| Abstrakt: |
1.With the aid of complex thermal and x-ray diffraction analyses, it was established that upon the crystallization of ZrO2 from the amorphous state, the first phase formed is a metastable cubic modification which, upon heating to more than 600°, irreversibly changes into a monoclinic modification.2.The investigation corroborated the existence of the compounds La2Zr2O7, Nd2Zr2O7, and Ce2Zr2O7 with a pyrochlore-type structure. The mechanism of their formation upon heating of the coprecipitated hydroxides was considered. A method of synthesizing cerium zirconate was proposed.3.Cerium zirconate, Ce2Zr2O7, in contrast to the compounds La2Zr2O7 and Nd2Zr2O7, is oxidized upon heating in air and changes into a cubic solid solution of the fluorite type between GeO2 and ZrO2.4.The temperature of the beginning of the interaction of the coprecipitated hydroxides of zirconium and the rare earth elements lies below the crystallization points of the zirconates. The formation of the compound may already begin in the process of coprecipitation or, at any rate, during the dehydration of the coprecipitated hydroxides.5.Some of the physicochemical properties of the zirconates of the rare earth elements were studied. |
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