Phase Diagram of Nonstoichiometric 10 mol% Gd2O3-Doped Cerium Oxide Determined from Specific Heat Measurements

Abstract The phase diagram for nonstoichiometric 10 mol% Gd 2 O 3 -doped cerium oxide, Ce 0.818 Gd 0.182 O 1.909- y , was determined from specific heat measurements in the temperature range 300-1250 K and composition range Ce 0.1818 Gd 0.182 O 1.909 -Ce 0.818 Gd 0.182 O 1.731 , using a controlled diabatic scanning calorimeter. No phase transition was found in this temperature range for the composition Ce 0.818 Gd 0.182 O 1.909 . The specific heat measurements reveal phase transitions for the composition range Ce 0.818 Gd 0.182 O 1.859 -Ce 0.818 Gd 0.182 O 1.731 . A phase diagram is constructed which shows a miscibility gap. The maximum of the miscibility gap occurs at the composition Ce 0.818 Gd 0.182 O 1.788 and T = 939 K. The phase diagrams of nonstoichiometric CeO 2- x and Ce 0.818 Gd 0.182 O 1.909- y are compared and discussed in detail.