One-pot sequential synthesis of magnetically separable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/AgCl photocatalysts with enhanced activity and stability

Magnetically separable Fe₃O₄/AgCl photocatalysts were prepared by a one-pot sequential method. A series of techniques proved the hybrid structure of Fe₃O₄/AgCl composites. Fe₃O₄/AgCl composites had a much higher photocatalytic activity toward Rhodamine B (RhB) degradation than pure AgCl under the simulated solar light irradiation. The existence of metal Ag resulted in high photocatalytic activity of Fe₃O₄/AgCl, which was related with the amount of metallic Ag. The scavenging experiments showed that the degradation reaction most probably was initiated by the photoinduced single-electron transfer, and the generation of superoxide anion (O ₂ ^-· ) played a significant role. The composite photocatalysts could be recycled by applying an external magnetic field, and the reused composites maintained their original photocatalytic activity. Fe₃O₄/AgCl composites were highly efficient, magnetically separable, and recoverable. This proves their potential applications in the photodegradation of organic pollutants.     

Synthesis and characterization of polyaniline–zirconium dioxide and polyaniline–cerium dioxide composites with enhanced photocatalytic degradation of rhodamine B dye

For the first time, chloroform and 2-butanol were used as solvent systems for the preparation of ZrO₂–PANI and CeO₂–PANI composites. Solubility of the synthesized composites was studied in chloroform, N-methyl-2-pyrrolidinone (NMP), and in mixture of toluene?+?2-propanol (2:1). XRD and cyclic voltammetry data showed that the ZrO₂–PANI and CeO₂–PANI composites possess both crystalline and amorphous domains indicating some sort of conductivity. TGA results showed that ZrO₂–PANI composite have a better thermal stability than pure PANI; however, CeO₂–PANI composite has lower thermal stability than pure PANI. The conjugated unsaturated structure of PANI is responsible for the enhanced photocatalytic properties of ZrO₂–PANI and CeO₂–PANI. Photocatalytic results showed that, at photolysis time of 60 min, rhodamine B (RhB) dye was degraded up to 34 and 35% by ZrO₂–PANI and CeO₂–PANI, respectively. The degradation products of RhB were quantified by LC–MS and GC–MS, and accordingly, a detailed pathway was proposed.     

Preparation of mesoporous Ce<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> mixed oxides and their catalytic properties in methane combustion

Mesoporous Ce_{1 ? x} Fe _x O₂ mixed oxide catalysts of different molar ratios (x = 0.1–0.5) were prepared by the citric acid sol-gel method and the microwave technique. The activities of Ce_{1 ? x} Fe _x O₂ mixed oxides on methane combustion were investigated, and the structure and reductive properties were characterized by XRD, BET, DRS, and TPR. The data showed that Ce_{1 ? x} Fe _x O₂ mixed oxides prepared were mesoporous material. When x ≤ 0.2, the transition metal Fe incorporated into the lattice of CeO₂ to form cubic Ce_{1 ? x} Fe _x O₂ solid solutions, and mixed phases of cubic Ce_{1 ? x} Fe _x O₂ solid solutions and α-Fe₂O₃ existed when x > 0.2. Ce_{1 ? x} Fe _x O₂ solid solutions show higher activity for methane combustion than pure CeO₂, especially for Ce_0.9Fe_0.1O₂.     

Saw-sedge <Emphasis Type="Italic">Cladium mariscus</Emphasis> as a functional low-cost adsorbent for effective removal of 2,4-dichlorophenoxyacetic acid from aqueous systems

For the first time in the published literature, a study is described concerning the use of the saw-sedge Cladium mariscus (C. mariscus) for adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous systems. Among the experiments carried out, the elemental composition of C. mariscus was determined (C = 48.0 %, H = 7.1 %, N = 0.95 %, S = 0.4 %), FTIR spectroscopic analysis was performed to confirm the chemical structure of the adsorbent, and porous structure parameters were measured: BET surface area (A _BET  = 0.6 m²/g), total pore volume (V _p  = 0.001 cm³/g) and average pore size (S _p  = 6.6 nm). It was shown that the effectiveness of removal of 2,4-D from aqueous systems using C. mariscus depends on parameters of the process: contact time, system pH, mass of sorbent, and temperature. Maximum adsorption was attained for a solution at pH = 3. Further increase in the alkalinity of the tested systems led to a reduction in the effectiveness of the process. The kinetic of adsorption of 2,4-D by C. mariscus was also determined, and thermodynamic aspects were investigated. The experimental data obtained correspond to a pseudo-second-order kinetic model of type 1. Additionally the negative values obtained for ΔHº indicate that the process is exothermic, and the negative values of ΔGº show it to be spontaneous. As the temperature of the system increases the spontaneity of adsorption is reduced, in accordance with the exothermic nature of the process.     

Synthesis of monodisperse pancake-like Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript> with prominent photocatalytic performances

Uniform Bi₂WO₆ pancakes were prepared via a solvothermal route in a solvent mixture of glycerol (Gly) and water (V/V = 1). A variety of techniques including scanning electron microscopy, transmission electron micrographs, X-ray powder diffraction, Brunauer–Emmett–Teller, FT-IR spectra, and UV–Vis diffuse reflectance spectra, were employed to characterize the structure and properties of the as-obtained Bi₂WO₆. It was found that Bi₂WO₆ pancakes showed prominent photocatalytic performance for the degradation of rhodamine B (RhB) under visible light (λ ≥ 420 nm) irradiation, which can be attributed to its good crystallization, large surface area, unique morphology and structural features.     

Electrodeposition of Fe<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript>Se<Subscript> <Emphasis Type="Italic">y</Emphasis> </Subscript> films from acidic solutions

Iron selenide (Fe_xSe_y) thin films were electrodeposited on a glassy carbon electrode (GCE) surface under constant potential and pulse potential modes. The deposition mechanism was investigated using cyclic voltammetry. Electrochemical processes at room temperature are accompanied by adsorption of selenium on the electrode surface and complicated by chemical reactions in the solution bulk. Several approaches to control the film stoichiometry were applied: varying of electrodeposition potential; the use of elevated temperatures (60–80°C) to decrease the electrode passivation and electrodissolution of interfering elements under pulse mode. The composition of Fe_xSe_y thin films was analyzed using an energy dispersive X-rays (EDX) analysis.     

Cluster-associated filling of water molecules in graphene-based mesopores

Graphene monoliths were prepared through unidirectional freeze-drying method of graphene oxide colloids-KOH mixed solution and successive reduction by heating at 573 K in Ar. The porosity- and crystallinity-controlled graphene monoliths were prepared by the KOH activation at different temperature and the post-heating in Ar. These activated graphene monoliths were characterized by N₂ adsorption at 77 K, X-ray diffraction and Raman spectroscopy. Water adsorption isotherms show a typical hydrophobicity below P/P ₀ = 0.5 and a marked hydrophilicity above P/P ₀ = 0.6, which depends on the pore width. In the water adsorption isotherms of porous graphene monoliths activated at different temperature, the higher the activation temperature, the larger the rising P/P ₀. No essential change in the shape of the water adsorption isotherm for the post-heated nanoporous graphene monoliths is observed except for the decrease in water adsorption amount with higher post-heating temperature. The linear relationship between the saturated water adsorption and pore volume whose width is smaller than 4 nm indicates clearly that water molecules are adsorbed in small mesopores by the cluster-associated filling mechanism.     

Enhanced Photocatalytic Degradation of Methylene Blue over Hexagonal WO<Subscript>3</Subscript>/Graphene under Visible-Light Irradiation

A series of composites containing hexagonal tungsten trioxide (h-WO₃) and reduced graphene oxide (rGO) sheets are synthesized via a modified one-step hydrothermal route without assisted additive. The composites are characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and UV-vis absorption spectroscopy. The new procedure made it possible to increase the reduction degree of GO. Based on the evidence presented hexagonal WO₃ grows on the surface of graphene through chemical interactions with the surface. The visible-light photocatalytic degradation of methylene blue shows that the h-WO₃/rGO composites exhibit superior photocatalytic performance of 96% with a maximum degradation rate achieved under visible-light irradiation for 6 h. The speculations concerning the mechanism of photocatalytic reactions are discussed. The improved photocatalytic activity can be accounted for by the increased adsorption toward chemical species, the enhanced light absorption and an efficient separation of photogenerated electron-hole pairs and transfer of charge carriers.     

Effective Removal of Nitrotoluene Compounds from Aqueous Solution Using Magnetic-Activated Carbon Nanocomposites (<Emphasis Type="Italic">m</Emphasis>-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@ACCs)

In this study, regular-shaped magnetic-activated carbon nanocomposite (m-Fe₃O₄@ACCs) was synthesized and characterized with X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and the vibrating sample magnetometer (VSM) and was used as adsorbents for the removal of nitrotoluene compounds (NTCs) from water and industrial wastewater. The effective parameters on adsorption process, such as solution pH, shaking speed, contact time, and adsorbent dosage were optimized and the optimum amounts were 7 300 rpm, 10 min, and 1.2 g L^–1, respectively. The contact time and adsorbent dosage are dependent parameters and hence were studied simultaneously. The results showed no significant loss in the adsorption capacity, and the adsorption efficiency of m-Fe₃O₄@ACCs could still be 90% in the 9th cycle. The equilibrium adsorption isotherm followed the Langmuir isotherm model describes the monolayer adsorption of NTCs on m-Fe₃O₄@ACCs, and the maximum adsorption capacities (q_m) for 2-nitrotolouene, 2,6-dinitrotoluene, 2,4-dinitrotoluene, and 3,4-dinitrotoluene were found to be 144.93, 142.86, 166.67, and 153.85 mg g^?l, respectively. The proposed process was successfully applied for the removal of NTCs from tap water and nitration process wastewater.     

Investigation of structural and textural properties of Ge<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript>MoO<Subscript>3</Subscript> system,promising catalyst for photocatalytic applications

The main objective of this work is to control the structural, textural and electrical properties of the system prepared by mixing molybdenum oxide with different amounts of germanium. The system is expected to be suitable as a catalyst for the photodegradation of methyl red (one of the dyes group) and the results of this study can throw some light on the relationship between the properties of this system and the extent of the dye degradation as indicated by the measurements of the photocatalytic activity. The composite materials (Ge_xMoO₃) were prepared by solid-state reaction between germanium and molybdenum oxide. The mixtures were made in Ge/MoO₃ molar ratios of 0.01, 0.05, 0.1, 0.2, 0.5, and 1.0. The reaction was conducted in air at 700°C. The prepared samples were characterized by X-ray powder diffraction, micro-Raman spectroscopy, nitrogen adsorption measurements, diffuse reflectance spectrometry and UV-Vis absorption spectrophotometry. The addition of germanium has affected the photocatalytic activity of MoO₃ as evidenced by an increase in the degradation extent of methyl red from about 14% (for pure oxide) to about 97% for Ge_xMoO₃ (x = 1). An enhancement in the photocatalytic activity was attributed to the change in the band gap and modification of the textural properties associated with the formation of Ge_xMoO₃ composites.     

Hydrogen physisorption energies for bumpy,saturated, nitrogen-doped single-walled carbon nanotubes

Finite saturated regular carbon nanotubes (CNTs) are predicted to exhibit higher capacity as hydrogen storage media compared to unsaturated regular CNTs. In the present study, molecular hydrogen physisorption energies (MHPEs) for finite saturated and unsaturated bumpy defected CNTs were calculated by density functional theory (DFT-D3) methods at the B3LYP/6-31G(d) theory level, with rigorous inclusion of van der Waals interactions. The calculated MHPEs for both regular and bumpy defected armchair, chiral and zigzag CNTs with similar diameters and lengths, with and without nitrogen doping, were compared in terms of Eph/H₂, defined as the MHPE per hydrogen molecule adsorbed inside the nanotube. For all studied systems, Eph/H₂ increased with the number of physisorbed hydrogen molecules. Nitrogen doping of regular and bumpy CNTs resulted in an increase in the Eph/H₂ values, with the exception of bumpy chiral nanotubes. The results of this study demonstrate that bumpy defects are important nanotube structural features whose effects depend on nanotube chirality. For instance, bumpy defects were beneficial for undoped and doped zigzag nanotubes, resulting in a decrease in Eph/H₂ values for regular structures from 0.5 and 0.74 to 0.26 and 0.42 eV, respectively. By contrast, for doped armchair regular structures with an Eph/H₂ value of 0.38 eV, bumpy defects increased Eph/H₂ to 0.45 eV. These Eph/H₂ values for bumpy doped armchair and the zigzag nanotubes are all within the range of 0.1–0.5 eV/H₂ reported as ideal for reversible hydrogen storage under environmental conditions.     

Crystal structures of a family of layered coordination polymers containing divalent metal ions (Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) and the 3-amino 4-methyl benzoate ion

The syntheses and crystal structures of the layered coordination polymers M(C₈H₈NO₂)₂ [M = Mn (1), Co (2), Ni (3) and Zn (4)] are described. These isostructural compounds contain centrosymmetric trans-MN₂O₄ octahedra as parts of infinite sheets; the ligand bonds to three adjacent metal ions in μ³-N,O,O′ mode from both its carboxylate O atoms and its amine N atom. In each case, weak intra-sheet N–H?O and C–H?O hydrogen bonds may help to consolidate the structure. Crystal data: 1, C₁₆H₁₆MnN₂O₄, M _r = 355.25, monoclinic, P2₁/c (No. 14), a = 10.6534(2) Å, b = 4.3990(1) Å, c = 15.5733(5) Å, β = 95.1827(10)°, V = 726.85(3) ų, Z = 2, R(F) = 0.026, wR(F ²) = 0.067. 2, C₁₆H₁₆CoN₂O₄, M _r = 359.24, monoclinic, P2₁/c (No. 14), a = 10.6131(10) Å, b = 4.3374(4) Å, c = 15.3556(17) Å, β = 95.473(4)°, V = 703.65(12) ų, Z = 2, R(F) = 0.041, wR(F ²) = 0.091. 3, C₁₆H₁₆N₂NiO₄, M _r = 359.02, monoclinic, P2₁/c (No. 14), a = 10.6374(4) Å, b = 4.2964(2) Å, c = 15.2827(8) Å, β = 95.9744(14)°, V = 694.66(6) ų, Z = 2, R(F) = 0.028, wR(F ²) = 0.070. 4, C₁₆H₁₆N₂O₄Zn, M _r = 365.68, monoclinic, P2₁/c (No. 14), a = 10.6385(5) Å, b = 4.2967(3) Å, c = 15.2844(8) Å, β = 95.941(3)°, V = 694.89(7) ų, Z = 2, R(F) = 0.038, wR(F ²) = 0.107.     

Sol-gel synthesis of ZnO/Zn<Subscript>2-x</Subscript>Fe<Subscript>x</Subscript>TiO<Subscript>4</Subscript> powders: structural properties,electrical conductivity and dielectric behavior

The aim of this work was an investigation of structural and electrical properties of ZnO/Zn_2-xFe_xTiO₄ (x?=?0.7, 1, 1.4) powders. The compounds obtained by sol-gel method are characterized by several techniques: X-ray diffraction (XRD), N₂ adsorption–desorption isotherms, scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), electrical and dielectrical measurements. The XRD, SEM and XPS analysis confirmed the formation of ZnFeTiO₄ inverse spinel structure. The electrical and dielectrical properties of ZnO/Zn_2-xFe_xTiO₄ (x?=?0.7, 1, 1.4) were measured by impedance spectroscopy, revealing a decrease in the electrical conductivity and the dielectric constant with Fe content.

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Low-melting salts with the [Cr<Superscript>III</Superscript>(NCS)<Subscript>4</Subscript>(1,10-phenanthroline)]<Superscript>−</Superscript> complex anion: Syntheses,properties, and structures

Four new low melting salts, “Ionic Liquids” consisting of the [Cr^III(NCS)₄(Phen)]^? complex monoanion and imidazolium based cations A, with A = 1-ethyl-3-methylimidazolium (EMIm), 1-butyl-3-methylimidazolium (BMIm), 1,3-dimethyl-2,4,5-triphenylimidazolium (DML), and 1,2,3,4,5-pentamethyl-imidazolium (PMIm), were investigated. Single-crystal X-ray investigations established the structures of the four compounds. (EMIm)[Cr(NCS)₄(Phen)] (I): triclinic, \(P\bar 1\), a = 8.1382(6), b = 10.4760(8), c = 16.003(1) Å, α = 90.330(4)°, β = 94.759(4)°, γ = 107.305(4)°, Z = 2, R ₁(F)/wR ₂(F ²) = 0.0650/0.1770; (BMIm)[Cr(NCS)₄(Phen)] (II): triclinic, \(P\bar 1\), a = 8.5545(4), b = 9.8620(4), c = 16.6762(6) Å, α = 92.503(2)°, β = 97.517(2)°, γ = 91.249(2)°, Z = 2, R ₁(F)/wR ₂(F ²) = 0.0393/0.0848; (DML)[Cr(NCS)₄(Phen)] · C₃H₆O (III): triclinic, \(P\bar 1\), a = 11.0475(9), b = 13.589(1), c = 14.582(1) Å, α = 83.013(4)°, β = 87.116(4)°, γ = 70.333(5)°, Z = 2, R ₁(F)/wR ₂(F ²) = 0.0407/0.1023; (PMIm)[Cr(NCS)₄(Phen)] · C₃H₆O (IV): orthorhombic, Pbca, a = 17.379(1), b = 16.514(1), c = 22.304(1) Å, Z = 8, R ₁(F)/wR ₂(F ²) = 0.0460/0.1107 (in addition III and IV contain co-crystallized acetone molecules). Each compound was characterized by elemental analysis, NMR, IR, und UV-Vis spectroscopy. Magnetic properties were derived from NMR investigations (EVANS method). All four compounds are paramagnetic with effective magnetic moments of spin-only Cr^III. Melting points were obtained from DSC measurements. All melting points are higher than required for “Ionic Liquids”, but nevertheless “low” for molten salts.     

Solid solutions (Ru,Nb)Sr<Subscript>2</Subscript>(Sm<Subscript>1.4</Subscript>Ce<Subscript>0.6</Subscript>)Cu<Subscript>2</Subscript>O<Subscript>10−δ</Subscript>: Synthesis,structure, and properties

Solid solutions of as-batch composition (Ru_1?x Nb _x )Sr₂(Sm_1.4Ce_0.6)Cu₂O_10?δ (the Ru,Nb)-1222 phase), where x = 0.0, 0.25, 0.50, 0.75, or 1.00, have been synthesized and characterized by X-ray diffraction. A correlation is proposed between the refined composition of the Ru-1222 and Nb-1222 phases and their structural features. With increasing oxygen concentration in the Ru-1222 phase, the superconducting transition temperature increases from T _c = 28 to T _c = 34 K. The composition and magnetic properties of the Ru-1222 phase are affected by the batch composition: unlike in Ru + RuO₂ mixtures, the presence of ruthenium in the batch decreases the oxygen proportion and increases the magnetic ordering temperature T _m; the phase of as-batch composition NbSr₂(Sm_1.4Ce_0.6)Cu₂O_10?δ is paramagnetic.     

Structure and thermal properties of a novel volatile bis(1,1,1-trifluoro-5,5-dimethyl-3-hexene-4-imino-2-onate) platinum(II) compound

A novel volatile Pt(II)β-iminoketonate complex is synthesized. β-Aminovinylketone H(i-ptac) = [CF₃–C(O)–CH=C(NH₂)–C(CH₃)₃] is used as a ligand. The XRD method is used to determine the structures of the ligand and the complex. The crystallographic data for C₁₆H₂₂F₆N₂O₂Pt are as follows: a = 10.0716(4) Å, b = 10.9572(4) Å, c = 9.6322(4) Å, β = 110.9010(10)°, space group С2/m, Z = 2, R = 0.011. The platinum atom has a square planar coordination with two oxygen and two nitrogen atoms of two bidentately linked ketoiminate ligands in trans-position; the PtO₂N₂ coordination site is formed.     

Nanocrystalline Calcium Carbonate Hydroxyapatites Containing Multiwall Carbon Nanotubes: Synthesis and Physicochemical Characterization

Nanocomposites (NCs) based on carbonated calcium hydroxyapatite (CHA) (bioapatite, an analogue of the inorganic component of mammalian bone tissue), carbonate apatite (Ca₁₀(PO₄)₆CO₃, CA), and multiwall carbon nanotubes (CNTs) are prepared in the system CaCl₂–(NH₄)₂HPO₄–NH₄HCO₃–NH₃–CNT–H₂O (25°C) by coprecipitation of calcium and phosphorus salts with CNTs from aqueous solutions. The physicochemical properties of nanocomposites are studied as dependent on their formation conditions and composition using the solubility (residual concentrations) method and pH measurements. The composition, crystal structure, morphology, spectroscopic and thermal characteristics of the synthesized CHA/CNT and CA/CNT NCs are determined using chemical analysis, X-ray powder diffraction, thermal analysis, and IR spectroscopy. Either CHA/CNT NCs of composition Ca₁₀(PO₄)₆(CO₃)_x(OH)_2–2х · yCNT · zH₂O, where х = 0.2; 0.5; 0.8; y = 1, 2, 3; z = 6.8–10.8, or (when х = 1) CA/CNT NCs of composition Ca₁₀(PO₄)₆CO₃ · yCNT · zH₂O, where y = 1–3; z = 6.9–10.8, are formed as the carbonate and CNT contents of the NC increase. Our results favor the understanding of the effect of carbonization and CNTs on the metabolic formation of native bone tissue apatite and can be used for the design of efficient ceramics for bone implants.     

Thermodynamic characteristics of the dissolution of glycine,glycylglycine, and glycylglycylglycine in aqueous solutions of sodium dodecyl sulfate at <Emphasis Type="Italic">Т</Emphasis> = 298.15 K

the enthalpies of dissolution of glycine (Gly), glycylglycine (GlyGly), and glycylglycylglycine (GlyGlyGly) are measured in aqueous solutions of sodium dodecyl sulfate (SDS) at SDS concentrations m = 0–0.7 mol kg^?1 and Т = 298.15 K by means of calorimetry. The obtained data are used to calculate the standard values of enthalpies of dissolution (Δ_sol H ^m ) and enthalpies of transfer (Δ_tr H ^m ) of glycine and its oligomers from water to SDS aqueous solutions. The dependences of Δ_sol H ^m and Δ_tr H ^m on SDS concentration in an aqueous solution at a constant concentration of glycine and its oligomers are determined. A comparative analysis of the thermodynamic characteristics of Gly, GlyGly, and GlyGlyGly transfer within the studied range of SDS concentrations is performed. The results are interpreted in terms of ion–ion, ion–polar, and hydrophobic interactions between SDS and molecules of glycine and its oligomers.     

Investigation of the α-BiO<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript>F<Subscript>3 − 2<Emphasis Type="Italic">y</Emphasis></Subscript>-based tysonite-type solid solutions by X-ray diffraction and impedance spectroscopy

Tysonite solid solutions Bi_{1 ? x} M _x (O, F)_{3 ? d} (M = Na, Sr, or Nd) based on α-BiO _y F_{3 ? 2y} were prepared by solid-state synthesis at 873 K with subsequent quenching to ice-cold water. Aliovalent substitutions in both the cation and anion sublattices (M ⁿ⁺ → Bi³⁺ and O^2? → F^?) made it possible to vary the anion-vacancy density. The solid solutions were characterized by X-ray diffraction and impedance spectroscopy. The homogeneity regions for the tysonite solid solution were determined; triangulation schemes at 873 K were suggested for the systems BiF₃-BiOF-NaBiF₄ and BiF₃-BiOF-SrF₂, and a scheme of the subsolidus phase diagram for the system BiO_0.1F_2.8-NdF₃ was suggested. In the system BiO_0.1F_2.8-NdF₃, the transition temperature from the low-symmetry tysonite phase (phase II, space group P \(\overline 3 \) c1, Z = 6) to the high-symmetry one (phase I, space group P6₃/mmc, Z = 2) decreases with increasing anion-vacancy density. Conductivity measurements were performed in the temperature range 300–523 K and the frequency range from 5 to 1 × 10⁶ Hz. The conductivity of samples in the system BiO_0.1F_2.8-NdF₃ increases with increasing bismuth-ion and anion-vacancy concentrations.     

NaF-CaF<Subscript>2</Subscript>-YbF<Subscript>3</Subscript> phase diagram

Vertical sections CaF₂-Na_0.4Yb_0.6F_2.2 and NaF-Ca_0.75Yb_0.25F_2.25 of the system NaF-CaF₂-YbF₃ were studied by differential thermal analysis. A fluorite solid solution belt between phases of variable composition Ca_1?x Yb _x F_2+x and Na_0.5?x Yb_0.5+x F_2+2x was discovered. A liquidus-surface projection was constructed. The solidification character of the solid solution is unfavorable for growth of optical-quality ternary mixed crystals.