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.