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Essehli R.,Laboratory of Mineral Solid and Analytical Chemistry LCSMA | El Bali B.,Laboratory of Mineral Solid and Analytical Chemistry LCSMA | Benmokhtar Said.,LCMS | Fuess H.,Sudan University of Science and Technology | And 2 more authors.
Journal of Alloys and Compounds | Year: 2010

The new mixed-anion phosphate Na4Mg3(PO4)2(P2O7) has been prepared and its structure has been determined by single crystal X-ray diffraction. The crystal structure was refined to R = 0.0290 (wR = 0.0836) for 1527 independent reflexions. This compound crystallizes in the orthorhombic non-centrosymmetric space group Pn21a with a = 17.985(2) Å, b = 6.525(9) Å, c = 10.511(1) Å, and Z = 4. The framework is built up from [PO4] tetrahedra, [P2O7] groups and [MgO6] octahedra. The three dimensional structure consists of [Mg3P2O13]∞ infinite layers parallel to the bc plane. The layers are built up from [MgO6] octahedra and [PO4] tetrahedral, they are connected along the a axis by O-P-O-P-O bridges of the diphosphate groups. Large tunnels extending along the three main crystallographic directions host four crystallographically distinct sodium cations. The infrared spectrum of Na4Mg3(PO4)2(P2O7) is interpreted on the basis of P2O7 4- and PO4 3- vibrations. The appearance of νsP-O-P in the spectrum suggests a bent P-O-P bridge for the P2O7 4- ions in the compound, which is in agreement with the X-ray data. © 2009 Elsevier B.V. All rights reserved.


Kaoua S.,LPCMI | Krimi S.,LPCMI | Pechev S.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux | Gravereau P.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux | And 3 more authors.
Journal of Solid State Chemistry | Year: 2013

A new member of the A2MP2O7 diphosphate family, Cs2MnP2O7, has been synthesized and structurally characterized. The crystal structure was determined by single crystal X-Ray diffraction. Cs2MnP2O7 crystallizes in the orthorhombic system, space group Pnma (62), with the unit cell parameters a=16.3398(3), b=5.3872(1), c=9.8872(2) Å, Z=4 and V=870.33(3) Å3. The structure parameters were refined to a final R1/wR2=0.0194/0.0441 for 1650 observed reflections. The 2D framework of Cs2MnP2O7 structure consists of P2O7 and MnO5 units. The corner-shared MnO5 and P2O7 units are alternately arranged along the b axis to form [(MnO)P2O7] chains. These chains are interconnected by an oxygen atom to form sheets parallel to the (b, c) plane. The cesium atoms are located between the sheets in 9- and 10-fold coordinated sites. The infrared and Raman vibrational spectra have been investigated. A factor group analysis leads to the determination of internal modes of (P2O7) groups. UV-visible spectrum consists of weak bands, between 340 and 700 nm, assigned to the forbidden d-d transitions of Mn2+ ion, and of a strong band around 250 nm, attributed to the OMn charge transfer. © 2012 Elsevier Inc.


Omrani R.O.,Tunis el Manar University | Krimi S.,LPCMI | Videau J.J.,CNRS Institute of Chemistry | Khattech I.,Tunis el Manar University | And 2 more authors.
Journal of Non-Crystalline Solids | Year: 2014

Two series of manganese phosphate glasses (50x/2)Na2O-xMnO-(50 - x/2)P2O5 and (50 - x)Na2O-xMnO-50P 2O5 (0 ≤ x ≤ 33 mol%), were prepared and investigated by means of density measurements, molar volume evolutions, FTIR and Raman spectroscopy, differential scanning calorimetry and calorimetric dissolution. In both series, density and glass transition temperature increase with composition. For the first series of glasses (3 ≤ O/P ≤ 3.49), spectroscopic analysis indicates that the addition of MnO content induces an evolution of structural units from Q2 to Q1 tetrahedral sites indicating the depolymerization of phosphate chains. By introducing MnO oxide into the second glass series (O/P = 3), POP linkages are disrupted, suggesting a structural changes in the vitreous network. Calorimetric dissolution of both series of glasses in 4.5% weight of H3PO 4 solution shows that the dissolution phenomenon is endothermic for the low MnO content and becomes exothermic as MnO concentration increases. This behavior may be correlated to the structural modification resulted from the depolymerization of the infinite metaphosphate chains. © 2014 Elsevier B.V.


Omrani R.O.,Tunis el Manar University | Krimi S.,LPCMI | Videau J.J.,CNRS Institute of Chemistry | Khattech I.,Tunis el Manar University | And 2 more authors.
Journal of Non-Crystalline Solids | Year: 2014

Glasses of the (50 - x/2)Na2O-xZnO-(50 - x/2)P2O 5(3 ≤ O/P ≤ 3.49) and (50 - x)Na2O-xZnO-50P 2O5 (O/P = 3) (0 ≤ x ≤ 33 mol%) compositions were prepared using the conventional melt quenching technique. The increase of density and glass transition temperature in both series is related to the reticulation of phosphate chains. For the first series of glasses, Fourier-transformed infrared (FTIR), Raman and 31P solid state magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy revealed the decrease of Q2 tetrahedral sites and the increase of phosphate dimers (Q1), indicating the shortening of phosphate chains. For the second series, FTIR and Raman spectroscopy show only the presence of Q2 tetrahedral sites. Dissolution of these series in 4.5% weight of H 3PO4 solution has been followed calorimetrically and showed that the dissolution of the first series is endothermic for the low ZnO content and becomes exothermic when x rises. This behavior is correlated to the structural modification. For the second series, the dissolution phenomenon is endothermic confirming the presence of the same structure over the whole composition range. © 2014 Elsevier B.V.


Cherbib M.A.,Tunis el Manar University | Krimi S.,LPCMI | El Jazouli A.,LCMS | Khattech I.,Tunis el Manar University | And 3 more authors.
Journal of Non-Crystalline Solids | Year: 2016

Phosphate glasses having the general formula (100-x) NaPO3-x SrO with an O/P ratio varying between 3 and 3.25 were synthesized by melt quenching technique. The glasses are studied in order to determine the influence of SrO addition on the structural and physical-chemical properties. Density, glass transition and crystallization temperatures increase with SrO content, showing the shrinking and reticulation of phosphate network. The chemical durability of the glass series is enhanced by the substitution of Na2O and P2O5 by SrO. Fourier Transform Infrared Spectroscopy and 31P Magic Angle Spinning Nuclear Magnetic Resonance spectroscopies revealed the depolymerisation of the glass network by the decrease of middle chain units to create end chain units species. Calorimetric study of the dissolution of glasses in acid solution shows a decrease of the dissolution enthalpy when the SrO is added. © 2016 Elsevier B.V. All rights reserved.

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