Abstract Zirconia-based solid electrolytes are among the best known oxygen-ion conductors. During the last few decades, efforts have been made to understand the behavior of transport properties in stabilized zirconia. Recent investigations show that defect interactions, defect clustering and ordering, and microdomain formation all play an important role in the transport properties of stabilized zirconias. Further investigation is, however, required to understand the effect of defects, their interaction and ordering on transport, and related properties of stabilized zirconia systems. A degradation in properties due to aging phenomena in stabilized zirconias has been found. Recent studies reveal the presence of phases CaZrO 3 and CaZr 4O 9 in aged stabilized zirconia. In the present investigation, our main interest is in examining the formation and stability of the phases CaZrO 3 and CaZr 4O 9 in calciastabilized zirconia. We studied the energetics of these phases and calculated the relaxed ionic coordinates by atomistic computer simulation techniques.