Mechanochemical synthesis of yttrium and lanthanum tantalates

The phase changes in the Y2O3-Ta2O5 and La2O3-Ta2O5 systems during mechanical activation and subsequent heat treatment are investigated. Y2O3 and Ta2O5 are shown to react during mechanical activation to form Y3TaO7. Calcination of activated mixtures leads to the formation of YTaO4 and LaTaO4. The observed processes are interpreted in terms of transformations of the fluorite structure. A new method is proposed for the synthesis of rare-earth tantalates for applications in diagnostic x-ray contrast media. The method has a number of important advantages over the conventional ceramic route.