Low (and negative) thermal expansion Al2TiO5 materials and Al2TiO5 - 3Al2O3.2SiO2 - ZrTiO4 composite materials. Processing, initial zircon proportion effect, and properties

Abstract

Aluminum titanate (Al2TiO5) materials and aluminum titanate - mullite- zirconium titanate (Al2TiO5 - 3Al2O3.2SiO2 - ZrTiO4) composite materials were successfully processed from fine commercial powders and characterized. This was achieved by zircon (ZrSiO4) addition to stoichiometric alumina - titania mixtures. Zircon addition was the principal processing variable explored. This additive stabilizes the unstable aluminum titanate phase, enhances the sintering process, restricts microcrack development and improves the mechanical properties of the bulk material, but has a slight detrimental effect on its thermal expansion behavior (αapp from −1.5 to 2.5 × 10−6 °C−1 in the RT-800 °C range). With a clear microstructure configuration change, all the technological properties are directly (linearly) correlated with zircon proportion in the initial formulation in the range between 5 and 30 wt%. Developed phases were established, relatively dense ceramics were produced, and complex microstructures with multiphasic interlocked grains were identified. Also, an interconnected microcrack matrix was observed with no material integrity loss which explained the low or even negative thermal expansion behaviors observed in the developed materials. This, together with the mechanical behavior detected, encourages structural applications with high thermomechanical solicitations. The triplex composite material presented an excellent thermomechanical behavior and low porosity, 48 MPa flexural strength, low stiffness and high sintering grade with low thermal expansion.