Phase formation in the series of Bi3Nd2Fe1 + yTi3 – 2yNbyO15 and Bi3Tb2Fe1 + yTi3 – 2yNbyO15 (y = 0.0–0.6 and Δy = 0.2) samples is studied. When Bi3Nd2Fe1 + yTi3 – 2yNbyO15 solid solutions (ss) are doped with niobium(V) ions, the formation of Bi3Nd2FeTi3O15 layered perovskite, a member of the Aurivillius phase family of general formula Am – 1Bi2BmO3m + 3 (m = 4), is not dominant in samples where y ≥ 0.2. Bi4Ti3O12 (m = 3) and NdFeO3 phases are formed in the course of phase interaction under the chosen conditions. With higher niobium(V) amounts, a Bi2Ti2O7-base pyrochlore ss phase is formed in the Bi3Tb2Fe1 + yTi3 – 2yNbyO15 multicomponent system. Dielectric spectroscopy shows that the phases in samples of both series where y > 0.0 undergo structural alterations associated with magnetic and electric ordering.

Mono-and mixed-ligand complexes with the composition [Ni(Cyt)2(H2O)2]Cl2, [Ni(Thr–)2(H2O)2] and [Ni(Thr–)(Cyt)(H2O)2]Cl are synthesized and studied. Using IR spectroscopy it is determined that in the complex compounds, cytosine is bidentate (C=O group oxygen and heterocycle N3), threonine interacts with the Ni(II) ion due to amino and carboxyl groups. The models of the atomic structure of the studied compounds are proposed based on the EXAFS and XANES spectroscopy results.

The influence of BiFeO3 on phase formation, crystal structure, and dielectric properties of solid solutions close to the Morphotropic Phase Boundary in the (Na0.5Bi0.5)TiO3 - (K0.5Bi0.5)TiO3 TiO3 system was studied. The formation of samples with pure perovskite structure was proved, increase in the unit cell parameters and in the T-m value while decrease in elelctroconductivity and dielectric loss stimulated by the BiFeO3 addition were revealed.

Phase formation, crystal structure parameters, dielectric and ferroelectric properties of ceramic solid solutions in the (1-y)[(1-x)(Na0.5Bi0.5)TiO3-x(K0.5Bi0.5)TiO3]-yBiFeO(3) system with x = 0.25, y = 0 - 0.6 has been studied. Pure samples with the pseudocubic perovskite structure were obtained by the solid state reaction method. Addition of BiFeO3 stimulated a monotonous increase in the unit cell volume and in the Curie temperature T-m value. With increasing the BiFeO3 content, nonmonotonous behaviour of the dielectric permittivity, a decrease in the T-ph value, a decrease in total electroconductivity and dielectric loss at the room temperature were revealed.

Phase formation, structural and electric properties of bismuth layered perovskite like ferroelectric ceramics Sr[Bi1 - xTbx](2)[Nb0.9Fe0.05Cr0.05](2)O9 - delta (1) and Sr[Bi1 - xTbx](2)[Ta0.9Fe0.05Cr0.05](2)O9 - delta (2) have been investigated. It has been determined that single phase solid solutions are formed at 0.00 <= x <= 0.04 (1) and 0.00 <= x <= 0.30 (2). The perovskite-like structure of all solid solutions obtained is characterized by the orthorhombic symmetry. The volume of the unit cell and T-C of solid solutions 1 and 2 has been found to decrease with x increasing. (C) 2012 Elsevier B.V. All rights reserved.

The effect of the cationic composition on the formation of perovskite solid solutions based on bismuth ferrite(Bi1 − x/3□ x/3)[Fe1 − x Ti x ]O3 with x = 0.00–0.48, Δx = 0.03, has been studied. The homogeneity range of the perovskite phase under the conditions of the solid-phase synthesis of solid solutions has been determined, and the effect of the cationic composition on the physicochemical properties of solid solutions has been studied.

Ceramic solid solutions (Bi1-yLay)(4)(V1-xMex)(2)O11-y with x, y < 0.2 Me-Zr, Ga, Fe, Cu, have been prepared by the solid state reaction method. Crystal structure parameters, phase transitions, dielectric and transport properties of ceramic samples have been studied. Concentration and temperature stability regions of monoclinic alpha-, orthorhombic beta- and tetragonal gamma- or gamma'- polymorph modifications have been determined. Annealing of samples, containing large amount of Cu and/or La dopants, at 973 K in the reducing atmosphere resulted in their decomposition, though compositions containing low content of La, Ga or Zr dopants, remained pretty stable. (C) 2010 Elsevier B.V. All rights reserved.

J.N. Torba, N.V. Golubko, E.A. Fortalnova, G.M. Kaleva, M.G. Safronenko, N.U. Venskovskii and E.D. Politovaa,∗ Karpov Institute of Physical Chemistry, Vorontsovo Pole St., 10, 105064, Moscow, Russia Peoples’ Friendship University of Russia, Ordzhonikidze St., 3, 117198, Moscow, Russia Ceramic composites (100− n)Bi4V2O11−z–nCe0.9Gd0.1O1.9 with n = 0÷ 25 wt% were prepared and studied by the X-ray diffraction, dielectric spectroscopy, and impedance methods. Slight increase in the unit cell volume accompanied by monotonous decrease in temperatures and broadening of the α–β and β–γ phase transitions with increasing fluorite content was observed in the composites studied. Increase in melting temperatures of composites with n ≥ 10 with the retention of their high ionic conductivity was also proved.

Phase formation of Bi 4 (V 1 − x Cu x ) 2 O 11 − z solid solutions (BICUVOX) with x = 0.00–0.20 and Δ x = 0.02 was studied. The concentration stability ranges were determined for the α, β, and γ polymorphs of BICUVOX solid solutions at room temperature, and their unit cell parameters were revised. The following was found to occur as x rises: the α ai β phase transition temperature between the monoclinic and orthorhombic phases shifts down, the β ai γ phase transition temperature to the high-temperature tetragonal phase shifts down, and the order-disorder phase transition temperature between γ′ ai γ tetragonal phases shifts up.

Ceramic solid solutions (Bi1-yLay)(4)(V1-xZrx)(2)O11-z with x = 0-0.05, y = 0-0.16 have been prepared by the solid state reaction method. The samples were studied by differential thermal analysis, X-ray diffraction, dielectric spectroscopy, and impedance methods. The concentration and temperature stabilization regions of the polymorphous alpha-, beta-, gamma'-, gamma-modifications have been determined. The effects observed in dielectric properties, conductivity, and impedance data confirmed the influence both of intrinsic oxygen vacancies and those "pinned" at ferroelectric domain boundaries on the temperature hysteresis of alpha-beta phase transition and their contribution to mechanism of oxygen ion transport.

Ceramic solid solutions (Bi1 − y La y )4(V1 − x Me x )2O11 − z (x, y < 0.2: Me = Zr, Ga, Fe, Cu) were prepared by solid-state reaction. It was shown that the annealing (973 K, reducing atmosphere H2/Ar (20/80)) of the samples whose compositions belong to the stability domains of α, β, and γ′ polymorphs increases their electronic conductivity by six orders of magnitude. The samples with low concentrations of dopant cations exhibited good compositional stability and a reversible change in their structure parameters. At the same time, the solid solutions with a high concentration of lanthanum cations and/or copper cations (y, x ∼ 0.1) underwent partial decomposition.

Ceramic solid solutions (Bi 1 − x La x ) 4 V 2 O 11 − z (I), Bi 4 (V 1 − x Fe x ) 2 O 11 − y (II), and (Bi 1 − x La x ) 4 (V 0.96 Fe 0.04 ) 2 O 11 − y (III) ( x = 0–0.3, step Δ x = 0.02) are prepared using solid-phase synthesis. The concentration and temperature ranges of stabilization of different polymorphic modifications, including the ranges of concentrations x corresponding to the stabilization of the ferroelectric phase, are established. It is revealed that an increase in the concentration x in the region of existence of the pseudoorthorhombic phase α of the solid solutions studied leads to a decrease in the transition temperature, smearing of the transition, and an increase in the width of the thermal hysteresis of the ferroelectric phase transition. The effect of compressing of the domain walls by oxygen vacancies was revealed in the samples from the region of existence of the ferroelectric α phase, and the effect of dielectric relaxation was detected in the samples from the region of existence of the orthorhombic phase β.

Ceramic solid solutions Bi(4)(V(1-x)Cu(x))(2)O(11-y) with x = 0 divided by 0.2, Delta x = 0.02, have been prepared by the solid state reactions. The samples were studied by the DTA/DSC, X-ray diffraction and dielectric spectroscopy methods. Concentration and temperature stabilization regions of the polymorphous alpha, beta and gamma' modifications have been defined. Decreasing of the ferroelectric alpha-beta phase transition temperature, enlargement of the temperature interval of thermal hysteresis while increasing in temperature of the transition between tetragonal gamma'-gamma phases have been revealed. Dielectric measurements gave an indication on the effect of the domain walls "pinning" by oxygen vacancies inherent to the bismuth vanadate based compositions.

Ceramic solid solutions Bi-4(V1-xZrx)(2)O11-z (I), (Bi1-yLay)(4)V2O11-z (II) and (Bi1-yLay)(4)(V0.96Zr0.05)(2)O11-z (III) with x < 0.30, y < 0.20, were prepared by the solid state reaction method and were investigated by means of various experimental techniques. The low temperature ferroelectric alpha-phase exists in the solid solutions with x, y <= 0.05. The phase transition to paraelectric beta-phase was revealed in these compositions by the dielectric spectroscopy, SHG and DTA/DSC methods. Dielectric permittivity measurements confirmed an effect of the domain walls "pinning" due to the presence of oxygen vacancies inherent to the bismuth vanadate based structures. Switching of ferroelectric domains by an external electric field was observed in Piezo response Force Microscopy experiments.

Ceramic solid solutions Bi 4 (V 1 − x Me x ) 2 O 11 − y ( x = 0−0.3, Me = Zr, Ga, Fe) were obtained by solid-state synthesis. The homogeneity regions, x ≤ 0.3 for Me = Ga, Fe and x ≤ 0.15 for Me = Zr, were established. Structure parameters, microstructure, and the thermal, dielectric, and conducting properties of the samples were studied. The concentration and temperature ranges of the existence of different polymorphs and the concentration ranges x over which the high-conductivity phase was stable at ∼20°C were established. Using DTA, DSC, and dielectric spectroscopy, the α↔β and β↔γ phase transitions were revealed. It was found that the electrical conductivity of the solid solutions decreased as x increased.

The complex [(NH 2 ) 2 CSSC(NH 2 ) 2 ] 2 [OsBr 6 ]Br 2 · 3H 2 O is synthesized by the reaction of K 2 OsBr 6 with thiocarbamide in concentrated HBr and characterized using electronic absorption and IR absorption spectroscopy. Its crystal structure is determined by X-ray diffraction. The crystals are orthorhombic, a = 11.730(2) Å, b = 14.052(3) Å, c = 16.994(3) Å, space group Cmcm , and Z = 4. The [OsBr 6 ] 2− anionic complex has an octahedral structure. The Os-Br distances fall in the range 2.483–2.490 Å. The α,α′-dithiobisformamidinium cation is a product of the oxidation of thiocarbamide. The S-S and C-S distances are 2.016 and 1.784 Å, respectively. The H 2 O molecules, Br − ions, and NH 2 groups of the cation are linked by hydrogen bonds.

The polymorph phase stability ranges have been studied for the Bi4V2-xMexO11-y solid solutions with Me = Ga and Zr at room temperature. The formation of orthorhombic α- (x = 0.0 and 0.05) and β-phases (x = 0.1, 0.15) and tetragonal phase (0.2 ≤ x ≤ 0.3) has been revealed in BIGAVOX solid solutions. In BIZRVOX solid solutions, α-phase exists at x ≤ 0.05, while β-phase exists at 0.1 ≤ x ≤ 0.3. The second order phase transitions at ~ 308°C (BIGAVOX) and ~ 270°C (BIZRVOX) have been revealed for solid solutions with x = 0.05 using the SHG and DSC methods. In both systems, the β↔γ-phase transition temperatures have been found to decrease with increasing x.

The unit cell parameters in LnWO4Br compounds (Ln = La, Pr, Nd, Sm, Eu, Gd, Dy, Er, or Yb) are studied as functions of ionic radii in various systems. The best systems of ionic radii for the description of crystal-chemical laws in lanthanide oxobromotungstates are determined. Crystal-chemical plots are constructed for the unit cell parameters versus lanthanide ionic radius for the specified compounds, as well as the plot of the parameter c′ for the monoclinic crystal system that accounts for the monoclinic angle β.