Phase equilibria in the Hafnia-Yttria-Lanthana system

The HfO2-Y2O3-La2O3 System was studied in the wide range of temperatures (1 250 degrees -2800 degreesC) and concentrations by methods of X-ray analysis at 20 degreesC, petrography, differential thermal analysis in helium at te mperatures to 2500 degreesC, thermal analysis in air using a solar furnace at temperatures to 3000 degreesC, and electron microprobe X-ray analysis. T he complete phase diagram was constructed. The liquidus and solidus project ions, crystallization paths for the alloys, isothermal (1250 degrees, 1600 degrees, and 1900 degreesC) and polythermal sections are presented. The str ucture of the boundary binary systems defines the phase equilibria in the t ernary system. No ternary compounds were found. Ternary solid-solution regi ons were determined based on constituent oxides and intermediate phases.