Phase Transition and Electrical Properties in Cs2SeO4.Te(OH)6

Dielectric investigations in the temperature and frequency 300- 600 K and 0,1KHz–13MHz, respectively, show that cesium selenate tellurate Cs2SeO4.Te(OH)6 (CsSeTe) exhibits two phase transitions at 490 and 525 K. The a.c. complex impedance measurements performed on CsSeTe material show an important level of conductivity at high temperature, attributed to the motion of H+ proton. This behavior is in agreement with the presence of the super- protonic phase transition in CsSeTe compound at 525K. This assignment was confirmed by the analysis of the M"/M"max spectra. The temperature dependences of ε΄r and tanδ indicate that the anomaly at 490K is attributed to a ferroelectric-paraelectric phase transition. Thermal analysis at high temperature, DSC, DTA, TG,  Ms/z= 18 and Ms/z= 32 confirm the presence of the two transitions already cited, the temperature and the nature of the decomposition. Â

Thermal analysis, X-ray diffraction, spectroscopy studies and magnetic properties of the new compound Tl2HAsO4.Te(OH)6

The Tl2HAsO4.Te(OH)6 (TlAsTe) compound crystallizes in the triclinic system P1 with unit cell parameters: a= 7.100(10) Å, b= 7.281(13) Å, c= 8.383(11) Å, α= 76.91(1)°, β= 87.16(1)°, γ= 66.96(2)°, Z= 2 and V= 388.19(1) Å3. This new structure can be described as a lamellar one with the atomic arrangement being built by planes of Te(OH)6 octahedra alterning with planes of arsenate tetrahedra. Raman and infrared spectra recorded at room temperature confirm the presence of As  and Te  groups and characterize the hydrogen bonds present in the crystal lattice. Differential scanning calorimerty shows the presence of three-phase transitions at 396 K, 408 K and 430 K present in the title compound. Typical thermal analyses, such as differential thermal analysis and thermogravimetry show that the decomposition of this material starts at about T= 445 K. Magnetization curve of Tl2HAsO4·Te(OH)6 substance have revealed a diamagnetic response overall temperature range studied

Ischemic Colitis Revealing Polyarteritis Nodosa

Ischemic colitis is one of the most common intestinal ischemic injuries. It results from impaired perfusion of blood to the bowel and is rarely caused by vasculitis. We report a case of ischemic colitis revealing polyarteritis nodosa (PAN) in a 55-year-old man. Histological examination of the resected colon led to the diagnosis of PAN

Optical, thermal, vibrational and structural investigation to characterize phase transitions in the ammonium sulfate tellurate

The thermal study DSC, TG, dTG, DTA, Ms 18/H2O and Ms 15/NH3 reveal the presence of two-phase transitions at T = 401 K and 463 K before the decomposition which takes place at T = 485 K through the check of five water and two ammonia molecules. The structural study at high temperature T = 410 K and the spectroscopic evolution with the temperature prove that the first transition is of order-disorder and structural type. Basically, using the Tauc model, we determined the direct optical band gap Eg=2.11 eV so as to characterize the optical properties.Peer reviewe

Structure, Thermal Behavior and Characterization of a New Hybrid Iron Fluoride FeF4(2,2 '-bipyridine)(H2O)(2)

New crystal of FeF4(2,2′-bipyridine)(H2O)2 was prepared by hydrothermal synthesis. Crystalline structure determination is performed from single crystal X-ray diffraction data. The unit cell is monoclinic space group P21/n, with cell parameters a=0.9046(5) nm, b=0.7502(5) nm, c=1.9539(5) nm, β=93.307(5)°, V=1.3238(12) nm3 and Z=4. The structure of FeF4(2,2′-bipyridine)(H2O)2 is built up from FeF4N2 octahedra coordinated by two nitrogen atoms of the 2,2′-bipyridine molecules, and four fluorine atoms as well as uncoordinated H2O molecules. Thermal analysis of the title compound showed that the decomposition introduced four steps. IR spectra confirmed the presence of 2,2′-bipyridine molecules. The optical absorption was measured at the corresponding λmax using UV-Vis diffuse reflectance spectrum.Supported by the Project from the Ministry of Superior Education and the Research of Tunisia and Spanish MINECO (No. MAT2006-150AM).Peer Reviewe

Structural, thermal behavior and vibrational studies of the new rubidium arsenate tellurate Rb2HAsO4·Te(OH)6

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X-ray and electrical conductivity studies in the rubidium selenate tellurate

The new salt Rb2SeO4·Te(OH)6 (RbSeTe) is monoclinic P21/c. The unit cell parameters are: a = 13.783(2) Å, b = 6.791(3) Å, c = 11.713(2) Å, β = 107.23(2)°, Z = 4, V = 1047.0(5) Å3 and ρcal = 3.44 g cm−3. As it was previously described for selenate tellurate, the main feature of this atomic arrangement is the coexistence of two different types of anions (TeO66− and SeO42− groups) in the unit cell, connected by Osingle bondHcdots, three dots, centeredO hydrogen bonds which make the building of the crystal..