Effect of nanostructuring on thermal stability and decomposition of aluminium titanate (Al2TiO5): A phase transformation study

Abstract

As a refractory ceramic, the thermal instability of aluminium titanate (AT or Al2TiO5) has been in the crosshairs of research works in recent years. The studies have indicated that different parameters such as atmosphere, grain size, additives, oxygen pressure, and synthesis method can bilaterally affect the thermal decomposition of AT ceramic and resultant physicomechanical properties. In the present study, the AT nanostructure was synthesized by a citrate sol-gel method and influence of nanostructuring nature on its thermal instability and reaction pathway was explored in some details. It was shown that the reduction of grain size down to 30 nm can destabilize AT, so that the reaction starts from the threshold temperature of around 300 °C instead of 900 °C. This significant reduction in reaction temperature was attributed to the increase of interfaces density and crystallographic imperfections, serving as preferential sites for starting the thermal dissociation. However, the nanostructuring is not able to change the temperature spectrum in which a vast majority of AT ceramic is dissociated with a strong kinetics (i.e. 1100 °C). It was confirmed that the thermal instability of AT nanostructure bears a slow kinetics, so that a heat treatment at 1200 °C for 5 h cannot completely decompose this ceramic.