Subsolidus Phase Equilibria and Ordering in the System ZrO2-Y2O3 |
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Authors: | CARMEN PASCUAL PEDRO DURÁN |
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Affiliation: | Instituto de Cerámica y Vidrio, C. S. I. C., Departamento de Materiales Cerámicos Especiales, Arganda del Rey, Madrid, Spain |
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Abstract: | The subsolidus phase relations in the entire system ZrO2-Y2O3 were established using DTA, expansion measurements, and room- and high-temperature X-ray diffraction. Three eutectoid reactions were found in the system: ( a ) tetragonal zirconia solid solution→monoclinic zirconia solid solution+cubic zirconia solid solution at 4.5 mol% Y2O3 and ~490°C, ( b ) cubic zirconia solid solutiow→δ-phase Y4Zr3O12+hexagonalphase Y6ZrO11 at 45 mol% Y2O3 and ~1325°±25°C, and ( c ) yttria C -type solid solution→wcubic zirconia solid solution+ hexagonal phase Y6ZrO11 at ~72 mol% Y2O3 and 1650°±50°C. Two ordered phases were also found in the system, one at 40 mol% Y2O3 with ideal formula Y4Zr3O12, and another, a new hexagonal phase, at 75 mol% Y2O3 with formula Y6ZrO11. They decompose at 1375° and >1750°C into cubic zirconia solid solution and yttria C -type solid solution, respectively. The extent of the cubic zirconia and yttria C -type solid solution fields was also redetermined. By incorporating the known tetragonal-cubic zirconia transition temperature and the liquidus temperatures in the system, a new tentative phase diagram is given for the system ZrO2-Y2O3. |
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