Research On Fabrication Of Sc₂O₃ Nanopowders And Transparent Ceramics

Sc2O3 powders possess excellent properties and extensive application. Transparent Sc2O3 ceramics which are fabricated with the nanopowders are a sort of highly valuable new functional materials. Nowadays, transparent polycrystalline Sc2O3 ceramics have become the replacing material of single crystal. It could be fabricated for laser ceramics when doped with Yb3+, Nd3+ and other rare earth elements. In this dissertation, the fabrication technics of Sc2O3 nanopowders and transparent Sc2O3 ceramics were studied here.By direct precipitation method with ammonia, precipitation precursor with meshy structure could be synthesized from Sc(NO3)3 and NH3·H2O. The calcined powders yielded a weak aggregation for large volume shrinkage of the precursor on drying.By direct precipitation method with hexamethylenetetramine, precipitation precursor with the structure of floccule can be synthesized from Sc2(SO4)3 and (CH2)6N4. The calcined Sc2O3 powders are highly pure, ultrafine, well dispersed, narrow distribution of particle size and spherical. It creates an advantage to fabricate transparent Sc2O3 ceramics because of excellent powder properties.By homogeneous precipitation method with urea, precipitation precursor with the acicular structure could be synthesized. The calcined Sc2O3 powders have better properties. Washing and drying method has a significant impact on the dispersion property of powders. By applying the distilled water, ethanol, and acetone washing process on the precipitation precursor, and then drying at room temperature, the dispersion of Sc2O3 powders were improved.Microwave heating has more advantage than traditional method. By microwave homogenous precipitation method, precipitation precursor with the spumescent structure could be synthesized. The powders which were calcined in resistance furnace had perfect properties. The powders that were radiated in microwave furnace also had excellent property. And the calcination temperature is further reduced.Transparent Sc2O3 ceramics were fabricated with these powders. Various parameters of powder synthesis, molding technique of body and sintering technology have been studied. The pH value has significant influence on sintering properties of powers which directly affects the ceramic transmittance. The transmittance of transparent ceramics by second sintering is better than only by vacuum. The maximum light transmittance is 61% in the wave length of 190-1100 nm.