Effect of temperature on the electrical properties of lanthanum ferrite.

Electric and dielectric properties of lanthanum ferrite were investigated by the alternating current impedance spectroscopy. Results reveal that LaFeO3 exhibits a non-Debye type relaxation. High values of ε' were obtained at low frequency. Such behavior was explained based on the Maxwell-Wagner polarization model. Furthermore, a low dielectric loss was obtained at high frequencies indicating that the obtained compound is an important candidate for nonlinear optical application. The variation of the AC conductivity with frequency at different temperatures obeys the universal Jonscher's power law. The decreasing trend of the exponent s with temperature increase suggests that the correlated barrier hopping model is adequate to describe the conduction mechanism in LaFeO3. Furthermore, the density of the localized states N(Ef) at the Fermi level was calculated at different temperatures. Results reveal an increase in N(Ef) with temperature increase. Such behavior explains the observed increase in σac.

Co2SnO4 nanoparticles as a high performance catalyst for oxidative degradation of rhodamine B dye and pentachlorophenol by activation of peroxymonosulfate.

Spinel Co2SnO4 nanoparticles are synthesized by a facile hydrothermal route in alkaline solution using SnCl4 and CoCl2 as precursors. The structure, morphology and chemical composition of the nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The catalytic performance of the Co2SnO4 nanoparticles is thoroughly evaluated for peroxymonosulfate (PMS) activation for removal of rhodamine B (RhB) and pentachlorophenol (PCP) from water. The influence of different process parameters on the RhB degradation efficiency is examined and the catalytic stability is evaluated. Under optimized conditions, the Co2SnO4/PMS system is very efficient with a full degradation of RhB and PCP in less than 10 min at room temperature, as revealed by high performance liquid chromatography (HPLC) analysis. Quenching experiments suggested that sulfate radicals (SO4˙-) are the main active species in the degradation process. Moreover, the Co2SnO4 catalyst is stable without any apparent activity loss after 5 cycling runs.

Hydrothermal synthesis of ZTO/graphene nanocomposite with excellent photocatalytic activity under visible light irradiation.

A facile and efficient one-step hydrothermal approach for the synthesis of Zn2SnO4 nanoparticles/reduced graphene oxide (ZTO/rGO) nanocomposites using zinc acetate, tin chloride and graphene oxide (GO) as precursors, and sodium hydroxide as reducing agent has been developed. This approach allows simultaneous reduction of GO and growth of spinel ZTO nanoparticles (NPs) on the rGO sheets. The morphology and microstructure characterizations of ZTO/rGO nanocomposites revealed that this method leads to close interfacial contact of ZTO NPs and rGO and efficient dispersion of ZTO NPs on the surface of rGO sheets. The photocatalytic activity of the ZTO/rGO nanocomposite was investigated for the reduction of rhodamine B under visible light irradiation. Compared to pure ZTO NPs, ZTO/rGO nanocomposite exhibited superior photocatalytic activity with a full degradation of rhodamine B within 15min. The enhanced photocatalytic performance of ZTO/rGO was mainly attributed to excellent electron trapping and effective adsorption properties of rGO.

Hydrothermal synthesis, phase structure, optical and photocatalytic properties of Zn2SnO4 nanoparticles.

Zinc stannate (Zn2SnO4 or ZTO) nanoparticles were synthesized via hydrothermal method using NaOH as a mineralizer. X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) of the synthesized ZTO nanoparticles revealed the formation of highly pure ZTO phase with the spinel-like structure. The nanoparticles have spherical shape with an average size of about 25 nm. The Raman spectrum of the sample was dominated by the A(1g) vibration mode of pure ZTO phase. From UV-Vis measurement, a band gap E(g) of 3.465 eV was determined. The photocatalytic activity of the ZTO nanoparticles was evaluated for the photodegradation of rhodamine B (RhB) under visible light irradiation. The influence of catalyst concentration and irradiation time on the photocatalytic process was investigated. The ZTO catalyst showed the best photocatalytic performance at a concentration of 0.2 g/L, and the photodecomposition of RhB followed first-order kinetics with a rate constant k=0.0249 min(-1). The ZTO-assisted photocatalytic degradation of RhB occurred via two competitive processes: a photocatalytic process and a photosensitized process. The detection of hydroxyl radicals by fluorescence measurements suggests that these species play an important role in the photocatalytic process.

LiHo(PO(3))(4).

Lithium holmium(III) polyphosphate(V), LiHo(PO(3))(4), belongs to the type I of polyphosphates with general formula ALn(PO(3))(4), where A is a monovalent cation and Ln is a trivalent rare earth cation. In the crystal structure, the polyphosphate chains spread along the b-axis direction, with a repeat period of four tetra-hedra and 2(1) inter-nal symmetry. The Li and Ho atoms are both located on twofold rotation axes and are surrounded by four and eight O atoms, leading to a distorted tetra-hedral and dodeca-hedral coordination, respectively. The HoO(8) polyhedra are isolated from each other, the closest Ho⋯Ho distance being 5.570 (1) Å.

Silver europium(III) polyphosphate.

Europium(III) silver polyphosphate, AgEu(PO(3))(4), was prepared by the flux method. The atomic arrangement is built up by infinite (PO(3))(n) chains (periodicity of 4) extending along the c axis. These chains are joined to each other by EuO(8) dodeca-hedra. The Ag(+) cations are located in the voids of this arrangement and are surrounded by five oxygen atoms in a distorted [4+1] coordination.

Lutetium ultraphosphate.

The structure of the title compound, LuP(5)O(14), comprises puckered eight-membered PO(4) rings linked by the lutetium cations in a complex way, forming a three-dimensional framework. Each eight-membered phosphate ring shares a bridging tetra-hedron with each of four adjacent tetra-hedra, to form layers of PO(4) tetra-hedra. These layers are c/2 in thickness and parallel to the ab plane. Each Lu ion is contained in one such layer, forming bonds to six O atoms in that layer and also to one O atom belonging to a tetra-hedron in each of the layers lying above and below it. The LuO(8) polyhedra are isolated from one another, since they share no common atoms. The Lu ions lie on twofold axes (special position 4e) and the shortest Lu⋯Lu distance is 5.703 (1) Å.

A monoclinic polymorph of KY(PO(3))(4).

The title compound, potassium yttrium polyphosphate, KY(PO(3))(4), was synthesized using the flux method. The atomic arrangement consists of an infinite long-chain polyphosphate organization. Chains, with a period of four PO(4) tetra-hedra, run along the a-axis direction. Two other polymorphs of this phosphate are known, in space groups P21/n and C2/c.

LiDy(PO(3))(4).

Single crystals of lithium dysprosium polyphosphate, LiDy(PO(3))(4), were prepared by the flux method. The atomic arrangement is built up by infinite (PO(3))(n) chains extending along the b axis. Dy(3+) and Li(+) cations alternate in the middle of four such chains, with Dy⋯Li distances of 3.54 (1) and 3.48 (1) Å. The DyO(8) dodeca-hedra and LiO(4) tetra-hedra deviate significantly from the ideal geometry. Both Dy and Li occupy special positions (Wyckoff position 4e, site symmetry 2).

A new polymorph of Lu(PO(3))(3).

A new polymorph of lutetium polyphosphate, Lu(PO(3))(3), was found to be isotypic with the trigonal form of Yb(PO(3))(3). Two of the three Lu atoms occupy special positions (Wyckoff positions 3a and 3b, site symmetry ). The atomic arrangement consists of infinite helical polyphosphate chains running along the c axis, with a repeat period of 12 PO(4) tetra-hedra, joined with LuO(6) octa-hedra.

[Preparation and structural study of NH(4)Gd(PO(3))(4) and NH(4)GdP(4)O(12)]. / Préparation et étude structurale de NH(4)Gd(PO(3))(4) et NH(4)GdP(4)O(12).

Ammonium gadolinium polyphosphate, NH(4)Gd(PO(3))(4), (I), and ammonium gadolinium cyclotetraphosphate, NH(4)GdP(4)O(12), (II), were synthesized by flux growth with excess (NH(4))(2)HPO(4). In (I), the PO(4) tetrahedra share vertices to produce corrugated ribbons along the c direction, while in (II) they form P(4)O(12) rings arranged in layers perpendicular to the c axis. In both structures, isolated GdO(8) polyhedra link the phosphate anions into a three-dimensional framework with channels containing the NH(4)(+) cations. The Gd and N atoms are located in general positions in (I) and on twofold axes in (II).