In this study, calcined ZrTe3O8 powder mixed with 7%wt of CuO was sintered at 750 degrees C. The new doped ceramic ZrTe3O8:7%CuO was synthesized using solid state reaction method and was studied with X-ray diffraction (XRD). At room temperature, the title compound crystallizes in cubic space group Ia (3) over bar, with lattice parameter a = 11.328(3) angstrom, and exhibits a complex network of interconnected closed chains built up of TeO4E (E = electronic lone pair of Te (IV) atoms). The Zr/CuO6 octahedra are inserted into these chains ensuring the stability of the structure by Zr/Cu -O-Te bonding contacts. IR and Raman spectroscopic study are employed as means to obtain preliminary structural information and confirms the presence of the ZrO6 and TeO4E groups. Optical properties of the ceramic were explored by using UV-Vis absorption. The magnetic results reveal the appearance of a weak ferromagnetic behavior at low temperature (T-C = 46.172 K). In addition, dielectric data were analyzed using real and imaginary permittivity epsilon' and epsilon '' respectively, the tan (delta) and the electrical modulus (M and M '') for the sample ZrTe3O8:7%CuO at various frequencies. The Z' and Z '' versus frequency plots are well fitted to an equivalent circuit model composed of a series combination of two parallel combinations of resistance Ri and constant phase element CPEi. (C) 2020 Elsevier B.V. All rights reserved.

The powder sample of xMnO(2)-(1-x) ZrTe3O8 (x = 7%) was prepared by the conventional solid state reaction method. X-ray diffraction showed that the compound crystallized at room temperature in the cubic fluorite structure (in a cubic unit-cell Ia (3) over bar as MTe3O8-type framework) with lattice parameter a = 11.3298(2) angstrom. The structure was built up of TeO4E (E = Electronic lone pair of Te(IV)) disphnoids and regular ZrO6 octahedra. The crystal structure cohesion was ensured via Te-O(2)-Zr and Te-O(1)-Te bridges.The Raman spectrum was dominated by a stronger band at 858 cm(-1), characteristic of Te-O(2)-Zr bridges asymmetric stretching vibration. Thus, the Te-O(2) and Zr(Mn)-O(2) bonds are chemically inequivalent and then the Te-O(2)-Zr bridges are chemically asymmetric. Magnetization measurements versus temperature in an applied magnetic field of 0.05 T were determined. The doping of Zr by Mn induces a ferro-paramagnetic transition at T = 18.5 K. The complex impedance of the xMnO(2)-(1-x) ZrTe3O8 (x = 7%) ceramics has been investigated in the temperature range 293-843 K and in the frequency range 100 Hz-1 MHz. Dielectric data were analyzed using complex permittivity (epsilon'), (epsilon") and tan (delta) for the sample at various temperatures. The conductivity follows the Arrhenius relation. (C) 2017 Elsevier B.V. All rights reserved.

Stable glasses are successfully synthesized in the TeO2-GeO2-ZnO system at 850 degrees C by the melt-quenching method and the glass forming domain is determined in the TeO2-rich part of the diagram. The thermal study, carried out using differential scanning calorimetry, reveals that the glass transition temperature, as well as the thermal stability, increases with the addition of ZnO or GeO2. Bulk glass samples are elaborated within two series of compositions, corresponding to fixed concentrations in GeO2 (respectively 5 or 10 mol. %), and to various contents in ZnO. Structural changes caused by the ZnO addition are discussed based on Raman spectroscopy data. A progressive but very moderate network depolymerization is shown with increasing amount of ZnO. However, two different regimes can be identified, depending on the ZnO content. It is believed that ZnO acts as a network modifier for compositions below 20 mol. %, and starts to participate as a glass network former over such concentration. It is well evidenced that GeO2 contributes to the increase in Young's modulus E, evaluated from ultrasonic echography measurements. In addition, this oxide favors the network reticulation detected by the decrease of the Poisson ratio and the increase of the fractal bond connectivity. However, the role of ZnO is more complicated and will be extensively discussed. The decrease in the atomic packing density C-g probably explains the global evolution of E as a function of ZnO content. The refractive indices and optical band gap energies are extracted from UV-Visible-NIR optical transmission data. For the studied glasses, it is found that the transmission threshold decreases with larger ZnO contents, reflecting the increase in the optical band gap value. Refractive index is finally seen to decrease as a function of both ZnO and GeO2 contents. Such variation is explained by the decrease of the molar electronic polarizability, and by the lower optical basicity values known for TeO3 entities in comparison to TeO4 units. (C) 2014 Elsevier Masson SAS. All rights reserved.

A glass-forming domain was evidenced and studied within the TeO2-TiO2-ZnO system. Density, glass transition temperature (T-g) and onset crystallization temperature (T-o) were measured and interpreted as a function of the zinc oxide mole fraction for relevant glasses. It was concluded that the zinc oxide favors the thermal stability of glasses. On the other hand, the impact of TiO2 addition is even more pronounced on the enhancement of the thermal stability. The optical transmission was recorded for series of glasses in the UV-Visible-NIR range. Refractive index and optical band gap were extracted from these measurements and studied as a function of the ZnO content. Linear refractive indices and optical band gap were found to decrease and increase respectively, with increasing ZnO content. The third-order non-linear susceptibility Re (X-3), measured for two series of glasses (TiO2 content was fixed either to 5 or 10 mol%), was found to progressively decrease when the ZnO concentration increases. The impact of ZnO modifier on the glass structure was discussed based on Raman spectroscopy data. We evidenced that TiO2 does not change drastically the glass network, whereas ZnO leads in a first step to the breaking of the Te-O-Te bridges, inducing network depolymerization. A further addition in ZnO leads to the formation of new Te-O-Zn and Zn-O-Zn linkages. (C) 2014 Elsevier B.V. All rights reserved.

The crystal structure of lithium–ammonium hexabromotellurate[(NH4)0.63Li0.37]2TeBr6, has been determined by X-ray single crystal analysis at room temperature. The space group is Fm 3¯ m, with a = 10.7200(12) Å. Differential scanning calorimetry reveals three anomalies at 195, 395 and 498 K. Below 195 K the phase transition leads to a tetragonally distorted structure. This low temperature phase shows an anti-ferrorotative displacement ofTeBr62- octahedra with a tilt angle 6 °. The title compound has an anti-fluorite-type arrangement ofNH4+/Li+ and octahedralTeBr62- anions.

The mixed hexabromotellurate [(NH4)(0.63)Li-0.37](2)TeBr6, presenting at room temperature a K2PtCl6-type structure with space group Fm (3) over bar m, exhibits three anomalies at 195, 395 and 498 K in the differential scanning calorimetry diagram. Different techniques: dielectric investigation, High-temperature X-ray powder diffraction and infrared spectroscopic study, in the range temperature (300-470) K are applied to explore the phase transition around 395 K. Combining XRD, dielectric and differential scanning calorimetry (DSC) results, no phase transition leading to a super-ionic conductivity phase is found. At high temperature, [(NH4)(0.63)Li-0.37](2)TeBr6 is characterized by a medium conductivity sigma(453) approximate to 10(-4) Omega(-1)m(-1).

The crystal structure of the new Li-doped material [Li0.08(NH4)0.92]2TeCl4Br2, has been determined by X-ray single crystal analysis at room temperature. The title compound crystallizes in the tetragonal space group P4/mnc, with a lattice parameters a=7.3269(3)Å and c=10.3916(5)Å, Z=2. The structure of [Li0.08(NH4)0.92]2TeCl4Br2 consists of isolated TeCl4Br2 octahedra slightly deformed in c-direction. These octahedra show a slightly rotation around the fourfold axis against the cubic arrangement of the K2PtCl6 type structure. The monovalent cations (Li+/NH4+) are located between the octahedra ensuring the stability of the structure by ionic and hydrogen bonding contacts: Li⋯Cl/Br and N–H⋯Cl/Br. Three endothermic peaks in thermal behavior were detected for this compound at 350K, 419K and 558K, by DSC experiment. The first transition was confirmed by Raman spectroscopic and IR studies. Hydrogen bonding, the nature and the degree of structure (dis)order and the mechanisms of the transitions are discussed. The dielectric constant at different frequencies and temperatures revealed a phase transition at 350K related to NH4+ reorientation and H+ diffusion.

AbstractThe A2TeX6 (A: alkali metal; X: halogen) family represents a vast class of semiconductors and the influence of both cation and anion substitutions on the structure and on the bonding within the TeX62‐ anions is of great interest.

The structure of [Cs0.8(NH4)0.2]2TeBr5.6Cl0.4 has been determined from conventional X-ray powder diffraction data, by Rietveld method, in Fm−3m cubic space group [a=10.6798(6)Å, Z=4] and was further investigated by IR spectroscopy. The refinement of the structure led to final factor χ2=0.068. The studied [Cs0.8(NH4)0.2]2TeBr5.6Cl0.4 compound has an antifluorite-type arrangement. The tellurium atoms are surrounded by a disordered of chlorine or bromine atoms octahedron. The Cs or N atoms are located between the octahedral ensuring the stability of the structure by ionic and hydrogen bonding. Two endothermic peaks in thermal behaviour were detected for this compound at 328K and 461K, by DSC experiment. An IR spectroscopic study is employed as a means to obtain preliminary structural information and shows the presence of the NH4+ groups.

The crystal structure of rubidium-ammonium hexachlorotellurate [Rb0.94(NH4)0.06]2TeCl6 was determined by X-ray single crystal analysis at room temperature. The space group is Fm3m with the lattice parameter a = 10.2503(5) Å and Z = 4. The refinement converged to R(F) = 0.015 and wR(F 2) = 0.032. As in the studied [Rb0.94(NH4)0.06]2TeCl6 family, this compound has an antifluorite-type arrangement. Tellurium atoms are surrounded by an octahedron of chlorine atoms. The Rb or N atoms are located between TeCl 2 6 octahedra ensuring the stabilization of the structure by ionic and hydrogen bonding contacts N-HCl. The substitution of rubidium by ammonium groups does not affect the structural arrangement, but it leads to a decrease in the a lattice cell dimension. IR and Raman spectroscopic studies at room temperature were performed to confirm the X-ray crystallographic results.

The differential scanning calorimetry diagram of [Li0.2(NH4)0.8]2TeCl6 showed one anomaly at 526 K accompanied with a shoulder at 505 K.

The crystal structure of cesium ammonium hexachlorotellurate [Cs0.86(NH4)0.14]2TeCl6, has been determined using X-ray powder diffraction techniques. At room temperature, the title compound crystallizes in the cubic space groupFm3m, with a lattice parametera=10.470(17) Å. The Rietveld refinement of the structure led to final confidence factorsRp=0.0338 andRwp=0.0487. The structure of [Cs0.86(NH4)0.14]2TeCl6belongs to the large family of K2PtCl6-related structures. The H atoms of the ammonium group are orientated with its apex toward Te atoms as seen in the related compound (NH4)2SiF6. An IR spectroscopic study was performed to confirm the results of the diffraction method, notably concerning the presence of the ammonium group.

The crystal structure of rubidium-ammonium hexachlorotellurate [Rb-0.8(NH4)(0.2)](2)TeCl6, has been determined by X-ray single crystal analysis at room and low temperatures (260 K). The space group at both temperatures is Fm (3) over barm with a approximate to 10.2 Angstrom, Z = 4. The refinement converged, at room and low temperatures to R = 0.021 and 0.011, respectively. The title compound has an antifluorite-type arrangement of NH4+/Rb+ and octahedral TeCl62- anions. At room temperature, the H atoms belonging to ammonium group exhibit a six-fold disorder about [111]. Decreasing of temperature induces an ordering of NH4+, evidenced by a three-fold H-disorder and a decreasing of the equivalent thermal values. IR and Raman spectroscopic studies at room temperature were performed to confirm results of the X-ray diffraction. (C) 2004 Elsevier B.V. All rights reserved.

Cl6H6.4Li0.4N1.6Te, cubic, Fm (3) over barm (No. 225), a = 10.357(2) Angstrom, V = 1111.0 Angstrom(3), Z = 4, R-gt(F) = 0.060, wR(ref)(F-2) = 0.149, T = 299 K.