Dynamics neutron diffraction study of self-recovery in Aluminium Titanate

Aluminium titanate (Al2TiO5) is an excellent refractory and thermal shock resistant material due to its relatively low thermal expansion coefficient and high melting point. However, Al2TiO5 is only thermodynamically stable above 1280 degree Celsius and undergoes a eutectoid decomposition to -Al2O3 and TiO2 (rutile) in the temperature range of 900-1280 degree Celsius. In this paper, we describe the use of high-temperature neutron diffraction and differential thermal analysis to study the properties of self-recovery in Al2TiO5 when it is annealed at 1300 degree Celsius in air. It is shown that the process of decomposition in Al2TiO5 is reversible and that self-recovery occurs readily when decomposed Al2TiO5 is re-heated above 1300 degree Celsius. It is further shown that the existence of a temperature range (900-1280 degree Celsius) in which Al2TiO5 is prone to decomposition can be explained by the competing dominance of self-recovery at 1280 degree Celsius and decomposition at 1280 degree Celsius. Subsequent decomposition of reformed Al2TiO5 during cooling below 1200 degree Celsius is governed by the temperature-dependent atomic diffusion rates. (author)