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[Display omitted] The highly dispersed Bi–Ni–Sb–O pyrochlore was prepared under hydrothermal conditions with and without microwave treatment. Composite samples of NiO/(Bi–Ni–Sb–O pyrochlore) demonstrated consistently high activity without pretreatment in CO oxidation [ABSTRACT FROM AUTHOR]

[Display omitted] A series of layered solid solutions Y 2- x Fe 1+ x TaO 7 (x = 0–0.2) was synthesized and a structural transition (space group R 3 ¯ ↔ space group P 3 1 21) was observed at x = 0.1. In Y 2− x Fe 1+ x TaO 7 , which belongs to both structural types, geometrically frustrated 2D sublattices of kagome-type are formed, in which Fe3+ ions are coupled by short-range antiferromagnetic interactions, and the transition to the spin glass state is observed at T g ∼ 4.3 K. A phenomenon of weak ferromagnetism has been detected, the cause of which is probably a small tilt of the Fe3+ spins due to the Dzyaloshinskii–Moriya antisymmetric superexchange. [ABSTRACT FROM AUTHOR]

A series of solid solutions with compositions of La 1-x Tm x Ga 0.5 Sb 1.5 O 6 (x = 0.03, 0.05, 0.1) and La 1-x-y-z Tm x Tb y Dy z Ga 0.5 Sb 1.5 O 6 (x = 0.04, 0.07, 0.1; y = 0.04, 0.07, 0.1; z = 0.04, 0.04, 0.06) has been synthesized. It is shown that all the compounds have rosiaite structure (PbSb 2 O 6 , sp.gr. P-31m). Morphology, spectral-luminescent characteristics and color coordinates of the samples were studied. It was found that luminescence spectrum of thulium-activated samples recorded upon 351 nm excitation is typical for Tm3+ ions. At the same time, under excitation by radiation with λ = 457 nm and a power density of J = 4.7 kW/cm2, broadband thermal emission is observed, against which the bands corresponding to the 1G 4 →3H 6 , 1G 4 →3F 4 , 3F 4 →3H 6 и 3H 4 →3H 6 transitions of Tm3+ are detected. The luminescence spectra of the samples co-activated with Tm3+, Tb3+ and Dy3+are characterized by a relatively low intensity of the Tm3+ emission, which may be due to efficient energy transfer processes between Tb3+ and Dy3+ ions. A shift from the blue to the green color regions is observed in the color coordinates of the co-activated samples upon 351 nm excitation. Radiation with λ = 457 nm led to a shift in the emission colour to orange. Thus, it is shown that it is possible to create phosphors emitting in the blue, green and orange spectral regions by changing the wavelength of exciting radiation and activator composition for compounds with rosiaite structure. • La 1-x Tm x Ga 0.5 Sb 1.5 O 6 phosphorus exhibit blue emission under UV excitation. • nm intense excitation leads to thulium and broadband emission. • Co-doping by Tm3+, Tb3+ and Dy3+ shifts emission colour to green under UV excitation. • nm excitation of samples co-doped by Tm3+, Tb3+ and Dy3+ leads to orange emission. [ABSTRACT FROM AUTHOR]

New compounds with the rosiaite type structure LaM1/3Sb5/3O6, M = Co, Ni, and Cu, were synthesized. The compounds belong to quasi-two-dimensional magnets, in which magnetic interactions occur in the layers with a honeycomb structure. It is shown that there is no long-range magnetic order in these compounds. The temperature and field dependences of the magnetization in the compounds with M = Co, Ni indicate the presence of short-range anti-ferromagnetic and ferromagnetic exchange interactions. In the LaM1/3Sb5/3O6, M = Co, Ni, compounds, the interactions occur between Co2+ or Ni2+ ions of isolated magnetic clusters randomly distributed in the paramagnetic matrix in the chains of (M/Sb)O6 octahedrons. These clusters have sizes comparable with the crystal cell size. The LaCu1/3Sb5/3O6 compound is paramagnetic. [ABSTRACT FROM AUTHOR]

The impact of the synthesis method and morphology of the LaFe 0.5 Sb 1.5 O 6 samples on their catalytic activity in CO oxidation was studied in detail. The samples obtained by solid-phase reaction and co-precipitation showed higher catalytic activity. The features of the morphology, which cause the lowering of catalytic activity, were revealed for the samples synthesized in molten salts with and without preliminary microwave-hydrothermal treatment. A comparative study of all synthesized rosiaites LnFe 0.5 Sb 1.5 O 6 , Ln = La–Pr, LaFe 0.5-x Ga x Sb 1.5 O 6 and also pyrochlore Pr 2 (Fe,Sb)O 7 using an in situ diffuse reflection IR spectroscopy method was undertaken to clarify the mechanism of CO oxidation. It was revealed that in the course of the reaction the intermediate complexes of metal carbonyls are formed on the surface. At the same time, inactive carbonyls, which exist on the of Ce- and Pr-containing samples surface before the reaction mixture is fed, were found. This feature gives rise to a decrease in their catalytic activity. A reaction mechanism occurring via intermediate carbonyl complexes on the active centers - [Sb3+ - V O - - Fe3+] – is proposed. The CO oxidation on completely gallium-substituted samples indicates the existing of an additional channel for proceeding of redox process, which is not associated with Fe3+. It is suggested that the nature of this channel is possibly associated with a rosiaite layered structure, which creates a unique environment conducive to complex adsorption phenomena. [ABSTRACT FROM AUTHOR]

The layered oxide BiGeSbO 6 has been synthesized for the first time via solid state reaction. Rietveld refinement showed that BiGeSbO 6 belongs to PbSb 2 O 6 structural type (P-31m space group) with unit cell parameters a = 5.1314(9), c = 4.9974(1) Å, α = 90°, γ = 120°, Z = 1. Using the EXAFS and XANES methods, it was shown that a structural feature of this compound is a strong disordering of the Bi–O octahedron caused by the stereochemical activity of the 6s2 lone pair of Bi3+ electrons. A model according to which one oxygen vertex in the oxygen coordinated Bi3+ octahedron is absent, and the lone pair of electrons builds this polyhedron to the octahedron, was proposed. A particularity of the structure of BiGeSbO 6 is that the existing oxygen vacancy does not have a specific position. It was established that BiGeSbO 6 does not exhibit any polymorphic transition up until its incongruent melting point Т m = 985°С. Isobaric heat capacity was measured and thermodynamic functions (entropy, enthalpy increment and Gibbs free energy) were calculated for BiGeSbO 6 in the 10–1200 K temperature range. We found that the band gap of BiGeSbO 6 is due to the allowed direct interband transition with the energy of 3.16 eV. It was shown that BiGeSbO 6 has a wide transmission region in the visible and near-IR ranges. BiGeSbO 6 is a self-activated phosphor, but its luminescence spectrum is atypical for Bi3+-containing oxides. The luminescent properties of Bi 1-x Eu x GeSbO 6 solid solutions (x = 0.3, 0.5) were also studied. [ABSTRACT FROM AUTHOR]

We report on the first experimental evidence of the electrorheological effect in suspensions of superfine pyrochlore-type Bi 1.8 Fe 1.2 SbO 7 powders. Tensile-compressive and shear stress studies of the electrorheological fluids, with various filler contents, revealed an exceptionally high electrorheological effect in the materials – the tensile yield strength at 5 kV/mm reached about 20 kPa. The frequency dependencies of dielectric permittivity, dielectric loss tangent, and the conductivity of the suspensions with various filler contents allowed estimation of the dielectric permittivity values for superfine Bi 1.8 Fe 1.2 SbO 7 particles at zero and infinite frequencies. The study reveals new oxide materials as promising fillers for electrorheological fluids. Image 1 • Bi 1.8 Fe 1.2 SbO 7 powder was synthesized using a low-temperature approach. • Bi 1.8 Fe 1.2 SbO 7 suspensions in silicone oil demonstrated a high electrorheological effect. • Dielectric permittivity values for Bi 1.8 Fe 1.2 SbO 7 powders were estimated. [ABSTRACT FROM AUTHOR]

(Ln1.8Fe0.2)FeSbO7 (Ln = Pr–Tb) mixed oxides have been synthesized via coprecipitation followed by annealing. According to Rietveld refinement results, all of the oxides have the pyrochlore structure (sp. gr. Fd mz). The (Ln1.8Fe0.2)FeSbO7 compounds have been shown to exhibit high activity for CO oxidation reaction. The best results have been obtained for (Pr1.8Fe0.2)FeSbO7, which has a 90% CO conversion temperature T90 = 385°C. With increasing lanthanide atomic number, T90 rises monotonically from 385 to 550°C in going from Pr to Tb. This behavior is most likely due to the decrease of structural imperfection in the compounds with smaller lanthanide ionic radii. [ABSTRACT FROM AUTHOR]

The series of La 1-x Pr x Ga 0.5 Sb 1.5 O 6 solid solutions (x = 0–1) with PbSb 2 O 6 structure was synthesized. The comparative study of the La 1-x Pr x Ga 0.5 Sb 1.5 O 6 morphology showed all compounds have net microstructures. Herein the Pr concentration increasing leads to particles size decreasing from 400 up to 200 nm in the samples with low Pr content and to recrystallization and coarsening of the particles in Pr-rich ones. Using LaGa 0.5 Sb 1.5 O 6 as an example, it was shown that the compounds have a wide transmission region in the visible and IR spectral ranges and are characterized by a low-energy phonon spectrum. An analysis of the spectral-luminescent characteristics revealed the presence of a cross-relaxation process (1D 2 →1G 4) → (3H 4 →3F 4) of Pr3+ ions for La 1-x Pr x Ga 0.5 Sb 1.5 O 6 at x ≥ 0.07. It was showed that a broadband radiation of thermal nature is observed under laser excitation with λ = 457 nm and a power density of J = 4.65 kW/cm2 for the samples with high (x = 0.4–1) praseodymium content. • La 1-x Pr x Ga 0.5 Sb 1.5 O 6 solid solutions with PbSb 2 O 6 structure have been synthesized. • La 1-x Pr x Ga 0.5 Sb 1.5 O 6 have a wide transmission region in the visible and IR ranges. • The presence of a cross-relaxation process (1D 2.→1G 4)→(3H 4 →3F 4) of Pr3+ was shown. • The broadband radiation of thermal nature is observed. [ABSTRACT FROM AUTHOR]

Abstract—We have synthesized needle- and platelike α-Bi2O3 and Bi2O2CO3 nanoparticles. The bulk density of the α-Bi2O3 and Bi2O2CO3 powders is 8.5 and 6.9 g/cm3. The dielectric permittivity of α-Bi2O3 and Bi2O2CO3 has been calculated using dielectric permittivity and dielectric loss tangent dispersion measurements in the frequency range from 2.5 × 101 to 1 × 106 Hz for 40% suspensions (0.05 and 0.08 volume fractions of α-Bi2O3 and Bi2O2CO3, respectively) in PMS-300 polydimethylsiloxane. The value of ε∞ has been found to be 5.4 for α-Bi2O3 and 4.9 for Bi2O2CO3. Dielectric spectra of the suspensions have been shown to exhibit no relaxation behavior in the frequency range studied. We have compared the effects of the shape and dielectric permittivity of the particles on the magnitude of the electrorheological effect in them. Using a simple polarization model, we have analyzed the effect of the dielectric characteristics of the filler material on the yield stress τ0 of the suspensions in electric fields from 0 to 4 kV/mm. Using a combination of rheometric and direct microscopic observations, we have explained the effect of the type of filler on the electrorheological effect: the Bi2O2CO3-based ERFs have higher shear and compressive yield stresses, whereas the α-Bi2O3-based ERFs have a higher tensile yield stress. [ABSTRACT FROM AUTHOR]

Abstract The existence of the LnIIIFeIII 0.5 SbV 1.5 O 6 (Ln = La-Sm) series has been established for the first time. These compounds were prepared using the co-precipitation method with subsequent annealing. The systematic investigation, which includes phase equilibria study of the Ce 2 O x –Fe 2 O 3 –Sb 2 O y system, XRD, XANES, Rietveld refinement method and magnetic measurements has been carried out. It was shown that these ternary oxides are realized in PbSb 2 O 6 structure type (sp. g. P-31 m) and contain RE and Fe ions in +3 oxidation state. The comparative study of the morphology showed that the composition of the compounds do not affect the shape of the obtained quasi-spherical particles while the size decreases from 400 up to 100 nm in La Sm series. These antimonates exhibit high activity and stability in CO oxidation. The best result was obtained for LaFe 0.5 Sb 1.5 O 6 catalyst. The temperature of 90% CO conversion increases from 272 up to 426 °C in the series La > Ce > Pr > Nd > Sm. Highlights • New isostructural series of LnFe 0.5 Sb.5 O 6 (Ln = Ce-Sm) oxides has been synthesized. • LnFe 0.5 Sb.5 O 6 have layered trigonal lattice of PbSb 2 O 6 structure type. • LnFe 0.5 Sb 1.5 O 6 (Ln = La–Sm) demonstrate high activity in CO oxidation reaction. • The best result in the series was obtained for LaFe 0.5 Sb 1.5 O 6 catalyst. [ABSTRACT FROM AUTHOR]

The detailed study of magnetic properties, including dc and ac measurements, has been carried out on the Bi-Cr-Sb-O pyrochlore. The region of pyrochlore phase existence was determined and photocatalytic properties have been also studied. We revealed that the Bi-Cr-Sb-O pyrochlore phase occurs along Bi 2−x Cr 1+x SbO 7 section within the region x = 0.1–0.4. The Cr 3+ ions oxidation state in Bi-Cr-Sb-O pyrochlore was confirmed by XANES spectra. The best Rietveld refinement results for Bi 1.8 Cr 1.2 SbO 7 composition were achieved for the disordered structure model (space group Fd-3m ). According to the magnetic data Bi 1.8 Cr 1.2 SbO 7 is a highly frustrated pyrochlore with short-range antiferromagnetic exchange interactions between the nearest Cr 3+ ions. At T g  = 4 К this compound undergoes spin-glass transition. [ABSTRACT FROM AUTHOR]

The region of pyrochlore existence in the Bi-Mn-Sb-O system, Mn valence state and magnetic properties of pyrochlore compounds have been studied. It is shown that a pyrochlore phase exists in the vide range х = 0.2–0.8 along the Bi (2−x) Mn (1+x/2) Sb (1+x/2) O 7 section. Rietveld structure refinement, XANES and EXAFS data show that Bi-Mn-Sb-O pyrochlores are structurally disordered and manganese is in Mn 2+ /Mn 3+ mixed-valence state. Mn 2+ ions occupy a part of eight coordinated Bi sites while Mn 3+ ions are in strongly distorted octahedra. Magnetic measurements confirm the structural data and reveal strong dependence of magnetic properties on Mn concentration. According to dc and ac susceptibility data all studied pyrochlores demonstrate a transition to the conventional spin glass state at T f ≤ 7 K. The transition temperature decreases with the decrease of Mn 3+ amount in the pyrochlore octahedral sublattice. It was also revealed that there exists a threshold Mn concentration above which we detected an antiferromagnetic transition at T N = 42 K along with an SG transition. [ABSTRACT FROM AUTHOR]

A technique has been developed for fluorinating the pyrochlore oxide BiFeFeSbO, and a compound with the composition BiFeSbOF has been obtained. The synthesized oxyfluoride also has the pyrochlore structure (sp. gr. Fd3 m), with a lattice parameter a = 10.4443(1) Å ( R = 5.2). It has been shown that the charge balance upon fluorine substitution for oxygen is maintained not through partial reduction of Fe to Fe but through the incorporation of fluorine into oxygen vacancies. The magnetic behavior of the fluorinated pyrochlore phase is determined by the persisting frustration of the octahedral sublattice, which is responsible for the development of a spin glass state below T = 12 K. The fluorination-induced changes in the anion sublattice led to an increase in the antiferromagnetic exchange interaction between neighboring Fe ions and changes in the dynamic properties of the spin glass phase. [ABSTRACT FROM AUTHOR]

A series of Bi 1.8 Fe 1.2(1−x) M 1.2x SbO 7 (M = Ga, Al) compositions with substitution of Fe 3+ for diamagnetic Ga 3+ and Al 3+ has been synthesized and characterized by XRD, Mössbauer spectroscopy and magnetic measurements. X-ray diffraction analysis indicate that the Bi 1.8 Fe 1.2(1−x) Ga 1.2x SbO 7 (x = 0–1) at the whole x range and Bi 1.8 Fe 0.84 Al 0.36 SbO 7 (x = 0.3) are solid solutions of pyrochlore structure. With an increase of Ga 3+ content the substitution of Fe 3+ for Ga 3+ occurs disproportionally over A- and B-sites while Al 3+ ion incorporates entirely on B-site. Magnetic measurements showed that all studied compositions fall into the category of disordered, magnetically frustrated materials and at T ≤ 13 K undergo spin-glass transition. The spin-glass phases have a striking sensitivity to substitution of Fe 3+ for Ga 3+ or Al 3+ . The comparison of the magnetic behavior of Ga- and Al-containing pyrochlores revealed that, most likely, freezing temperature is governed by Fe 3+ ions residing especially on octahedral B-sites. [ABSTRACT FROM AUTHOR]

The Bi-La-Fe-Sb-O, Pr-Fe-Sb-O, and Bi-Pr-Fe-Sb-O systems have been shown to contain pyrochlore solid solutions. We have determined the limits of the PrFeSbO and BiLnFeSbO (Ln = La, Pr) solid solutions and shown that there is no compound corresponding to the 'ideal' composition PrFeSbO. Analysis of the magnetic properties of the synthesized compounds indicates that rare earth substitution for bismuth ions has no effect on the spin glass transition and that the spin glass state is only determined by the interaction between the Fe spins on the octahedral site. The Pr paramagnetic ion in PrFeSbO does not participate in the formation of the spin glass state but makes a paramagnetic contribution to the total magnetic susceptibility, which is especially significant at low temperatures. [ABSTRACT FROM AUTHOR]

Phase equilibria in the La 2 O 3 -Fe 2 O 3 –Sb 2 O 5 system have been studied. The isothermal section was constructed at T=900 °С. The existence of the ternary oxide LaFe 0.5 Sb 1.5 O 6 was confirmed. The structure of this compound was solved using Rietveld refinement of synchrotron radiation-based powder XRD data. LaFe 0.5 Sb 1.5 O 6 crystallizes in a trigonal layered structure relating to PbSb 2 O 6 type (space group P-31m, a=b=5.2446(3) Å, c=5.1930(3) Å, Z=1). The fine powder of LaFe 0.5 Sb 1.5 O 6 was prepared by molten salt synthesis. The compound was characterized by diffuse reflection and Mossbauer spectroscopy, magnetic measurements, scanning electron microscopy and photocatalytic tests. The magnetic behavior of LaFe 0.5 Sb 1.5 O 6 in the applied magnetic field H=5000 Oe is entirely paramagnetic. By contrast, in the small magnetic field H=100 Oe the magnetic data of LaFe 0.5 Sb 1.5 O 6 indicates an unusual critical behavior near phase transition at T<2 K. [ABSTRACT FROM AUTHOR]

A method has been developed for the preparation of Bi-Fe-Sb-O pyrochlore nanoparticles by microwave hydrothermal treatment. Experiments revealed that the preparation procedure for the precursors is an important factor that affects the phase composition of the product. The morphology of the pyrochlore particles was investigated by SEM, HRTEM, and selected-area electron diffraction (SAED) methods. The samples consist of numerous spherical agglomerates from 100 to 200 nm formed from 20 nm mutually oriented nanocrystallites. A mechanism for the formation of the particles is proposed, and the magnetic and photocatalytic properties of the Bi-Fe-Sb-O pyrochlore nanocrystallites are reported. [ABSTRACT FROM AUTHOR]

In this paper, we report the first Bi4Ge3O12-based thin-layer alpha radiation detector. The scintillator was immobilized on a fused silica substrate via pulsed laser irradiation of BGO powder consisting of submicron particles. Laser treatment conditions were shown to influence the morphology and kinetic characteristics of the scintillator. The material we prepared ensures a higher stability of detectors to moisture and air in comparison with its commercially available analogs, while offering a comparable or even higher detection efficiency, and can be used in environmental monitoring, including volumetric alpha activity measurements. [ABSTRACT FROM AUTHOR]

Phase equilibria in the Bi 2 O 3 –NiO–Sb 2 O 5 system have been investigated. The isothermal section of the system (650°) has been constructed. For the first time the existence of the pyrochlore structure solid solution, (Bi 2− x Ni x )Ni 2/3− y Sb 4/3+ y O 7± δ , x =0.1−0.35, y =0−0.1, and a new compound Bi 3 Ni 2/3 Sb 7/3 O 11 of KSbO 3 structure type have been discovered. The structures and properties of these compounds were studied by XRD, XAFS, diffuse reflection spectroscopy and magnetic methods. Rietveld refinement of synchrotron radiation-based powder XRD data for pyrochlore sample of 38.43Bi 2 O 3 –33.0NiO–28.57Sb 2 O 5 composition and Bi 3 Ni 2/3 Sb 7/3 O 11 compound was performed. The best possible refinement of the positional parameters for both pyrochlore and Bi 3 Ni 2/3 Sb 7/3 O 11 structures was achieved for disordered models. Magnetic, diffuse reflection and an X-ray absorption spectroscopy study confirmed that in both compounds nickel ions are mainly in a 2+ oxidation state. According to magnetic data, Bi 1.84 Ni 0.16 (Ni 0.63 Sb 1.37 )O 7 pyrochlore and Bi 3 Ni 2/3 Sb 7/3 O 11 are overall paramagnetic in nature. [ABSTRACT FROM AUTHOR]

The refinement of the Bi 2 O 3 –Fe 2 O 3 –Sb 2 O 5 system phase diagram has been performed and the existence of the two ternary compounds has been confirmed. The first one with a pyrochlore-type structure (sp. gr. Fd 3̄ m ) exists in the wide solid solution region, (Bi 2− x Fe x )Fe 1+ y Sb 1− y O 7± δ , where x =0.1–0.4 and y =−0.13–0.11. The second one, Bi 3 FeSb 2 O 11 , corresponds to the cubic KSbO 3 -type structure (sp. gr. Pn 3̄) with unit cell parameter a =9.51521(2) Å. The Rietveld structure refinement showed that this compound is characterized by disordered structure. The Bi 3 FeSb 2 O 11 factor group analysis has been carried out and a Raman spectrum has been investigated. According to magnetization measurements performed at the temperature range 2–300 K it may be concluded that the Bi 3 FeSb 2 O 11 magnetic properties can be substantially described as a superposition of strong short-range antiferromagnetic exchange interactions realizing inside the [(FeSb 2 )O 9 ] 3D-framework via different pathways. [ABSTRACT FROM AUTHOR]

A new composite material consisting of BiFeO 3 crystallites inside a nonmagnetic glass-like matrix has been synthesized using the glass crystallization method. The phase equilibrium and glass formation region of the Bi 2 O 3 –Fe 2 O 3 –B 2 O 3 system (0–50 mol % B 2 O 3 ) have been investigated. The optimal compositions for glass–ceramic synthesis are within the 25–85 mol % BiFeO 3 range on the Bi 4 B 2 O 9 –BiFeO 3 section. The obtained ceramics were studied by X-ray diffraction, Raman spectroscopy, microscopic and magnetic methods. It was shown that the BiFeO 3 crystallites grow according to a dendrite mechanism resulting in anisotropic glass–ceramic. Magnetic properties of the synthesized samples depend upon their morphology and crystallinity. [ABSTRACT FROM AUTHOR]

60BO-32CaF-8BiO glasses codoped with chromium and neodymium have been prepared for the first time, and their luminescence properties have been studied. The glasses have been shown to contain chromium in two oxidation states. We have obtained luminescence spectra of Cr in octahedral coordination and Cr in tetrahedral coordination. Energy transfer from Bi to Nd and Cr has been demonstrated. [ABSTRACT FROM AUTHOR]

Highlights: [•] We have constructed the isothermal section of the system Bi2O3–Fe2O3–Sb2O x . [•] Ternary compound formation is limited to pyrochlore, which forms a solid solution region. [•] The phase diagram points out that 7–25% of Bi-positions are occupied with Fe3+. [•] The Mossbauer data confirmed that Fe3+ ions enter the Bi-positions. [•] Magnetic measurements revealed spin-glass magnetic transition at 9K. [ABSTRACT FROM AUTHOR]

The glass-forming region in the CaF-BiO-BO system has been determined for the first time. We have prepared glasses of various compositions, investigated their physicochemical properties, and examined the effect of rare-earth (La, Nd, Eu, Dy, Er, Tm, Yb) doping on the crystallization behavior of the glasses. Transparent glass-ceramics containing ∼40-nm CaEuF and CaLaF crystallites have been obtained. The luminescence properties of the glasses and glass-ceramics have been studied. [ABSTRACT FROM AUTHOR]

We have studied the effect of mechanochemical activation on the reactivity of BiO + FeO oxide mixtures, assessed the temperature effect on the kinetics of BiFeO formation in the oxide mixtures before and after mechanochemical activation, and optimized the conditions of bismuth ferrite synthesis by solid-state reaction. A material with a BiFeO content of at least 98.3 wt % has been obtained, and its magnetic properties have been investigated. [ABSTRACT FROM AUTHOR]

The kinetics of BiFeO formation from xerogel prepared by reverse coprecipitation were studied at different synthesis temperatures. We examined the influence of annealing temperature on the morphology of the reaction products and optimized synthesis conditions, which allowed us to obtain 99.7 wt % pure BiFeO consisting of crystalline grains less than 50 nm in size. Its magnetic properties were investigated. [ABSTRACT FROM AUTHOR]

We gave studied the crystallization behavior of 30BaO · 25BiO · 45BO glasses doped with EuO to different levels. At a EuO content of 7 mol % or higher, the glasses undergo volume crystallization. The only precipitating phase is a solid solution between europium and bismuth oxides. With increasing europium concentration in the glass, the structure of the crystallites changes from cubic to rhombohedral. We have investigated the morphology, physicochemical properties, and luminescence spectra of the glasses and glass-ceramics. [ABSTRACT FROM AUTHOR]

We have prepared europium-doped BaO-Bi2O-B2O glasses and investigated the doping effect on the main physicochemical properties and local structure of the glasses. Using Judd-Ofelt analysis, we calculated intensity parameters (Ω, Ω, and Ω), spontaneous emission probabilities, the radiative lifetime, luminescence branching factors, the quantum yield of luminescence, and the stimulated emission cross sections for D → F transitions. [ABSTRACT FROM AUTHOR]

Single-crystalline species of the novel compounds BaBiBO and CaBiBO with Pna2 structure were successfully grown by the top-seed solution growth (TSSG) method and solid-state recrystallization, respectively. X-ray diffraction methods were used to confirm the symmetry of the crystal structure and to determine unit cell parameters. Normal-mode classification and assignment were performed from the results of polarized Raman and IR absorption measurements on the obtained crystals. The high-frequency part of the vibrational spectra of both materials (580-1400 cm) is reminiscent of the normal modes of the isolated [BO] group. The expected crystal-field induced changes in these modes from group-theoretical considerations provide important clues for the normal-mode assignment of the high-frequency spectral lines. [ABSTRACT FROM AUTHOR]

This work examines the effect of KBF4 additions on the crystallization behavior of glasses based on the multicomponent systems MO-Bi2O3-B2O3 with M = Ca, Sr, and Ba. The glass-ceramic composites obtained contain a δ-Bi2O3-based crystalline phase with a crystallite size of ≃7 nm, evenly distributed over the glass matrix. The 400°C electrical conductivity of the nanocomposites reaches 2 × 10−4 S/cm, and the activation energy is 1.1 eV, typical of anion conduction. These values are comparable to those reported for δ-Bi2O3 ceramics. [ABSTRACT FROM AUTHOR]

This review is devoted to a new nonlinear optical material BiB3O6 (BIBO). It systemizes data on the phase equilibrium, structure, polymorphism, and growth characteristics of single crystals of this compound and considers its main properties and fields of application. The bibliography includes 122 references. [ABSTRACT FROM AUTHOR]

It is shown using Bi12TiO20 as an example that doping of a sillenite phase leads to the formation of a solid solution between it and the Bi12M xO20 ± δ phase corresponding to the dopant. This gives rise to structural features characteristic of the second phase and, accordingly, results in the formation of the corresponding optical centers. Dopant atoms occupy tetrahedral (M) sites. In addition, in the case of heterovalent substitutions the M site is partially occupied by the Bi atoms of [BiO3] groups. The structural features of sillenites are governed by the oxidation state of the M cation. Accordingly, doping with ions in the same oxidation state leads to the formation of similar optical centers and, as a consequence, produces similar changes in the properties of the material. The results obtained are supported by experimental studies of the absorption, circular dichroism, photoinduced absorption, and photoconductivity spectra of doped sillenite crystals in a wide spectral range. [ABSTRACT FROM AUTHOR]

• Novel Eu/Tb/Dy-contained phosphors with rosiaite-type structure were synthesized. • Particle size for the Bi 1−x Ln x GeSbO 6 is higher than for the La 1−x Ln x Ga 0.5 Sb 1.5 O 6. • Bi 1−x Ln x GeSbO 6 and La 1−x Ln x Ga 0.5 Sb 1.5 O 6 exhibited different luminescent properties. • Addition of Tb3+/Dy3+ to Eu3+ changed the emission from red-orange to yellow-orange. In this work, novel phosphors LaGa 0.5 Sb 1.5 O 6 and BiGeSbO 6 doped with Eu3+, Tb3+, and Dy3+ were synthesized, and the luminescent properties were studied. The impact of the host type on the emission properties was demonstrated for compositions singly doped with Eu3+ and Dy3+ ions. For the La 1−x Eu x Ga 0.5 Sb 1.5 O 6 and Bi 1−x Eu x GeSbO 6 (x = 0.05–0.5) solid solutions, there were evident differences in the luminescence intensity ratio of the bands caused by the 5D 0 →7F 1 and 5D 0 →7F 2 transitions of Eu3+ that may have resulted from a different rare earth (RE) ion coordination environment. The spectra of all the bismuth-containing solid solutions were characterized by the appearance of an additional band related to the intrinsic luminescence of the bismuth-containing host. The intensity ratio of this band and the RE ion emission lines for dysprosium-containing compounds was much higher than that for compositions doped with praseodymium and europium. Co-doping with Eu3+, Dy3+, and Tb3+ ions led to a shift in the emission colour to orange (when doped with two types of RE ions) and yellow-orange (when doped with three types of RE ions). [ABSTRACT FROM AUTHOR]

• Thermodynamic properties for RE 2 FeTaO 7 , RE = Sm, Gd, were studied at 5–1300 K. • The magnetization measurements at 2.3–300 K were carried out for Y 2 FeTaO 7 and Sm 2 FeTaO 7. • Abnormal heat capacity contribution at T < 25 K is due to magnetic properties of RE 2 FeTaO 7. The isobaric heat capacity of pyrochlore-related compounds RE 2 FeTaO 7 (RE = Sm and Gd) was measured using an adiabatic and a differential scanning calorimetry over a wide temperature range using adiabatic and differential scanning calorimetry. An anomaly on the curves of all the compounds is clearly observed within the low-temperature range, T < 25 K, while at the high temperatures the peculiarities were not detected. The standard thermodynamic functions: heat capacity, entropy, enthalpy change and reduced Gibbs energy of studied RE 2 FeTaO 7 were calculated. The entropy of the anomalous contribution was equal to (14.8 and 19.6) J⋅K−1⋅mol−1 for Sm 2 FeTaO 7 and Gd 2 FeTaO 7 , respectively. A comparative study of Y 2 FeTaO 7 and Sm 2 FeTaO 7 confirmed the relationship of low temperature magnetic properties with a heat capacity anomaly. The DC and AC magnetization measurements within the (300–2.3) K temperature range and in magnetic fields up to 5 kOe revealed spin glass (SG) transitions for Y 2 FeTaO 7 and Sm 2 FeTaO 7 at 4 K and 9 K, respectively. Against the background of developing SG in the frustrated Kagome sublattice, an antiferromagnetic transition at T ~ 8 K was detected for Sm 2 FeTaO 7 in a large magnetic field. This transition occurs in Sm-sublattice and is responsible for the large magnetic contribution to the anomalous low temperature heat capacity in Sm 2 FeTaO 7. [ABSTRACT FROM AUTHOR]

The physicochemical properties of BaO-Bi2O3-B2O3 glasses have been studied. The effect of KBF4 additions on the properties of the glasses has been examined. The transmission of the glasses has been correlated with their local structure and composition. [ABSTRACT FROM AUTHOR]

The 600°C (subsolidus) section of the CaO-Bi2O3-B2O3 phase diagram has been studied by x-ray diffraction and differential thermal analysis. A new calcium bismuth borate of composition CaBi2B4O10 has been identified, and the existence of CaBi2B2O7 has been confirmed. According to T-x phase diagram data, these compounds form peritectically at 700±5 and 783±5°C, respectively. [ABSTRACT FROM AUTHOR]

The axial circular-dichroism spectrum of a synthetic amethyst crystal has been studied for the first time. Bands both of the positive and negative signs are revealed. New information on the color centers of amethyst and their electronic structure is obtained. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The vibrational spectra of crystals of bismuth borates Bi24B2O39 ,Bi4B2O9 ,BiBO3 , and Bi2B8O15 were obtained for the first time, and the spectra of Bi3B5O12 and BiB3O6 crystals measured in the range 30–1600cm–1 at room temperature were refined. The lines observed were assigned to the corresponding vibrational transitions on the basis of the theoretical group analysis and comparison of the obtained results with the vibrational spectra of borates of different composition. The complication of the structure of bismuth borates with increasing content of B2O3 was traced by the example of vibrational spectra. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Absorption and circular-dichroism spectra of iron-doped AlPO[sub 4] crystals have been studied. For the first time, the experimental data on the electronic states of the [FeO[sub 4]][sup 5-] complex are obtained in the range from 190 to 350 nm with due regard for the interactions that cannot be described within the one-electron approximation. The bands observed in the absorption and circular-dichroism spectra are attributed to corresponding electronic transitions. The advantages of the use of crystal-field-induced circular dichroism in comparison with other spectroscopic methods in the analysis of the electronic states of impurity ions in gyrotropic crystalline matrices are considered on the [FeO[sub 4]][sup 5-] complex. [ABSTRACT FROM AUTHOR]

The Raman spectra of Bi[sub 24]A1PO[sub 40] and Bi[sub 38]ZnO[sub 58] crystals have been studied for the first time. The polarization Raman spectra of Bi[sub l2]GeO[sub 20], Bi[sub 12]TiO[sub 20], Bi[sub 24]A1PO[sub 40], and Bi[sub 38]ZnO[sub 58] crystals are also studied. The lines in the Raman spectra ofBi[sub 12]TiO[sub 20], Bi[sub 24]A1PO[sub 40], and Bi[sub 38]ZnO[sub 58] are identified and compared with the lines of the Bi[sub 12]GeO[sub 20] spectra studied earlier. It is shown that the differences in the Raman spectra of the crystals studied are associated with the specific features of their atomic structures. [ABSTRACT FROM AUTHOR]

The experimental data on the optical and chiro-optical properties of crystals with the sillenite structure Bi[sub 12]M[sub x]O[sub 20 ± δ] (M = elements of II-VIII groups) have been reviewed. The relations between the changes in the chemical composition, the crystal structure of Bi[sub 12]M[sub x]O[sub 20 ± δ] compounds, absorption, circular dichroism, and optical rotation spectra of sillenites have been established. A model taking into account the contribution of the electronic transitions of optically active tetrahedral [MO[sub 4]][sup n-] complexes to the total optical rotation in sillenites is suggested. The data on the state (oxidation degree) and the recharging processes of 3d-elements in sillenites are systematized. The models of optical centers responsible for the photochromic effect in sillenites are critically analyzed. [ABSTRACT FROM AUTHOR]

In this work, Bi 1-x Pr x GeSbO 6 (x = 0–0.5) solid solutions were synthesized, and the corresponding properties were compared to those of La 1-x Pr x Ga 0.5 Sb 1·5 O 6. The lattice parameters of the La 1-x Pr x Ga 0.5 Sb 1·5 O 6 solid solutions decrease linearly as the activator concentration increases. This linear reduction is only observed for the a parameter for Bi 1-x Pr x GeSbO 6. Parameter c shows non-linear growth, which is related to the structural features of BiGeSbO 6. Increasing the activator content leads to a decrease in the particle size, which is 0.5–8 μm for Bi 1-x Pr x GeSbO 6. The influence of the host composition on the spectral-luminescent properties of the solid solutions was determined. The difference in the phonon frequencies of BiGeSbO 6 and LaGa 0.5 Sb 1·5 O 6 leads to different luminescence quenching processes for Pr3+ ions. Interactions between Pr3+ ions and Bi3+ were observed for Bi 1-x Pr x GeSbO 6 solid solutions. These processes give rise to changes in the ratios of the luminescence bands of these ions. All the bismuth-containing solid solutions are characterized by the appearance of an additional band in the spectrum related to the luminescence of the bismuth centres of the BiGeSbO 6 host. An evaluation of the colour coordinates (CIE 1931) of the Bi 1-x Pr x GeSbO 6 luminescence showed that the colour of the radiation depends on the praseodymium content: as the praseodymium content increases, the luminescence changes from orange (x = 0.005, 0.01) to yellow-green (x = 0.05–0.5). Broadband thermal emission is observed for Bi 0.5 Pr 0.5 GeSbO 6 under laser excitation with λ = 457 nm and a power density of J = 6 kW/cm2. • Bi 1-x Pr x GeSbO 6 solid solutions with a PbSb 2 O 6 structure were synthesized. • Bi 1-x Pr x GeSbO 6 solid solutions exhibited different Pr3+ luminescence from that of La 1-x Pr x Ga 0.5 Sb 1·5 O 6. • Interactions between Pr3+ ions and Bi3+ were observed. • The luminescence changed from orange to yellow-green as x increased. • Broadband thermal emission was observed for Bi 0.5 Pr 0.5 GeSbO 6. [ABSTRACT FROM AUTHOR]

• New ferromagnetic Ln 2 CrTaO 7 (Ln = Y, Sm, Gd) pyrochlores are synthesized. • Ferromagnetism is caused by FM interactions in the chromium sublattice. • In Y 2 CrTaO 7 a negative coefficient of thermal expansion is detected at T ≤ 140 K. • In (Sm, Gd) CrTaO 7 a competition of AFM and FM magnetic interactions is observed. • Four FM transitions and RSG are detected in Gd 2 CrTaO 7 at low temperatures. New complex Cr-containing pyrochlores Ln 2 CrTaO 7 , Ln = Y, Sm, Gd, were synthesized. The Rietveld refinement of the Ln 2 CrTaO 7 composition confirmed the pyrochlore type of the structure. The Cr3+ oxidation state is corroborated by XANES spectra. The detailed study of DC and AC magnetization of Ln 2 CrTaO 7 , Ln = Y, Sm, Gd, was carried out in the temperature range 2–300 K and magnetic field up to 5 T. FM phase transitions at 143, 192, and 163 K were observed in pyrochlores with Y, Sm, and Gd, respectively. It is shown that these transitions are due to canted antiferromagnetism or weak-ferromagnetism in the Ln 2 CrTaO 7 pyrochlores. AFM interactions between Ln- and Cr-sublattices in Sm 2 CrTaO 7 and Gd 2 CrTaO 7 causes AFM transition at T = 42 K, after which magnetization continues increasing. Unusual magnetic properties were observed for Gd 2 CrTaO 7 at low temperatures. Competitive FM and AFM interactions in Cr-and Gd-sublattice give rise to the occurrence of reentrant spin glass at T < 20 K. FM transition at 11 K is also detected. Spin glass state exists along with strong FM interactions. The effect of the magnetic properties on thermal expansion is also investigated for these compounds. [ABSTRACT FROM AUTHOR]

Abstract: Bi12SiO20 crystals doped with Cu were grown by the Czochralski method along from a melt. The concentration of the impurities was determined by electro–thermal and flame atomic absorption spectroscopy. The lattice parameter was determined by single-crystal diffractometry. Results from Raman measurements in different scattering configurations lead to the conclusion that distinguishable structural distortions of the bismuth–oxygen framework of the sillenite lattice take place due to Cu doping. [Copyright &y& Elsevier]

A procedure for the synthesis of the LaCo1/3Sb5/3O6 layered oxide with a rosiaite structure has been developed. The method is based on the hydrothermal treatment of coprecipitated sediments with their subsequent annealing. The resulting material has proven to be an efficient catalyst in the CO oxidation reaction. This result confirms the prospects of using compounds with the rosiaite structure in oxidative catalysis reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] The existence of Y 2 – x Ca x FeTaO 7- δ solid solutions (x = = 0 – 0.075) with a pyrochlore-like layered structure was established. The appearance of the magnetic properties characteristic for canted antiferromagnets was observed as a result of structure distortions (space group R 3 ¯ ® space group P 3 1 21) associated with a change of composition. Y 2 – x Ca x FeTaO 7 – δ exhibits ferromagnetic properties already at 300 K. [ABSTRACT FROM AUTHOR]

The pyrochlore-type solid solution (Bi2-xNix) Ni2/3-ySb4/3+yO7+-δ (x = 0.1-0.35, y = 0-0.1) and Bi3Ni2/3Sb7/3O11 of the KSbO3 structure type are discovered in the 650 °C isothermal section of the Bi2O3-NiO-Sb2O5 phase diagram. [ABSTRACT FROM AUTHOR]

A process for the growth of VSe and VTe single crystals using VCl as a transport agent is proposed and experimentally demonstrated. X-ray diffractometry and Laue X-ray photography results indicate that the crystals thus grown are identical in properties to chalcogenide crystals grown using I as a transport agent. The mechanism of chemical vapor transport is discussed and the process conditions are optimized. [ABSTRACT FROM AUTHOR]