ABSTRACT
The non-crystalline state of solids exhibits many intriguing characteristics. While silicate glasses have been used and studied for centuries, other glassy or amorphous materials are of relatively recent origin. Examples of such materials are metallic glasses,
chalcogenide glasses, polymeric glasses, and non-silicate amorphous oxides. The last class of amorphous materials is often dificult to obtain experimentally and therefore our understanding of their structure and properties is lagging behind those of other non-crystalline materials. Alumina forms the base for some of the interesting non-silicate amorphous materials. While multicomponent glassy materials, containing small additions of silica and titania are easier to obtain and study, binary alumina-base oxide glasses (e.g., Al2O3-ZrO2 and Al2O3-Y2O3) are more dificult to obtain and possess limited thermal stability. The challenges in processing and characterization of these materials have been overcome through non-conventional approaches. Interesting properties have been identiied, the most exciting one being the discovery of large-scale plasticity in these materials. The amorphous phases in these alumina based binary materials crystallize into phases with excellent mechanical and optical properties. These phases are nanocrystalline with sizes below about 50 nm. Therefore a processing technique of producing bulk nanocrystalline oxides opens up as advances are made in producing bulk glasses in the irst place.
