Phase Equilibria and Physical Properties of Oxygen-Deficient Zirconia and Thoria |
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Authors: | S C CARNIGLIA S D BROWN T F SCHROEDER† |
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Affiliation: | Refractories Division, Kaiser Aluminum &Chemical Corporation, Center for Technology, Pleasanton, California 94566;Rocketdyne Division, North American Rockwell Corporation, Canoga Park, California 91304 |
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Abstract: | The compositions of anion-deficient zirconia and thoria in equilibrium with O2 were measured from 1 to 10?6 atm and 1400° to 1900°C; for ZrO2- x (po2 in atm, and T in °K), log x~?0.890-(0.400×104)/ T ]-(log p )/6]; for ThO2- x , log x~?1.870-(0.340×104)/ T ]-(log p )/6]. The ZrO2- x -Zr boundary was located at x=0.014 at 1800°C; thoria was single-phase over the entire range. Consistent results were obtained when O2/inert gas mixtures were used, but use of H2/H2O and CO/CO2 at 1000° to 1200°C gave abnormal and, in the latter case, erratic data; side reactions in these atmospheres are inferred. The monoclinic-tetragonal phase change of ZrO2 and the lattice thermal expansion, room-temperature Young's modulus, and strength properties of ZrO2 and ThO2 bodies were not appreciably altered by oxygen deficiency. The lattice dimensions decreased slightly with departure from stoichiometry. |
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