Characterization of Y_2O_3, CeO_2 and Y_2O_3+CeO_2 Doped FGM Tetragonal ZrO_2 Ceramics by Spark Plasma Sintering

摘要

In this study, 2 mol% Y_2O_3 (2Y), 1 mol% Y_2O_3+6 mol% CeO_2 (lY6Ce) and 12 mol% CeO_2 (12Ce)-doped tetragonal ZrO_2 ceramics were made by spark plasma sintering (SPS) for 2 min at 1450℃ under a pressure of 60 MPa. The influence of stabilizers on microstructure, phase and mechanical properties of the ZrO_2 ceramics was investigated. After sintering, the 2Y and lY6Ce were intact, containing full tetragonal ZrO_2 phase on the polished cross-sectioned surface, whereas the 12Ce exhibited macro-cracks, corresponding to a large amount of monoclinic ZrO_2 phase. Graded microstructure and mechanical properties were observed in the 1 Y6Ce, showing a gradually decreased fracture toughness from sample edge towards centre, together with the slight decreased hardness. The 2Y had a uniform microstructure and mechanical properties. The formation of the graded structure and toughness profile was explained in terms of the gradual CeO_2 reduction to in the Y_2O_3+CeO_2 doped ZrO_2 ceramics.