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Progress in growth of large CdWO4 and ZnWO4 crystals by the Low-thermal-gradient CZ technique

Alexander P. Chubarev 1Anna G. Postupaeva 1Vasily N. Zhdankov 1Yuri A. Borovlev 2Olga E. Safonofa 2

1. Crystal Manufacturing Lab (CML), Lavrentev 3, Novosibirsk 630090, Russian Federation
2. Institute of Geology and Mineralogy SB RAS (IGM), Koptyuga ave., 3, Novosibirsk 630090, Russian Federation


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.


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Presentation: Poster at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 6, by Anna G. Postupaeva
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-04-04 06:18
Revised:   2013-04-04 06:59