Sintering and compensation effect of donor and acceptor codoped 3 mol% Y₂O₃-ZrO₂

Addition of 0.15-0.5 mol% acceptor oxide, Al₂O₃, to 3 mol% Y₂O₃-ZrO₂ results in enhanced densification at 1350°C. The enhancement is accounted for by a liquid phase sintering mechanism. While the addition of donor oxide, Ta₂O₅, of 0.15-2.5 mol% at 1300-1600°C results in the decrease of final density and in the destabilization of the tetragonal (t) phase of the 3 mol% Y₂O₃-t-ZrO₂ (TZP). X-ray diffractometry (XRD) reveals that the Ta₂O₅-added 3 mol% Y₂O₃-ZrO₂ contains monoclinic (m) ZrO₂ phase and a second Ta₂Zr₆O₁₇ phase. The decrease is attributed to the increase of m-ZrO₂ content in these samples. Complete phase transformation from t-ZrO₂ to m-ZrO₂ observed in samples added with 2.5 mol% Ta₂O₅ is interpreted by the compensation effect based on donor and acceptor codoping defect chemistry.