Consolidation of Nanograin Ceramics

Improvement in strength is desirable in order to make yttria suitable for transparent window/dome applications. The strength of fine-grain ceramics is limited first by grain size, and second by processing flaws. These strength limiters can be controlled, yielding high-strength and improved transmission by using nanoscale powders and using suitable green-body fabrication techniques and densification schedules. In general, fine grain size in undoped single phase materials is favored by unagglomerated powders; by very uniform "monodisperse" powder particle sizes; by uniform and dense packing (green body fabrication) and by careful control of microstructure by controlled heat treatment schedules that favor densification over grain-growth. Individual technologies have previously been demonstrated to yield some of these process control improvements. However, they have not yet been connected to create an overall process that will repeatably produce high quality components with fine grain size. In this program, we will integrate these approaches to process and consolidate nanoscale yttria precursor powders into transparent components with submicron particle size. The resulting samples are expected to yield improved strength and transmission compared to traditionally fabricated yttria.