PHASE-DIAGRAM OF NONSTOICHIOMETRIC 10 MOL-PERCENT GD2O3-DOPED CERIUM OXIDE DETERMINED FROM SPECIFIC-HEAT MEASUREMENTS

The phase diagram for nonstoichiometric 10 mol% Gd2O(3)-doped cerium o xide, Ce0.818Gd0.182O1.909-y, was determined from specific heat measur ements in the temperature range 300-1250 K and composition range Ce0.8 18Gd0.182O1.909-Ce0.818Gd0.182O1.731, using a controlled diabatic scan ning calorimeter. No phase transition was found in this temperature ra nge for the composition Ce0.818Gd0.182O1.909. The specific heat measur ements reveal phase transitions for the composition range Ce0.818Gd0.1 82O1.859-Ce0.818Gd0.182O1.731. A phase diagram is constructed which sh ows a miscibility gap. The maximum of the miscibility gap occurs at th e composition Ce0.818Gd0.182O1.788 and T = 939 K. The phase diagrams o f nonstoichiometric CeO2-x, and Ce0.818Gd0.182O1.909-y are compared an d discussed in detail. (C) 1995 Academic Press, Inc.