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Rubidium-nickel and cesium-nickel sulphates hexahydrates: new crystals for UV band filters

Vera Manomenova ,  Elena Rudneva ,  Alexey E. Voloshin ,  Vadim Grebenev ,  Natalia L. Sizova ,  Lyudmila F. Malakhova 

A.V.Shubnikov Institute of Crystallography The Russian Academy of Sciences, Moscow, Russian Federation

Abstract

Rb2Ni(SO4)2·6H2O (RbNSH) and Cs2Ni(SO4)2·6H2O (CsNSH) crystals belong to the nickel Tutton salts.

The large single crystals of Rb2Ni(SO4)2·6H2O (RbNSH) and Cs2Ni(SO4)2·6H2O (CsNSH) were grown. Some properties of these crystals were studied such as their structure, transmission spectra, thermal stability.

We determined the solubility curves of these salts in preparation for the crystal growth process. Both crystals were grown from low temperature solutions: by temperature decrease and by the solvent-evaporation techniques. Due to different solubility the normal growth rates were 0.2-0.4 mm/day for RbNSH and 0.5-2.0 mm/day for CsNSH depending on the crystal faces.

The RbNSH structure was refined and CsNSH structure was determined.  RbNSH and CsNSH crystals belong to monoclinic sp.gr. P21/c and form isostructural series with ANSH and KNSH.

Transmission spectra demonstrate rather high transparence in UV band (220-320 nm) that makes them possible for application as UV-filters.

The thermogravimetric measurements were made for both crystals. It was shown that the process of the single crystal dehydratation starts at temperatures 107 ºC for CsNSH and 110 ºC for RbNSH (the sample heating rate was 5 K/min). So these crystals are more thermal stable than well known α-NSH, ANSH and KNSH.

For CsNSH crystal the microhardness of (010), (001) and (100) plates was studied. The distinction in the hardness of different faces indicates the presence of anisotropy of the second kind in these crystals with the anisotropy coefficient k1=1.4.

The internal defect structure of RNSH and CsNSH crystals was studied by X-ray topography. It was shown that growing CsNSH crystals by the solvent-evaporation method preferable.


Due to their good optical and thermogravimetric properties both crystals could be used as material for UV filters

 

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Related papers

Presentation: Poster at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, General Session 2, by Elena Rudneva
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-04-15 16:42
Revised:   2013-04-15 16:47