Ceria (CeO2) is a technologically promising compound due to a remarkable set of properties. However, the use of ceria also has drawbacks, the most pronounced of which is the material's poor thermal stability. This property limits the use of ceria-based materials at elevated temperatures, in many technological applications. To overcome this, the addition of TiO2 is proposed. Such addition essentially creates a new material system, namely Ce1-xTixO2. In this work, an array of techniques were employed to determine the thermal stability of this new compound range (X < 0.2). Results show that when nano-sized, TiO(2 )is fully soluble in CeO2 in this range. After heat treatment, however, the material coarsens and the solubility limit decreases to less than 2 at.%. as the compound undergoes significant changes. These include solute segregation and phase separation. Finally, the factors that affect compound stability are discussed.