Aluminum titanate (Al2TiO5) is drawing extensive attention because of its unique properties. Al2TiO5 possesses a low thermal expansion coefficient (TEC) of about 1 × 10− 6 K− 1, together with a high melting temperature (1860°C). Such properties allow Al2TiO5 to act as an excellent thermostable, fireproof material for many high-temperature applications, such as casting tools and crucibles for the casting and melting of metallic systems [1–4]. Preparation of Al2TiO5 through a solid-state reaction produced orthorhombic crystals with the following parameters: a = 3.591, b = 9.429, and c = 9.636 [5, 6].
Many methods have been adopted for the preparation of Al2TiO5 ceramics. These include the sol–gel , atmospheric plasma spray (APS) , spark plasma sintering (SPS) , melt synthesis , impregnation [11, 12], and precipitation and co-precipitation methods .
Nano Al2TiO5 was prepared at a low temperature via the sol–gel technique using titanium tetrabutoxide (Ti(OC4H9)4), aluminum chloride (AlCl3), and citric acid monohydrate as a chelating agent . A previous study  adopted the sol–gel technique with phase secession to prepare monolithic Al2TiO5. Polyethylene oxide (PEO) and formamide (FA) were found to dominate the phase secession and gel formation. The usage of adequate quantities of PEO and FA permitted the formation of an Al2TiO5 xerogel that had a monolithic structure with a continual macroporosity exceeding 60%. Heat treatment of the dried gel at 1300°C produced Al2TiO5 as the only present phase.
The solid-state reaction technique was adopted to manufacture Al2TiO5-based ceramics. The starting materials were aluminum sludge (industrial waste) and rutile ore. Findings showed that the presence of MgO, SiO2, Fe2O3, ZrO2, and CaO played a large role as stabilizing oxides that led to the production of Al2TiO5 ceramics with excellent properties .
Azarniya et al.  fabricated Al2TiO5 powder and nanofibers via citrate sol–gel-assisted electrospinning. They showed that the presence of citric acid encouraged the Al3+ and Ti4+ ions to form atomic clusters and to turn them up to nanosized grains during the calcination operation. The lower the citric acid–metal cation ratio, the higher the quantity of crystallized nuclei, which in turn would lead to a smaller grain size. Moreover, firing at temperatures higher than 900°C led to the decomposition of Al2TiO5 into rutile and alumina, and complete degradation occurred at 1050°C.
The nonhydrolytic sol–gel (NHSG) technique was used during linear self-assembly of starting materials to prepare Al2TiO5 fibers. Introduction of stabilizing ions (Mg and Fe ions) could form Mg-O-Ti, Fe-O-Ti, Mg-O-Al, and Fe-O-Al bonds, which enhanced the formation of Al2TiO5 at a low temperature of about 750°C. Simultaneously, introduction of the Mg and Fe ions into the Al2TiO5 lattice enhanced the stabilization of the formed phase. The produced Al2TiO5 fibers possessed unique properties. They had low thermal expansion and high resistance to hot salt melt corrosion .
Al2TiO5 ceramics with high resistance to crack propagation were prepared from alumina and titania co-doped with Mg2+ and other ions, such as Y3+, La3+, and Nb5+. Sintering of the samples co-doped with MgO + La2O3 at 1500°C produced bimodal Al2TiO5 grains. Sintering at such a high firing temperature produced a glassy phase that was responsible for the formation of elongated grains. The produced elongated grains enhanced the mechanical strength through crack propagation resistance. The authors claimed that the grain length growth caused an increase in the estimated length of the frontal process zone and the grain pull-out, bridging, crack deflection, and crack branching mechanisms. Moreover, the co-doping of MgO + Y2O3 resulted in bending strength lower than that obtained from MgO + La2O3. This regression in the bending strength of the samples was due to their granular microstructure. Finally, MgO-Nb2O5 co-doping resulted in ceramic samples with bad mechanical properties. The reason was that large rectangular grains formed because of the liquid-phase sintering .
A previous study reported that doping with MgO, Fe2O3, or SiO2 as a sole additive improved the mechanical properties and decreased the TEC of Al2TiO5 ceramics prepared from α-alumina and TiO2 via a solid-state reaction. Co-doping of MgO with Fe2O3 or SiO2 enhanced the densification parameters and mechanical properties of samples fired for 3 h. In the case of co-doping with MgO + SiO2, MgAl2O4 and Mg2SiO4 might form. These newly formed phases would enhance the stability of the Al2TiO5 by increasing the Al2TiO5 lattice constant (c). Furthermore, co-doping with MgO + Fe2O3 improved the thermal shock resistance of the produced bodies, but its effect on the mechanical properties was limited . Some authors claimed that modulation of Al2TiO5 ceramics prepared via a solid-state reaction with MgO, SiO2, Fe2O3, or their combinations can only prevent the decomposition of Al2TiO5, hence stabilizing the Al2TiO5 structure [17, 18]. In a recent study, the authors proved that the addition of MgO, Fe2O3, and their combination enhanced the formulation of elongated grains and grain boundary microcracks. Such elongated grains tend to interconnect, thus hindering crack diffusion and improving mechanical properties .