ZrO2-Y2O3 3) 4% 4), 5) ZrO2-Y2O3 3) 12) ZrO2-Y2O3 13) ZrO2-Y2O3 2 2 1 Zr1−xYxO2−x/2 x = 0.04, 0.2, 0.3 0.5 0.5mol • dm −3 120 600 900 3 75μm 600 3 1650 5 3 × 0.7 × 30mm X rint 2000 CuKα 40kV 40mA 2 2 MR500 The Internal Friction of Yttria Stabilized Zirconia with Large Amount of Oxygen Vacancy by Masakuni OZAWA and Kenji TSUCHIYA We examined the internal friction (IF) behavior of Y2O3-stabilized ZrO2 with a large amount of oxygen vacancy by using forced torsion method in the temperature range of 25~420. In the polycrystalline Zr1−xYxO2−x/2 (x = 0.3 and 0.5), a single and broad IF peak was observed at around 150~350. The analysis of IF peak suggested that the internal friction was induced by the relaxation of oxygen vacancy in the local structure. Also, the formation of locally immobile coordination of vacancy was suggested by the IF amplitude for heavily defective cubic zirconia.