CRYSTALLIZATION AND THERMAL-PROPERTIES OF AL2O3-Y2O3 MELTS

The density and thermal expansion of yttrium aluminum garnets and yttr ium aluminum perovskite were studied in liquid and solid states over t he temperature range 1850-2450 K by irradiating the samples with a nar row beam of gamma quanta. Density changes on equilibrium and nonequili brium crystallization were investigated and the temperatures of phase transition and concentration of metastable eutectic also were found. I t was shown that structural changes and phase separation of the garnet melts are lacking when these are heated above melting temperature. It was found that the specific volume (cm(3)/g) of the melts in the Al2O 3-Y2O3 system linearly depends on the weight concentration (%) of the yttrium oxide V(2350 K) = 0.3446 - 1.345 x 10(-3) C and that their the rmal expansion coefficient (TEC) agreed with TEC of pure alumina withi n the measurement error.