200 deg C. The materials span about three orders of magnitude in diffusivity, with D ranging from 10-7 to 10-10 CM2/s at 1135 deg C. Zr3Sc4Ol2 and Y2O3 were found to have the lowest diffusivity, and the temperature dependence for all of the rare earth containing ceramics was similar. For the mixed oxides, there is no apparent trend correlating diffusivity and the crystal lattice dimensions. Porous microstructures in some of the materials, especially cubic-ZrO2 and Zr3Gd4Ol2, led to experimental 180-exchange versus time curves which could not be easily fitted to theoretical curves. Doping studies Of SC3+ and Ta 5+ in Zr3La4Ol2 showed no significant effect on diffusivity at 1135 deg C.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1992
- Accession Number
- ADA253683
Entities
People
- Doreen Edwards
- Jill Jonkouski
- Rheal Turcotte
Organizations
- Northwestern University