Bridgman growth of paratellurite single crystals

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

“…As a matter of fact, we have already pointed out [9] that coupled SEM and microprobe analysis performed on numerous inclusions exhibited always the coexistence in much diversified proportions of three elements only, namely Pt, Te and O, and no other one. Thus it appears that these defects are not correlated to an eventual presence of some impurities in the starting raw materials, which are high-purity TeO 2 powder (99.9995%) and pure platinum (99.9%).…”

“…Today, both fields of application require a yield of crystals of large dimension, along with a uniform and best level of crystalline perfection. Since the earliest attempts [6], numerous works have been carried out for this purpose, mainly based on using the pulling or so-called Czochralski method [7,8], the Bridgman one being also proposed recently [9,10]. Whatever the technique employed, the growth of crystals is performed from pure TeO 2 powder melted in a platinum crucible, despite a clear evidence of a chemical interaction between the liquid phase of TeO 2 and the Pt container.…”

“…A detailed description of defects observed in Bridgman grown crystals has been given in a previous paper [9]: SEM and microprobe analysis evidenced the presence of platinum in black inclusions, while micro-Raman spectroscopy allowed assessing oxygen as being the gas content of occluded bubbles. As in the case of Czochralski grown crystals, such drawback may be overcome to some extent through a careful control of the growth parameters like pulling and rotation rates, as well as thermal gradients over the crystal-melt interface [14].…”

“…Since metallic platinum was found as small aggregates scattered in the TeO 2 matrix, we have suggested that Pt could be regarded as catalyzing the dissociation of Te-O bonds [9]. Originated at the crucible wall, it further generates the formation of oxygen gas bubbles of various sizes in the melt.…”

Growth of the high quality and large size paratellurite single crystals

“…However, by this method, TeO 2 crystals tend to crack and their diameters increase uncontrollably during the crystal pulling. Bridgman technique has also been used to prepare paratellurite single crystals [14,15]. However, it is very difficult to grow large size and high quality TeO 2 single crystals.…”