Synthesis, vaporization and thermodynamic properties of superfine yttrium aluminum garnet

The study of high temperature behavior of Y 3 Al 5 O 12 is urgently required for development of high temperature materials of the new generation including ultra-high temperature ceramics. The superfine Y 3 Al 5 O 12 powder was obtained by the glycol-citrate method; the aggregation process of the sample synthesized was investigated under calcination conditions at different temperatures. Using the Knudsen effusion mass spectrometric method vaporization processes and thermodynamic properties of Y 3 Al 5 O 12 as well as of the melts in the Y 2 O 3 -Al 2 O 3 system were studied at temperatures higher than 2270 K. The simultaneous transition to the gaseous phase of both Al 2 O 3 and Y 2 O 3 from the melt under study was observed during isothermal keeping of the Y 3 Al 5 O 12 sample at the temperature 2675 K with the predominant alumina removal. Analysis of the values of the thermodynamic properties obtained in the Y 2 O 3 -Al 2 O 3 system showed negative deviations from ideal behavior despite the possibility of existence of the miscibility gap at the temperature 2675 K.