Synthesis, spectroscopic, structural and thermal characterizations of [(C7H6NO4)2TeBr6·4H2O]

AbstractTellurium (IV) complexes with pyridine-2,6-dicarboxylate ligand were synthesized by slow evaporation from aqueous solutions yielding a new compound: [(C7H6NO4)2TeBr6·4H2O]. The structure of this compound was solved and refined by single-crystal X-ray diffraction. The compound is centrosymmetric P21/c (N°: 14) with the parameters a=8.875(5)Å, b=15.174(5)Å, c=10.199(5)Å, β=94.271° (5) and Z=2. The structure consists of isolated H2O, isolated [TeBr6]2− octahedral anions and (pyridine-2,6-dicarboxylate) [C7H6NO4]+ cations. The stability of the structure was ensured by ionic and hydrogen bonding contacts (N–H⋯Br and O–H⋯Br) and Van-Der Walls interaction. The thermal decomposition of the compound was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The FTIR and Raman spectroscopy at different temperatures confirm the existence of vibrational modes that correspond to the organic, inorganic and water molecular groups. Additionally, the UV–Vis diffuse reflectance spectrum was recorded in order to investigate the band gap nature. The measurements show that this compound exhibits a semiconducting behavior with an optical band gap of 2.66eV

Mild hydrothermal synthesis of the two compounds [SrZn2(SeO3)3] and [SrZn0.68Cu0.32(SeO3)2]: Structural characterization, spectroscopic and magnetic studies

Two new selenite SrZn2(SeO3)3 (1) and SrZn0.68Cu0.32(SeO3)2 (2) were synthesized by the hydrothermal technique under autogeneous pressure. The crystal structure of both compounds was solved from X-ray diffraction data. Compound (1) was crystallized in P1¯ triclinic space group. However, compound (2) was crystallized in P21/n monoclinic space group. Infrared studies confirm the presence of all vibration bands in both structures. The temperature dependence of the magnetic susceptibility was measured in the temperature range of 10–300 K at different magnetic field intensities for both compounds. No magnetic properties were detected for compound (1). Mean while, compound (2) displayed antiferromagnetic properties. Keywords: X-ray diffraction, IR, Antiferromagnetic, Selenit

Thermal analysis, dielectric properties and conduction mechanism of Cu 1.09 Ni 0.91 (HSeO 3 ) 2 Cl 2 · 4H 2 O compound

International audienc

Synthesis, spectroscopic, structural and thermal characterizations of [(C7H6NO4)2TeBr6·4H2O]

Tellurium (IV) complexes with pyridine-2,6-dicarboxylate ligand were synthesized by slow evaporation from aqueous solutions yielding a new compound: [(C7H6NO4)2TeBr6·4H2O]. The structure of this compound was solved and refined by single-crystal X-ray diffraction. The compound is centrosymmetric P21/c (N°: 14) with the parameters a = 8.875(5) Å, b = 15.174(5) Å, c = 10.199(5) Å, β = 94.271° (5) and Z = 2. The structure consists of isolated H2O, isolated [TeBr6]2− octahedral anions and (pyridine-2,6-dicarboxylate) [C7H6NO4]+ cations. The stability of the structure was ensured by ionic and hydrogen bonding contacts (N–H⋯Br and O–H⋯Br) and Van-Der Walls interaction. The thermal decomposition of the compound was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The FTIR and Raman spectroscopy at different temperatures confirm the existence of vibrational modes that correspond to the organic, inorganic and water molecular groups. Additionally, the UV–Vis diffuse reflectance spectrum was recorded in order to investigate the band gap nature. The measurements show that this compound exhibits a semiconducting behavior with an optical band gap of 2.66 eV

New relaxor ceramic with composition BaTi1-x(Zn1/3Nb2/3)xO3

New ferroelectric ceramics of ABO3 perovskite type were synthesized in the BaTi1-x(Zn1/3Nb2/3)xO3 system by solid state reaction technique. The effect of the replacement of titanium by zinc (Zn) and niobium (Nb) in the B cationic site on structural and dielectric properties were investigated. As a function of composition, these compounds crystallize with tetragonal or cubic symmetry. The material is classical ferroelectric for 0 ≤ x ≤ 0.05 and presents a relaxor behavior for 0.075 ≤ x ≤ 0.2 and for 0.75 ≤ x ≤ 0.975. Dielectric permittivity in the temperature range from 85 to 500 K with frequencies range from 0.1 to 200 kHz, was studied. In the region when 0.75 ≤ x ≤ 0.975, ΔTm presents the important values which go more then 100 K for BaTi0.05(Zn1/3Nb2/3)0.95O3 composition with values of Tm near room temperature. These values make these ceramic compositions in the families of relaxors with interest properties for applications. © 2007 Elsevier B.V. All rights reserved

Structural and Mossbauer study of the Brownmillerite oxides LaSrMn2-xFexO5 (0 <= x <= 0.5)

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Modulation relaxor behaviour by chemical substitution in the system Ba1-xCaxTi1-y(Zn1/3Nb2/3)yO3

This paper reports the structural and dielectric properties of Ba1 - xCaxTi1 - y (Zn1/3Nb2/3)yO3 ceramics with y is fixed to 0.2 and x = 0.2 and 0.3. Single-phase solid solutions of the simples were determined by X-ray diffraction. For the solid solution, BaTi1 - y(Zn1/3Nb2/3)yO3, the evolution of dielectric behaviour from a sharp ferroelectric peak (for y < 0.075) and to ferroelectric relaxor (for 0.075 < y < 0.2) was observed with increasing of Zn and Nb concentration but in this case the temperature of the maximum of dielectric permittivity Tm and Δ Tm are lowers. To modulate this relaxor character we have substitute the Ba by Ca to increase Tm and Δ Tm