It is feasible to add homogeneously minute amounts (0.25 wt%) of Al2O3 into 3 mol% yttria stabilized tetragonal zirconia polycrystals using a co-precipitation procedure to produce precursory gel nano-powders. X-ray diffraction, scanning electron microscopy, high-angle annular dark-field-field emission gun transmission electron microscopy, relative density determination, shrinkage, and resistivity measurements using impedance spectroscopy were combined to elucidate the microstructure and sintering behavior of zirconia ceramics produced using 0.25 wt% added Al2O3, possibly the limit of solubility of Al2O3 in the ZrO2 structure. Two modes of sintering behavior may be described as: (I) The total solid solution of Al2O3 in the solid solution of ZrO2 structure via a precursory co-precipitation procedure; calcining at 800 oC and sintering at 1275 oC can be shown to indicate the viable solubility of Al2O3 in the ZrO2 structure, designated as stage I of the thermal treatment; and (II) At the higher sintering temperature, above 1275 oC, the segregation of Al2O3 at triple junction occurs. Higher bulk and grain boundary resistivity values are found for the sample sintered at 1275 oC, which probably resulted from the dissolution of Al2O3 in the ZrO2 structure.