Electronic Polarisability of NaNO2–NaNO3 and NaOH–NaNO3 Ionic Melts and Effective Ionic Radius of OH－

Molar volumes and refractive indexes of molten NaNO2–NaNO3 and NaOH–NaNO3 systems were measured by dilatometry and goniometry, respectively. The molar volumes of both systems increased with increasing temperature. Refractive indexes decreased with a rise of temperature or with increasing wavelength of the incident visible light. Assuming that the electronic polarisability is inherent in an ion, the electronic polarisability of a OH－ ion in the melt was estimated from the Lorentz–Lorenz equation to be 1.26×10−30 m3, being comparable with that in the crystal. The effective ionic radius of a OH－ ion was evaluated from the obtained electronic polarisability to be 1.34×10−10 m, using the correlation between the third power of the ionic radius and the electronic polarisability of an ion so far reported. The effective ionic radius obtained in this work was in good agreement with that assigned by Shannon.

Study on Lanthanide Oxides Materials in Material Engineering with a New Method

In material engineering, the higher charge number of an element in a compound, the more strongly its atom attracts electrons. Hence, the polarizability is entirely different when it is in different valence states. Moreover, most elements are able to exercise more than a single coordination number in a given oxidation state. On the basis of ionization potential and effective ionic radius, some empirical expressions were proposed to predict the electronic polarizability and optical basicity of lanthanide oxides for the different coordination numbers (6-12). The estimated values are in perfect agreement with previously reported values in the literature. This work provides a simple and effective method to predict the electronic polarizability and optical basicity of lanthanide oxide

Structures of 6H perovskites Ba3CaSb2O9 and Ba3SrSb2O9 determined by synchrotron X-ray diffraction, neutron powder diffraction and ab initio calculations

The structures of the 6H perovskites Ba3 B 2+Sb5+ 2O9, B = Ca and Sr, have been solved and refined using synchrotron X-ray and neutron powder diffraction data. Ba3CaSb2O9 and Ba3SrSb2O9 have monoclinic C2/c and triclinic P\bar 1 space-group symmetries, respectively, while Ba3MgSb2O9 has ideal hexagonal P63/mmc space-group symmetry. The symmetry-lowering distortions are a consequence of internal `chemical pressure' owing to the increasing effective ionic radius of the alkaline-earth cation in the perovskite B site from Mg2+ (0.72 Å) to Ca2+ (1.00 Å) to Sr2+ (1.18 Å). Increasing the effective ionic radius further to Ba2+ (1.35 Å) leads to decomposition at room temperature. The driving force behind the transition from P63/mmc to C2/c is the need to alleviate underbonding of Ba2+ cations in the perovskite A site via octahedral rotations, while the transition from C2/c to P\bar 1 is driven by the need to regularize the shape of the Sb2O9 face-sharing octahedral dimers. Ab initio geometry-optimization calculations were used to find a triclinic starting model for Ba3SrSb2O9.

Effect of chlorine on the crystal structure of a chlorine-rich hastingsite

The structure refinement of a hastingsite (Cl 0.91 p.f .u.) from West Ongul Island, Ltitzow-Holm Bay, East Antarctica, has been carried out in order to characterise the effect of CI on the crystal structure. The composition of the Cl-rich hastingsite is K0.69Na0.26Ca1.99Mg1.09Fe2+2.71Fe3+0.92Mn0.04Ti0.10−Al2.31Si5.83O22OH0.99Cl0.91F0.10 with unit cell parameters a 9.962(3), b 18.283(7), c 5.572(1) Å and β 104.87(3)°.In the Cl-rich hastingsite, A1, Fe3+ and Ti occupy only the M(2) site, and Fe2+ strongly prefers the M(1) and M(3) sites to the M(2) site with respect to Mg. The Mg-Fe2+ distribution suggests that the Mg-CI avoidance is realised in the intracrystalline exchange reaction among the octahedral sites in the Cl-rich hastingsite. The individual position of CI and OH was refined and the effective ionic radius of Cl in fourfold coordination is determined as 1.79 Å. Substitution of Cl for OH expands the sizes of the M(1) and M(3) sites and extends the double chains in comparison with hydroxy calcic amphiboles. Cl especially, is close to the 0(6) and 0(7) oxygens beyond the minimum distance calculated from effective ionic radii. Therefore, the Cl-rich hastingsite is considered to be deformed locally by Cl.

Bindung von Thallium(I) durch Hexacyanoferrate(II) / Binding by Hexacyanoferrates (II) of Thallium (I)

The salts of FeIII, CoII, and NiIII form precipitates with Na4- or K4 [FeII(CN)6], the so-called mixed hexacyanoferrates (II) (HCF). Experiments with radioactive tracers (24Na, 42K, 59FeIII, 60CoII, 59FeII(CN),4⊖, and 204TlI) have shown that the composition of HCF depends on the nature as well as on the initial concentration of the metal ions involved and can be described by the general formula ExMzR·n E Y. Ε stands for univalent cations (e.g. H⨁, Na⨁, K⨁, Tl⨁, and others more), M for a heavy metal ion, R for Fe(CN)64⊖, and Y for anions (e. g. Cl⊖, SO42⊖, OH®). The mixed HCF are cation- and anion-exchangers, the equilibrium between solid and liquid phase depending on the nature and concentration of cations and anions in both phases. The binding stability of cations increases proportionally to the effective ionic radius: H⊕<Na⊕<K⊕<Tl⊕. Because of its favourable ionic radius, Tl⊕ exhibits a high affinity towards the mixed HCF and can be separated from solution with a high efficiency.