Cadmium tungstate CdWO4 (CWO) is scintillator widely studied and used in spectrometric and radiometric devices, X-ray computed tomography and cargo inspection. Zinc tungstate ZnWO4 (ZWO) is similar to CWO but is non-toxic while CWO is. Though ZWO has smaller light output, it may replace CWO in some cases applications. A wide using of ZWO is limited because it is not produced on an industrial scale. The main problem complicating the growing of ZWO is its tendency to cracking [1].

The largest of the previously created CWO single crystals with the weight up to 10 kg, size up to 80 mm in diameter and height 200 mm were grown along [001] direction in the Nikolaev Institute of Inorganic Chemistry SB RAS (NIIC) by the Low thermal gradient Czochralski technique (LTG CZ). Research and development puller HX620 with crucible 140 mm in diameter and height 300 mm were used [2].

The aim of this work is further development of LTG CZ method capability and increasing of CWO and ZWO single crystals sizes. For growing of large CWO and ZWO crystals by the LTG CZ production puller GRAN-4/140 was developed. As a prototype puller HX780 [2] designed at NIIC was used and adopted for working with toxic charge. The GRAN‑4/140 puller has doorless lift opening camera. Auxiliary upper chamber is used to separate the crystal from the seed after the process. The three zone resistive heater enables using of crucibles up to 140 mm in diameter. The puller GRAN-4/140 is supplied with the crucible weighing cell DSHT-026 having maximal load 50 kg and weighing range 25 kg. Input signal processing and control actions are provided by PLK100 controller (ARIES). Software package InduSoft Web Studio™ is used as HMI/SCADA system.

In the development of the process of obtaining of isotopically enriched CWO crystals [3, 4] growth along the [010], has been successfully implemented. This experience was applied to the growth of large ZWO and CWO crystals. The influence of growth conditions on crystal morphology and quality for both types of crystals and different growth directions is discussed. High quality single crystals free of inclusions were grown with a fully rounded interface or flat interface formed by [010] face. Melt losses due to evaporation were less then 0.5 wt%. The utilization of the charge was better then 80%.

Optical and scintillation characteristics of grown crystals are reported.

[1] Sangeeta, S.C. Sabharwal. J. Crystal Growth 310 (2008) p. 2899

[2] A.A. Pavlyuk, Yu.G. Stenin. SCINT-1999. Abstracts book, p. 147.

[3] Ya.V. Vasiliev, Yu.A. Borovlev, E.N. Galashov, et al. Stcintilliatcionnye materialy. Inzheneriya, ustroistva, primenenie. Kharkiv: ISMA (2011) pp. 119–180.

[4] E.N. Galashov, V.A. Gusev, V.N. Shlegel et al. Crystallography Reports 54, (2009) p. 689.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/29415 must be provided.