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Czochralski grown large diameter Li2MoO4 single crystals |
| Olga Barinova , Svetlana Kirsanova , Andrey P. Sadovskiy , Igor C. Avetissov |
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D.I.Mendeleyev University of Chemical Technology of Russia (MUCTR), Miusskaya sq. 9, Moscow 125047, Russian Federation |
| Abstract | ||
| Molybdenum containing crystals are known as effective materials for cryogenic phonon-scintillating detectors and widely used for 100Mo 2β decay investigations and dark matter search [1]. The most perspective detectors so called «active» detectors allow realizing the generation of rare nuclear event and its registration in the same crystal. Materials for them have predominantly scheelite-type structure (CaMoO4, CdMoO4), high light yield at the low temperature, but all of them have long-lived radioactive isotopes (48Са,116Cd) entangles neutrinoless 2β decay searches.
Recent observation of possible molybdenum containing materials for cryogenic phonon-scintillating detectors gets clear applicability of Li2MoO4 crystals: they had absence of long-lived lithium isotopes, adequate light yield at low temperatures, high intrinsic radiopurity [2, 3], rather low melting point, but were not large and had а lot of intrinsic impurities and defects. More over the question of existence of phase transitions at atmospheric pressure wasn’t clear [4, 5] In the present research large transparent Li2MoO4 crystals were grown by Czochralski technique, their structure were investigated by XRD, Raman and IR- spectra, by chemical etching. Li2MoO4 was obtained from stoichiometric mixture Li2CO3 and MoO3 by solid-state synthesis technique with subsequent recrystallization from aqueous solutions. Synthesis was carried out at 723 K for 2 h and at 893 К for 4 h. It was noticed that applying of Al2O3 crucible due to interaction between Al2O3 and MoO3 leads to contamination of Li2MoO4 powder by orange inclusions of LiAl(MoO4)2. Transparent crystals with up to Ø25x60 dimensions were grown by the Czochralski technique with 4 mm/h pooling rate (Fig.1).
Fig.1. Li2MoO4 single crystal grown by Czochralski technique and Ø25х1 mm plate cut from the crystal The crystals corresponded to R3 (phenacite-type structure) space group: a=14,32±0,02 Å , c=9,56±0,03 Å / The crystal density derived from XRD data (3.06± 0.01g/cm3) was slightly different from the hydrostatic density (3.03± 0.01g/cm3). It was found out that Li2MoO4 crystals had no MoO42-complexes distortion. Raman spectra had shown differences for || с oriented and ⊥c oriented crystal spectra (Fig.2).
[1] V.B.Mikhailik, H.Kraus. J.Phys.D: Appl.Phys. 39 (2006) 1181-1191 | ||
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Presentation: Poster at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 7, by Igor C. AvetissovSee On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17 Submitted: 2013-04-06 11:38 Revised: 2013-07-18 20:57 |
Fig.2. Raman spectra of Li2MoO4 single crystals cut along: 1 - ⊥c, 2- || с