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Features of YAG crystal obtaining by Czochralski method using Mo crucibles
|Pavel Arhipov , Sergey Tkachenko , Mikhail Biatov , Oleg Sidletskiy , Sergey Vasyukov|
Institute for scintillation materials of NAS of Ukraine (ISMA), Lenin avenue, 60, Kharkov 61158, Ukraine
Rare-earth doped Y3Al5O12 (YAG) crystals are widely used as laser elements, scintillators, phosphors, etc. Ir crucibles and equipment is a substantial component of crystal cost at growth of high melting point crystals, for ex. by the Czochralski method. Obtaining of high-quality YAG crystals without using Ir is a relevant task. There are some experiments on YAG growth from Mo crucibles described in literature, however, characteristics of the obtained crystals are not so high owing to presence of admixtures and formation of coloration centers.
This work is devoted to possibility estimation of high-quality YAG crystal growth by the Czochralski method using Mo crucible, graphite-based heat insulation, and induction heating in Ar growth atmosphere. It is shown that YAG quality depends on quantity of admixtures and structure defects, which, in turn, are determined by growth conditions and atmosphere. Mechanism of Mo admixture trapping into melt and its impact on optical characteristics are determined; methods decreasing its concentration in crystals are elaborated. Carbon influence at melt stoichiometry and formation of coloration centers is estimated, and solutions providing decrease of its concentration are proposed.
YAG crystals with 30mm diameter and 150 mm length were grown, and their optical and luminescent characteristics (transmission, X-ray luminescence, photoluminescence spectra, thermoluminescence curves) were studied. Optimized conditions of post-growth annealing suppress formation coloration centers and provide crystal absorption ~2 cm-1 in visible band and < 5 см-1 in UV band. These parameters are not worse than those in crystals grown using Ir crucibles. The obtained results show a possibility to obtain high-quality YAG-based crystals by Czochralski method without using high-cost Ir.
Presentation: Poster at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 6, by Pavel Arhipov
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17
Submitted: 2013-03-28 11:34 Revised: 2013-03-30 18:35