Aluminate glasses represent a specific group of materials which, in terms of the conventional rules of glass forming and structure, contain no typical glass former. Their structure is also specific, comprising AlOx polyhedral structural units, which can be four-, five-, or six-coordinated, and connected not only through their vortices, but also through their edges and faces. As such, these glasses are rather difficult to prepare, due to their high melting temperatures and high tendency to crystallization, which require specific melting procedures ensuring high cooling rates at the level of 103 K.s-1, and no contact with the walls of melting container to prevent heterogeneous nucleation. For that purpose, we developed a method of flame synthesis of these glasses, one of the few methods facilitating their preparation in technologically relevant amounts. The method yields aluminate glasses of various compositions in the form of microspheres, which can be further used as received, or sintered by viscous flow to obtain bulk glasses, glass-ceramic or ceramic materials.
Viscous flow pressure assisted sintering under strictly controlled conditions and with simultaneous crystallization of aluminate glasses offers an interesting opportunity to prepare Al2O3-Y3Al5O12 and Al2O3-Y3Al5O12-ZrO2 composites with eutectic microstructures at the temperatures up to 1600 ºC, and with interesting mechanical properties (Vickers hardness (HV), 18.1 ± 0.7 GPa and indentation fracture resistance of 4.9 ± 0.3 MPa·m1/2). The composites can be also used as host matrices for optically active elements