PtTe2: Potential new material for the growth of defect-free TeO2 single crystals

The dissociation of Te–O bonds is the main drawback, which hampers the yield of large-sized paratellurite single crystals of high optical quality when using platinum crucibles. In this work, it is assumed that a catalytic dissociation process involves the intermediate formation of platinum tellurides, these ones being then responsible for entrapment of gas bubbles and black precipitates when growth proceeds. To alleviate this difficulty, we suggest that platinum ditelluride could be a chemically more appropriate compound instead of pure platinum. First experiments on direct transformation of platinum sheets into PtTe2 under tellurium gas atmosphere are described, as well as the procedure used to elaborate a PtTe2 crucible. First seeded Bridgman growth performed in such container yielded a TeO2 single crystal free of defects, thus confirming the validity of our hypothesis about the dissociation process of Te–O bonds.