Effect of powder calcination conditions on IR transmission in Y₂O₃-MgO nanocomposites fabricated by pulsed electric current sintering technique

In order to improve IR transparency of the Y₂O₃-MgO composite, the effect of powder calcination conditions was investigated. The absorption intensity of carbonate peaks sensitively changes with the powder calcination conditions, such as temperature and time, before the pulsed electric current sintering (PECS). The calcination at 1150℃ for 8 h can eliminate the contamination of the carbonate groups pre-existing in the starting Y₂O₃ and MgO powders. The composites fabricated from the powders, which were calcinated at the optimum conditions, can attain high IR transparency with maintaining the fine and dense microstructures. This indicates that the pre-calcination of the powders is an effect method to remove the carbonate contamination without causing significant powder coarsening and agglomeration in the Y₂O₃-MgO composites. During the PECS processing, however, a small amount of carbon contaminations occurs additionally from the graphite die/paper and remains even in the post-annealed Y₂O₃-MgO composite. It can be concluded that for the Y₂O₃-MgO composites, although the carbonate related contaminations are succeeded to remove from the starting power mixture, the carbon contamination occurs additionally from the graphite die/paper during the PECS processing and degrades the IR transparency. (author)