STABILITY OF α-ALUMINA PHOTONIC STRUCTURES FORMED AT LOW TEMPERATURES UTILIZING CHROMIA-SEEDING

摘要

Emerging applications of ordered, macroporous oxide photonic structures for thermal barrier coatings, structural coloration, and thermophotovoltaics requires the stability of these features at operating temperatures. However, in high-temperature environments (>1000 °C), these structures can exhibit significant undesired microstructural changes (phase changes, sintering, grain growth, etc.) that result in a loss of the desired properties. An approach for lowering the formation temperature of a-alumina in such structures was demonstrated by seeding with chromia by secondary infiltration from precursor solutions. Seeds of α-chromia, which formed at 500 °C, successfully lowered the a-alumina formation temperature from 1200 to 800 °C by heterogeneous nucleation. Upon heating to 1200 °C, these chromia-seeds went into solid-solution with the alumina structure. However, in contrast to unseeded structures, the resulting microstructures were prone to grain growth and loss of photonic properties upon heating at 1400 °C.