Ceramics like yttrium aluminum garnet from Y2O3-Al2O3, mostly remain amorphous and difficult to crystallise. Although this system is studied well about phase transformation and possibilites to retain amorphous nature are still investigated. Going into ternary composition for this system is possible in terms of properties of interest.

Amorphous ceramics in powder form can be synthesized by various chemical routes and they are widely reported. However, converting those amorphous powders into a dense, amorphous bulk form is not always easy. In most cases, combination of high pressure and temperature results in crystallization (or at least partial crystallization).

I am listing some of the reports on bulk dense amorphous solids belongs to Y2O3-Al2O3 and ZrO2-Al2O3 systems

http://onlinelibrary.wiley.com/doi/10.1111/j.1551-2916.2005.00502.x/abstract

http://onlinelibrary.wiley.com/doi/10.1111/j.1151-2916.1999.tb02131.x/abstract

http://www.sciencedirect.com/science/article/pii/S1359645402000587

http://onlinelibrary.wiley.com/wol1/doi/10.1111/j.1551-2916.2007.01913.x/abstract

Another method is to use aerodynamic levitation and CO2 laser heating system to melt the refractory materials, e.g. Y2O3, ZrO2, Al2O3, and TiO2. Beside the high tempature of ~2200 to 2500 oC, It also can provide the high quenching rate to make them amorphourize. It could be a good way to study the isssue of glass nature and glass transition.