Aluminum titanate (Al2TiO5) is a promising engineering material because of its low thermal expansion coefficient, excellent thermal shock resistance, good refractoriness, and nonwetting with most metals. However, it is susceptible to thermal dissociation in the temperature range of 800 degrees-1280 degrees C, which degrades its desirable properties. In this work, the various factors controlling the thermal instability of Al2TiO5 in the temperature range of 20 degrees-1100 degrees C have been characterized by neutron diffraction to study the temperature- and time-dependence structural changes in real time during the process of thermal decomposition. Results show that the thermal stability of Al2TiO5 is strongly influenced by temperature, dwell time, heating rate, phase purity, grain size, atmosphere, and additives. Possible mechanisms of structure stabilization and instability in Al2TiO5 under different conditions are discussed.