Crystal structure of octapotassium octasulfatodiceriate pentahydrate
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CTURE OF INORGANIC COMPOUNDS
Crystal Structure of Octapotassium Octasulfatodiceriate Pentahydrate L. F. Malakhovaa, O. A. Alekseevaa, N. G. Furmanovaa, S. N. Bocharovb, and L. Yu. Kryuchkovab a
Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, 119333 Russia email: [email protected] b St. Petersburg State University, St. Petersburg, 199034 Russia email: [email protected] Received August 10, 2009
Abstract—Single crystals without Co and Ni have been crystallized by the substitution method in the K2Ni(SO4)2–Ce(SO4)2–H2SO4–H2O system using K2Co(SO4)2 ⋅ 6H2O, K2 (Co,Ni)(SO4)2 ⋅ 6H2O, or K2Ni(SO4)2 ⋅ 6H2O as protocrystals. The structure of the single crystals obtained has been established by Xray diffraction analysis. The crystal structure contains dimer complex anions [Ce2(μSO4)2(SO4)6]8–, K+ cations, and crystallization water molecules. DOI: 10.1134/S1063774510020069
INTRODUCTION In terms of searching for methods for doping tran sitionmetal sulfate crystals and for impurities affect ing the spectra of optical crystals, we attempted to syn thesize the K2(Co,Ce)(SO4)2 ⋅ 6H2О and K2(Ni,Ce)(SO4)2 ⋅ 6H2О crystalline phases in the CeSO4 ⋅ 4H2O–K2Ni(SO4)2 ⋅ 6H2O–K2Co(SO4)2 · 6H2O–H2SO4–H2O and CeSO4 · 4H2O–NiSO4 ⋅ 7H2O–K2Co(SO4)2 ⋅ 6H2O–H2SO4–H2O systems. The data on the solubility and composition of Cecon taining crystalline phases and their properties are absent in the literature; therefore, experiments on the interaction between crystals and solutions in a wide range of change in their compositions are the most informative.
of the Ni and Co components. A decrease in the con centration of potassium ions in the solution does not change the crystallization scheme but only delays the onset of deposition of the first crystal portions. The Xray diffraction powder pattern of the K2(Co, Ni)(SO4)2 · 6H2О crystals that were grown is almost identical to the diffraction pattern of the wellknown K2Ni(SO4)2 · 6H2O and K2Co(SO4)2 · 6H2O phases (ICPDF, nos. 210632, 350632) [1]. Thus, the Xray diffraction analysis of the crystals grown from K2(Ni,Со)(SO4)2 + Се(SO4)2 + H2SO4 aqueous solu tions with different ratios of the Ni, Co, and Ce com ponents shows that cerium does not enter the structure of K2(Ni,Co)(SO4)2 ⋅ 6H2O crystals.
EXPERIMENTAL Growth and XRay Diffraction Analysis of Crystals Crystallization was performed using direct growth from solution by decreasing the temperature through the exchange (substitution) reaction of the phases. The ratios of the starting reagents in the preparation of watersalt mixtures were chosen empirically. During the growth from solution, it is the Сe(SO4)2 ⋅ 4H2О and K2Ce(SO4)3 phases that are the first to crystallize due to their relatively low solubility. The removal of К+ ions from the solution leads to a significant expansion of the stability ranges for Ni and Co salts in the solution. The latter begin to crystallize only after the significant evaporation of the solvent and the complete removal of Ce ions from the solu tion. Further crystalliz
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