Comparative study on the solid-state reaction synthesis of Y-Al-O system ceramics by Y₂O₃-Al₂O₃ powders

Phase transformations of powders with varying mole ratios n(Y₂O₃):n(Al₂O₃)=2:1, 1:1, 3:5 calcined under different temperatures and their ceramics sintered under high temperature were investigated. The Y₂O₃-Al₂O₃ system was characterized by the differential thermal analyzer-thermogravimetry, X-ray diffraction and scanning electron microscopy. The results show that no reaction occurs in the Y₂O₃-Al₂O₃ system below 800 °C, and Y₄Al₂O₉ (YAM) phase appears after calcination at 1 000 °C, YAlO₃ (YAP) and yttrium aluminum garnet (YAG) phases are shown after calcination at 1 200 °C. The Y₂O₃-Al₂O₃ system with n(Y₂O₃):n(Al₂O₃)=3:5 is transformed into YAG single phase after calcination at 1 400 °C. Ceramics prepared in the Y₂O₃-Al₂O₃ system with n(Y₂O₃):n(Al₂O₃)=2:1 and 3:5 are YAM and YAG phases and their relative volume density values are 97.8% and 99.95%, respectively. Multiphases coexist in ceramics prepared in the Y₂O₃-Al₂O₃ system with n(Y₂O₃):n(Al₂O₃)=1:1. The fracture morphologies of the three ratios of ceramics vary widely.