It has been shown that cesium oxoferrate (VI) decomposes in oxygen at 500 °C giving solid CsxFeIVO2+0.5x (x1.0). The oxidation state of iron has been confirmed by Mössbauer spectroscopy data (single symmetrical resonance line with LW=0.4 (1) mm s–1 and isomr shift of 0.15 (2) mm s–1). Cesium oxoferrate (IV), CsxFeO2+0.5x, crystallizes in the face-centered cubic system with the lattice parameter of a=8.36–8.46 Å and has a crystal structure derived from perovskite.
Authors:Z. Rzączyńska, A. Ostasz, M. Sikorska-Iwan, H. Głuchowska, E. Olszewska, and S. Pikus
of yttrium(III) and lanthanides(III) with 1,2,4,5-benzenetetracarboxylic acid
were prepared as crystalline solids of the general formula Ln4(C10H2O8)3⋅14H2O. They
are insoluble in water. On heating in air or inert gas atmosphere all compounds
lose water molecules; next anhydrous compounds decompose to oxides. The yttrium
complex and heavy lanthanide (from Ho to Lu) ones crystallize in monoclinic
crystal system. The dehydration does not change the crystal structure of the
Authors:T. Sakuma, Xianglian, S. Siagian, K. Basar, H. Takahashi, N. Igawa, and O. Kamishima
Neutron diffraction measurements have been performed on powder VSe at 294 K. The diffuse scattering theory including correlation
effects among thermal displacements of atoms is applied to background function in the Rietveld analysis. The oscillatory scheme
of the diffuse scattering intensity from hexagonal VSe is explained by the correlation effects among far-neighboring Se–Se
atoms. The values of the correlation effects depend on the inter-atomic distance and not on the crystal structure. The relation
between correlation effects and force constants is discussed.
Authors:M. Navarro, M. Lagarrigue, J. De Paoli, R. Carbonio, and M. Gómez
In order to investigate the formation of the multiferroic BiFeO3, the thermal decomposition of the inorganic complex Bismuth hexacyanoferrate (III) tetrahydrate, Bi[Fe(CN)6]·4H2O has been studied. The starting material and the decomposition products were characterized by IR spectroscopy, thermal analysis,
laboratory powder X-ray diffraction, and microscopic electron scanning. The crystal structures of these compounds were refined
by Rietveld analysis. BiFeO3 were synthesized by the decomposition thermal method at temperature as low as 600 °C. There is a clear dependence of the
type and amount of impurities that are present in the samples with the time and temperature of preparation.
The aim of the present study was to determine the kinetic equations for the thermal transformations of precipitated iron oxides
and hydroxides, namely for the process of thermal dehydroxylation of goethite and consecutive of hematite crystal structure
growth as well as for the oxidation of magnetite to maghemite and its thermal transformation into crystalline hematite. The
investigations have been carried out using thermogravimetry (TG/DTG/DTA), X-ray powder diffractometry (XRD) and high temperature
powder diffractometry (HT-XRD). This presentation contains the continuation of our earlier works.
Authors:J. Shao, Y. Yang, B. Li, L. Zhang, Y. Chen, and X. Liu
Two compounds of antimony trichloride and bismuth trichloride with valine are synthesized by solid phase synthesis at room
temperature. Their compositions, determined by element analysis, are Sb(C5H10O2N)3·2H2O and Bi(C5H10O2N)2Cl·0.5H2O. The crystal structure of antimony complex with valine belongs to triclinic system and its lattice parameters are: a=0.9599 nm, b=1.5068 nm, c=1.9851 nm, α=92.270, β=95.050, γ=104.270. The crystal structure of bismuth complex with valine belongs to monoclinic system
and its lattice parameters are: a=1.6012 nm, b=1.8941 nm, c=1.839 nm, β=99.73°. The far-infrared spectra and infrared spectra show that the amino group and carboxyl of valine may be
coordinated to antimony and bismuth, respectively, in two compounds. The TG-DSC results also reveal that the complexes were
Authors:Leszek Rycerz, Ewa Ingier-Stocka, and Marcelle Gaune-Escard
Systematic trends in the thermodynamic properties of congruently melting M3CeBr6 compounds (molar enthalpies of the solid–solid phase transitions, molar heat capacity) following those found for another
M3LnX6 compounds (Ln = lanthanide; X = halide, M = Li, Na, K, Rb, Cs) were evidenced. These data were complemented by electrical
conductivity measurements over the wide temperature range. The results obtained clearly show that the M3CeBr6 compounds can be divided into two groups. The first one with K3CeBr6 compound having a single high temperature modification of cubic, elpasolite-type, crystal structure, and the second one with
Rb3CeBr6 and Cs3CeBr6 compounds having both low- (monoclinic, Cs3BiCl6-type) and high-temperature (cubic, elpasolite-type) modifications. Transition from low- to high-temperature modification
of these compounds is non-reconstructive phase transition. Within the two groups, the thermodynamic and transport properties
of M3CeBr6 compounds are well correlated with their crystal structure. These results suggest different order–disorder mechanisms of
the alkali metal cations whereas the CeBr6 octahedra, forming anionic sublattice, retain their normal lattice positions.
The results of theoretical analysis of the electronic and crystal structural properties and bonding in relation to thermal
decomposition process in anhydrous calcium oxalate are presented. The methods used in this analysis—topological analysis of
electron density (Bader’s Quantum Theory of Atoms in Molecules approach) obtained from DFT calculations performed by Wien2k
package (Full Potential Linearized Augmented Plane Wave Method); bond order model (Cioslowski&Mixon), applied to topological
properties of the electron density; as well as Brown’s Bond Valence Model (bonds valences and strength’, and bond and crystal
strains, calculated from crystal structure and bonds lengths data) are described. The analysis of the obtained results shows
that these methods allow us to explain the way of thermal decomposition process of anhydrous calcium oxalate to calcium carbonate
as a decomposition product, and to describe the structural transition taking place during such process (from monoclinic anhydrous
CaC2O4 to rhombohedral calcite structure). In the light of the results of our similar calculations performed previously for other
anhydrous oxalates (zinc, cadmium silver, cobalt, and mercury) the proposed theoretical approach can be considered as promising
and reliable tool, which allow analyzing the properties of the structure and bonding and hence predicting the most probable
way of thermal decomposition process for given crystal structure.
Authors:D. Giron, Ch. Goldbronn, M. Mutz, S. Pfeffer, Ph. Piechon, and Ph. Schwab
Manufacturing processes may involve the presence of water in the crystallization of the drug substance or in manufacturing
or in the composition of the drug product through excipients. Dehydration steps may occur in drying, milling, mixing and tabletting
processes. Furthermore, drug substances and drug products are submitted to different temperatures and relative humidities,
due to various climatic conditions giving rise to unexpected hydration or dehydration aging phenomena. Therefore the manufacture
and the characterization of hydrates is part of the study of the physical properties of drug substances.
Several hydrates and even polymorphic forms thereof can be encountered. Upon dehydration crystal hydrates may retain more
or less their original crystal structure, they can lose crystallinity and give anamorphous phase, they can transform to crystalline
less hydrated forms or to crystalline anhydrous forms.
The proper understanding of the complex polyphasic systemhydrates–polymorphs–amorphous state needs several analytical methods.
The use of techniques such as DSC-TG, TG-MS, sorption-desorption isotherms, sub-ambient experiments, X-ray diffraction combined
with temperature or moisture changes as well as crystal structure and crystal modelling in addition to solubilities and dissolution
experiments make interpretation and quantitation easier as demonstrated with some typical examples.
Authors:P. Storoniak, K. Krzymiński, A. Boużyk, E. Koval'chuk, and J. Błażejowski
The enthalpies and temperatures of melting and sublimation of acridin-9(10H)-one, 10-methylacridin-9(10H)-one, 2,10-dimethylacridin-9(10H)-one,
10-methyl-2-nitroacridin-9(10H)-one, 10-ethylacridin-9(10H)-one and 10-phenylacridin-9(10H)-one were measured by DSC. Enthalpies
and temperatures of volatilisation were also obtained by fitting TG curves to the Clausius-Clapeyron relationship. Complementary
investigations for anthracene showed the extent to which the thermodynamic characteristics thus obtained compare with those
determined by means of other techniques. For compounds whose crystal structures are known, experimental enthalpies of sublimation
correspond reasonably well to crystal lattice enthalpies predicted theoretically as the sum of electrostatic, dispersive and
repulsive interactions. Analysis of crystal lattice enthalpy contributions indicates that dispersive interactions always predominate.
Interactions are enhanced in acridin-9(10H)-one where intermolecular hydrogen bonds occur: this is reflected in the relatively
high enthalpy of sublimation.