Synthesis, crystal structure and electrophysical properties of triple molybdates containing silver, gallium and divalent metals

A possibility of the triple molybdates formation with both NASICON-like and NaMg3In(MoO4)5 structures in the Ag2MoO4–AMoO4–Ga2(MoO4)3 (A = Mn, Co, Zn, Ni) systems was studied by powder X-ray diffraction analysis. It was established that NASICON-like phases Ag1−xA1−xGa1+x(MoO4)3 are not formed. The triple molybdates AgA3Ga(MoO4)5 (A = Mn, Co, Zn) isostructural to triclinic NaMg3In(MoO4)5 (sp. gr. P`1, Z = 2) were synthesized and characterized. The structure of the obtained compounds was refined for AgZn3Ga(MoO4)5  according to the powder data by the Rietveld method. The structure consists of MoO4 tetrahedra, couples of edge-shared M(1)O6 octahedra, and trimers of edge-shared M(2)O6-, M(3)O6- and M(4)O6 octahedra, which are linked by the common vertices to form a 3D framework. High-temperature conductivity measurements revealed that the conductivity of AgMn3Ga(MoO4)5 at 500 °С reaches 10-2 S/cm, which is close to one of the known NASICON-type ionic conductors

Mineral-Inspired Crystal Growth and Physical Properties of Na 2 Cu(SO 4 ) 2 and Review of Na 2 M (SO 4 ) 2 (H 2 O) x ( x = 0–6) Compounds

International audienceSingle crystals and polycrystalline samples of a synthetic analogue of saranchinaite, Na 2 Cu(SO 4) 2 , have been prepared by two different methods. The structural analysis revealed unusual heptahedral CuO 7 coordination [4 + 1 + 2] of Cu 2+ cations in its crystal structure. The title compound crystallizes in the noncentrosymmetric space group P2 1 and exhibits the averaged nonlinear coefficient ⟨d⟩ = 1.4[d 14 (SiO 2)] ≈ 0.5 pm/V. Electrochemical tests showed a limited electrochemical performance and low mobility of Na ions in the structure. The magnetic properties of Na 2 Cu(SO 4) 2 reflect its crystal structure with half of copper cations as mainly paramagnetic and the other half as strongly engaged in antiferromagnetic dimer interactions. Analysis of the synthesis methods for preparation of the other Na-containing anhydrous sulfates is reported. Dehydration of the Na 2 M(SO 4) 2 (H 2 O) x (x = 0−6) phases, various structure types, and the structural complexity of Na 2 M(SO 4) 2 (M = Mn, Co, Ni, Cu, Zn, Cd) compounds are also discussed

Composition dependence of the multifunctional properties of Nd-doped Bi4Ti3O12 ceramics

Sample preparation, evolution of the crystal structure with Nd content at room temperature, as well as dielectric and magnetic properties of polycrystalline Bi4-xNdxTi3O12 solid solutions (x = 0.0, 0.5, 1.0, 1.5, and 2.0) are reported. These solid solutions were structurally characterized by X-ray powder diffraction using Rietveld refinements. For x <= 1.0, the samples crystallize in an orthorhombic symmetry. The structural data could be refined using the polar orthorhombic space group B2cb. The orthorhombicity decreases with increasing Nd3+ concentration, and a paraelectric tetragonal structure (space group I4/mmm) is stabilized for x > 1. The ferroelectric Curie temperature was found to monotonously decrease with increasing Nd concentration. A polar-to-nonpolar phase transition takes place near x = 1, reflecting the existence of a morphotropic phase boundary between 1.0 < x < 1.5 at room temperature. All samples were found to be paramagnetic down to 5 K, however, the presence of significant antiferromagnetic interaction is inferred from Curie-Weiss analyses of the temperature dependence of the magnetic susceptibility of the doped samples. The effect of Nd3+ substitution on structure-property relationship is discussed and compared to that of other lanthanide cations

New Series of Red-Light Phosphor Ca9−xZnxGd0.9(PO4)7:0.1Eu3+ (x = 0–1)

In this study, a new series of phosphors, Ca9−xZnxGd0.9(PO4)7:0.1Eu3+ (x = 0.00–1.00, step dx 0.05), was synthesized, consisting of centro- and non-centrosymmetric phases with β-Ca3(PO4)2-type structure. Crystal structures with space groups R3c (0.00 ≤ x < 0.35) and R3¯c (x > 0.8) were determined using X-ray powder diffraction and the method of optical second harmonic generation. In the region 0.35 ≤ x ≤ 0.75, phases R3c and R3¯c were present simultaneously. Refinement of the Ca8ZnGd(PO4)7 crystal structure with the Rietveld method showed that 71% of Gd3+ ions are in M3 sites and 29% are in M1 sites. A luminescent spectroscopy study of Ca9−xZnxGd0.9(PO4)7:0.1Eu3+ indicated the energy transfer from the crystalline host to the Gd3+ and Eu3+ luminescent centers. The maximum Eu3+ luminescence intensity corresponds to the composition with x = 1

Iodide-Iodates M₃[IO₃]₁₂·Ag₄I, M = Bi, Tb, with a Framework Structure and High Second-Harmonic Generation Optical Response

Single crystals of two new iodide-iodates, Bi₃[IO₃]₁₂·Ag₄I and Tb₃[IO₃]₁₂·Ag₄I, are synthesized in hydrothermal systems. The anionic parts in both iodide-iodates are characterized as a complex charged framework of isolated IO₃ umbrella-like groups and large Bi­(Tb)–O polyhedra similar to those previously found in La₃[IO₃]₁₂­[IO₃]­(Pb₃O). Broad channels along the <i>c-</i>axis contain compensators: (Ag₃I)²⁺ umbrella-like groups and additional Ag⁺ ions which form Ag₄⁴⁺ tetrahedral clusters augmented with I^– halogen. New iodates possess significantly higher second-order nonlinear optical characteristics compared to the previously known lead-containing compounds REE₃[IO₃]₁₂­[IO₃]­(Pb₃O), REE = La, Pr, Nd. The difference is related to the polar ordering of umbrella-like (Ag₃I)²⁺ groups in the channels in the new iodide-iodate. Additionally, planar-coordinated Ag atoms add three Ag atoms in umbrellas forming [Ag₄I]³⁺ polar clusters in the channels

Pb6O5(NO3)2: A Nonlinear Optical Oxynitrate Structurally Based on Lead Oxide Framework

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.A high second harmonic generation response is demonstrated by a Pb6O5(NO3)2 lead oxynitrate whose identity was verified upon reinvestigation of the PbO–Pb(NO3)2 system. Its crystal structure exhibits a unique cationic [Pb6O5]2+ framework hosting orientationally ordered NO3– triangles in the channels. Easy preparation and high thermal stability (until ∼500 °C in air) suggest it to be a new promising NLO material