| 1. |
- Bih, H., et al.
(författare)
-
Pentaammonium heptasodium [bis(μ5-phosphato) pentakis (μ2-oxido)-decaoxidopentamolybdenum(VI)] henicosahydrate
- 2010
-
Ingår i: Acta Crystallographica Section E. - 1600-5368. ; E66, s. 20-21
-
Tidskriftsartikel (refereegranskat)abstract
- The title compound, (NH4)(5)Na-7[Mo5P2O23](2)center dot 21H(2)O, was prepared under atmospheric conditions in aqueous solution at room temperature. The structure contains the [Mo5P2O23](6-) heteropolyoxometallate anion, which has been previously reported a number of times with a variety of differing countercations. Each anion is built up of five MoO6 octahedra sharing an edge and forming a ring which is closed by common corners of the terminal octahedra. The rings are closed on both sides by two asymmetric PO4 tetrahedra, sharing three corners with three MoO6 octahedra. The anions are chiral and the two independent anions in the asymmetric unit were arbitarily chosen with the same chirality, but the centrosymmetric crystal contains both enantiomers. The structure can alternatively be described as a succession of layers parallel to (101), formed by the [Mo5P2O23](6-) anions and linked by sodium chains. Water molecules and ammonium ions fill the remaining space and ensure the cohesion through extensive N-H center dot center dot center dot O and O-H center dot center dot center dot O hydrogen bonding.
|
|
| 2. |
|
|
| 3. |
- Bih, H, et al.
(författare)
-
Thermal and structural studies of Li2O-Na2O-SrO-TiO2-B2O3-P2O5 glasses by DTA, IR and EPR spectroscopy
- 2017
-
Ingår i: Journal of Applied Surfaces and Interfaces. ; 1:1-3, s. 57-63
-
Tidskriftsartikel (refereegranskat)abstract
- Glasses in the system 33.33[xNa2O-(1-x)Li2O]-2.5SrO-2.5TiO2-45B2O3-16.67P2O5 (0.0 ≤ x ≤ 1.0) were prepared by standard melt quenching procedures, and their physical properties were characterized by thermal analysis, density measurements. Their local structures were comprehensively characterized by Infrared spectroscopy (IR) and electron paramagnetic resonance (EPR). The variation of the glass transition temperature as a function of the glass compositions is non-linear. The infrared spectroscopy of the glasses has identified the presence of different structural grouping units in the glassy-matrix. It is found that the stretching and bending vibration modes of borate groups are more sensitive to the substitution of alkali elements. EPR experiments have shown the presence of Ti3+ centres in the glasses. The variation of the g-factor as a function of the Na/(Na+Li) ratio presents a minimum around (x=0.5). The composition non-linearity behavior of Tg, vibration bending mode, and g-factor are signature of the mixed alkali effect in the glasses.
|
|
| 4. |
- Sartelli, Massimo, et al.
(författare)
-
Ten golden rules for optimal antibiotic use in hospital settings: the WARNING call to action
- 2023
-
Ingår i: WORLD JOURNAL OF EMERGENCY SURGERY. - 1749-7922. ; 18:1
-
Forskningsöversikt (refereegranskat)abstract
- Antibiotics are recognized widely for their benefits when used appropriately. However, they are often used inappropriately despite the importance of responsible use within good clinical practice. Effective antibiotic treatment is an essential component of universal healthcare, and it is a global responsibility to ensure appropriate use. Currently, pharmaceutical companies have little incentive to develop new antibiotics due to scientific, regulatory, and financial barriers, further emphasizing the importance of appropriate antibiotic use. To address this issue, the Global Alliance for Infections in Surgery established an international multidisciplinary task force of 295 experts from 115 countries with different backgrounds. The task force developed a position statement called WARNING (Worldwide Antimicrobial Resistance National/International Network Group) aimed at raising awareness of antimicrobial resistance and improving antibiotic prescribing practices worldwide. The statement outlined is 10 axioms, or "golden rules," for the appropriate use of antibiotics that all healthcare workers should consistently adhere in clinical practice.
|
|
| 5. |
|
|
| 6. |
- Azdouz, M, et al.
(författare)
-
Synthesis, Rietveld refinements and Raman spectroscopy studies of the solid solution Na1-xKxPb4(VO4)(3) (0 <= x <= 1)
- 2010
-
Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860 .- 1872-8014. ; 963:2-3, s. 258-266
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study we report the synthesis, crystal structure and Raman spectroscopy studies of Na1-xKxPb4(VO4)(3) orthovanaclates solid solutions (0 <= x <= 1). Rielveld refinements showed that this solid solution is continuous adopting P6(3)/m (no. 176) space group. Some of Pb(II) cations are located in the (6 h) sites. The ninefold coordination sites (4f) are equally occupied by the other lead cations and the K+ and Na+ monovalent ions. The structure can be described as built up from [VO4](3-) tetrahedral and Ph2+ of sixfold coordination cavities (6 h positions), which delimit void hexagonal tunnels running along [0 0 1]. These tunnels are connected by cations of mixed sites (4f) half occupied by Pb(II) and half by Na+/K+ mixed cations. The existence of this type of lacunar apatite seems to be conditioned by the presence of lone pair cations Pb(II). Raman spectra of all the compositions are similar and show some linear shifts in band positions as a function of the composition toward high values due the substitutions of Na+ by K+ with a larger radius. No considerable changes in the temperature dependence of the Raman modes and the corresponding FWHM are observed and thus no temperature induced phase transition is observed in Na0.5K0.5Pb4(VO4)(3) up to 650 K.
|
|
| 7. |
- Bih, H., et al.
(författare)
-
Electrical Transport Properties Of Iodine Oxide Phosphate Glasses Issued From The NaI-Li2O-WO3-P2O5 System
- 2010
-
Ingår i: Moroccan Journal of Condensed Matter. - 1114-2073. ; 12, s. 98-102
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract: This work concerns the investigation of ion transport behaviour of NaI containing lithium tungstenphosphate glasses in order to understand better the role of NaI in the ionic cation transport. Glasses obtained in thesystem 0.5[x(2NaI)-(1-x)Li2O]-0.5[0.25(WO3)2-0.75P2O5] were investigated. The glass samples have beencharacterised using powder X-ray diffraction (XRD), thermal analysis, density and impedance spectroscopy. X-raydiffraction and thermal studies have confirmed that these glasses can be formed in the range x = 0 to 1. The mixedalkali glasses have shown higher activation energies and lower conductivities compared to single alkali doped glassesand this has been attributed to a mixed alkali effect.
|
|
| 8. |
- Bih, H., et al.
(författare)
-
Preparation and electrical conductivity of NaF-Li2O-WO3-P2O5 glasses
- 2009
-
Ingår i: Journal of Optoelectronics and Advanced Materials. - 1454-4164 .- 1841-7132. ; 3:9, s. 959-963
-
Tidskriftsartikel (refereegranskat)abstract
- Several studies have been reported on lithium phosphate glasses to which lithium halides and lithium sulphate have been added However, there has been no experimental results for the introduction of sodium fluoride into the lithium tungsten phosphate network How specifically this feature - mixed alkali in the presence of fluorine ion - influences ion transport in the glasses is unclear. This work concerns the investigation of ion transport behaviour of NaF containing lithium tungsten phosphate glasses in order to understand better the role of NaF in the ionic cation transport Glasses obtained in the system 0.5[x(2NaF)-(1-x)Li2O]-0.5[0.25(WO3)(2)-0.75P(2)O(5)] were investigated The glass samples have been characterised using powder X-ray diffraction (XRD), thermal analysis, density and impedance spectroscopy X-ray diffraction and thermal studies have confirmed that these glasses can be formed in the range x = 0 to 1 The mixed alkali glasses have shown higher activation energies and lower conductivities compared to single alkali doped glasses and this has been attributed to a mixed alkali influence on the electrical conduction in these systems.
|
|
| 9. |
- Bih, H., et al.
(författare)
-
Raman spectroscopic study of the phase transitions sequence in Li3Fe2(PO4)(3) and Na3Fe2(PO4)(3) at high temperature
- 2009
-
Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860 .- 1872-8014. ; 936, s. 147-155
-
Tidskriftsartikel (refereegranskat)abstract
- The phase transition properties of A3Fe2(PO4)3 (A = Li, Na) were studied by Raman spectroscopy. Several Raman bands change continuously in 25–400 °C temperature range, indicating a phase transition from the γ, β to the α-phase occurring at this range of temperature. Bands caused by vibrations of phosphate anion and different ions have been found. The spectra analysis reveals that the modes, located at low frequency range 100–400 cm−1, near 500 cm−1 at room temperature, are the most thermo-sensitive. In addition, the modes corresponding to bond valence stretching of (PO4) unit in the frequency region 970–1200 cm−1 show also evolution with temperature but less sensitive than the above ones. It is observed that phosphate groups show some ordering with temperature. According to our Raman study, we can state that each of the compounds LiFeP and NaFeP shows two reversible phase transformations in the temperature range studied.
|
|
| 10. |
- Bih, H., et al.
(författare)
-
X-ray diffraction and vibrational Raman spectra of the Li2-xNaxCo2(MO4)3 (0
- 2010
-
Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860 .- 1872-8014. ; 965:1-3, s. 7-13
-
Tidskriftsartikel (refereegranskat)abstract
- Synthesis, X-ray diffraction and Raman spectroscopy studies of Li2-xNaxCo2(MoO4) 3 (0 ≤ x ≤ 2) compositions have been investigated. These alkali-cobalt molybdates crystallize in the orthorhombic system (space group Pnma (D2h)) with a lyonsite structure (Z = 4). The cell parameters are determined by DICVOL04 software and confirmed by Rietveld refinements. The structure is formed by a framework of MoO4 tetrahedra and (Li/Na/Co)O6 octahedra, the tetrahedra provide links between sheets and columns formed by the octahedra. The structure shows that while octahedra share corners and edges in the sheets, they share faces columns. Alkali and cobalt are distributed statically in both the octahedral and trigonal prism sites. X-ray diffraction shows the presence of a solid solution in the range of compositions (0 ≤ x < 1.4). These results are in agreement with Raman studies where the spectra of all the compositions are similar and show linear shifts of the frequencies as a function of the composition toward low values due to the substitutions of Li+ by Na+ with a larger radius.
|
|
| 11. |
- Jerroudi, M., et al.
(författare)
-
Elaboration, Thermal and Structural Approach of Manganese Phosphate Glasses Inside the System of K2O-MnO2-P2O5
- 2020
-
Ingår i: International Conference On Advanced Materials, Microscopy And Energy (ICAMME) 2019. - : IOP Publishing.
-
Konferensbidrag (refereegranskat)abstract
- Glasses of the composition (50-x/2) K2O-xMnO(2)-(50-x/2) P2O5 with (0 <= x <= 30%mol), have been prepared by standard melt quenching procedures. The amorphous state of the glasses is evidenced using the X-Ray diffraction. Their physical properties were characterized by thermal analysis and density measurements. The density and the glass transition temperature increase with increasing in MnO2 content. To study the structural role of MnO2 oxide in studied glasses, the FTIR and Raman spectroscopies have been employed. It was highlighted that the presence of MnO2 allows the depolymerisation of the phosphate chains and formation of covalent bonds P-O-Mn, which replace P-O-P and P=O linkages.
|
|
| 12. |
- Jerroudi, M., et al.
(författare)
-
ESR, physical and structural studies on Mn2+ doped in mixed alkali phosphate glasses
- 2021
-
Ingår i: Materials Today. - : Royal Society of Chemistry. - 2214-7853. ; 37, s. 3876-3881
-
Tidskriftsartikel (refereegranskat)abstract
- Glass formation and properties of manganese phosphate glasses containing both Na2O and K2O oxides with the general formula 49.95[xNa2O-(1-x)K2O]-0.1MnO2-49.95P2O5 with x = 0–1 mol%, have been investigated. The vitreous samples were prepared by standard melt quenching. To get an insight into their physical properties, the density and the glass transition temperature were procedure determined. The structure of the glass was performed by Infrared, Raman, and electron spin resonance (EPR) spectroscopies. The results obtained by these techniques have allowed us to explain their structure and properties upon the variation of the chemical composition. The variation of the glass transition temperature as a function of the composition presents a minimum for the ratio Na/Na + K = 0.5. Infrared and Raman spectroscopies has identified the presence of different structural grouping units in the glassy-network. It is found that the stretching vibration νs(PO2)− and νs(P–O–P) are more sensitive to the substitution of alkali elements. EPR experiments have shown the presence of Mn2+ centers in the glasses. The variation of the g-factor as a function of the composition is non-linear. The non-linearity behavior of the composition dependence of Tg, vibration bending mode, and the g-factor are a fingerprint of the mixed alkali effect in the glasses under study.
|
|
| 13. |
- Jerroudi, M., et al.
(författare)
-
Optical and electrical properties of manganese doped-alkali metaphosphate glasses
- 2020
-
Ingår i: Materials today. - : Elsevier BV. - 2214-7853. ; , s. 1052-1055
-
Konferensbidrag (refereegranskat)abstract
- Phosphate glasses are of large interest for a variety of technological applications due to their several unique properties. In this work we investigate structural, optical and electrical properties of some alkali metaphosphate glasses doped with manganese oxide inside the system (50-x/2) K2O-xMnO(2)-(50-x/2) P2O5 with (0 <= x <= 30%mol). The glassy samples have been prepared using a melt-quench process. The obtained glasses are colored and the valence of manganese is composition dependence. The local structure of Mn2+ in the glasses is evaluated by EPR spectroscopy. The optical absorption spectra have been used to evaluate the values of the optical band gap (E-g) and Urbach energy (Delta E). The variation of these optical parameters as a function of composition is investigated. The presence of Mn3+ in the glasses is established by the optical absorption and this ion is associated with the absorption band at 520-530 nm. dc conductivity of the glasses is studied and it is found that it is thermally activated and followed an Arrhenius behavior.
|
|
| 14. |
- Jerroudi, M., et al.
(författare)
-
Thermal, optical and electrical properties of MnO2-doped mixed sodium potassium phosphate glasses
- 2021
-
Ingår i: Journal of thermal analysis and calorimetry (Print). - : Springer Nature. - 1388-6150 .- 1588-2926. ; 146, s. 1077-1090
-
Tidskriftsartikel (refereegranskat)abstract
- Glasses in the system (1 - x)(0.5NaPO(3)-0.5KPO(3))-xMnO(2), with 0 <= x <= 50 mol%, have been prepared using a melt-quench route. The glasses exhibit a yellow to dark color with the increase in manganese content owing to the presence of Mn(2+)and Mn(3+)ions in the network. The amorphous state of the glasses is evidenced by the X-ray diffraction. In order to get an insight into the physical and structural aspects of these vitreous materials, we have determined some of their parameters such as density, molar volume and glass transition temperature. From differential thermal analysis scan on heating, we evaluated the glass transition temperature (T-g) of each glass, which corresponds to the phase transition temperature from solid to viscous liquid. The density (rho) as a structural index is found to increase while the corresponding molar volume decreases with MnO(2)content. The structural approach of the studied glasses is evaluated by infrared (IR) and electron paramagnetic resonance (EPR) spectroscopies. IR technique allowed us to identify the coexisting bond vibration modes in the glass network, and it has shown that many structural phosphates units coexist, mainly pyrophosphate and metaphosphate structural groups. EPR experiments have shown the presence of Mn(2+)centers in the glasses. The UV-Visible absorption is utilized to estimate the values of the optical band gap (E-g) and Urbach energy (Delta E). The optical band gap energy is determined from both the absorption spectrum fitting (ASF) and Tauc's methods. These optical parameters are composition dependence. The dc conductivity of the glasses is determined in the temperature range from 303 to 473 K. It decreases with increasing manganese content. It is thermally activated and followed an Arrhenius behavior. The crystallization of glasses is realized by submitting them to heat treatments, and the crystallized phases are identified by XRD analysis. The crystallization kinetic was studied under non-isothermal conditions. The activation energy (E-c) and the Avrami parameter (n) were determined.
|
|
| 15. |
- Manoun, B., et al.
(författare)
-
High temperature and composition induced phase transitions in LiZnV1-xAsxO4 phenacites : Crystal structure and Raman spectroscopy studies
- 2015
-
Ingår i: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - : Elsevier BV. - 1386-1425 .- 1873-3557. ; 151, s. 956-964
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, using techniques of X-ray diffraction and Raman spectroscopy, we report the composition and high-temperature induced phase transition in the system LiZnV1-xAsxO4 (0 <= x <= 1). Both techniques showed that the increase of arsenic amount induced a structural transition from R-3 LiZnVO4 type to LiZnAsO4 type belonging to R3 space group, the transition occurring between x = 0.7 and x = 0.8. Furthermore, increasing temperature for the compositions (0.8 <= x <= 1) manifests a transition from the LiZnAsO4 structural type with R3 space group to the R-3 LiZnVO4 structural type. For this series, the transition from the space group R3 to the centro-symmetric space group R-3 shows considerable changes in the compositional and temperature dependencies of the bands: spectral positions of all the observed Raman bands exhibit shifts linearly proportional to the temperature increase, with points of shift-rate changes revealing a symmetry change. The Raman-spectra based temperature-composition phase diagram confirms the results obtained using the method of Rietveld refinements, thus showing the R-3 to R3 transition occurring between x = 0.7 and 0.8.
|
|
| 16. |
- Azdouz, M., et al.
(författare)
-
Crystal chemistry, Rietveld refinements and Raman spectroscopy studies of the new solid solution series: Ba3−xSrx(VO4)2 (0≤x≤3)
- 2010
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 498:1, s. 42-51
-
Tidskriftsartikel (refereegranskat)abstract
- The new solid solution series Ba3-xSrx(VO4)(2) (0 <= x <= 3) has been synthesized and studied by a combination of X-ray powder diffraction and Raman vibrational spectroscopy. This continuous solid solution crystallise in the hexagonal system with R (3) over barm space group. The structure has been determined at room temperature from X-ray diffraction by the Rietveld method analysis. It is formed by a 3D network of (Ba/Sr)((1))(VO4)(2)(4-) layers linked into a crystal network by (Ba/Sr)(2+)((2)) cations. The vibrational spectra of this crystalline orthovanadate solid solution series are interpreted by means of factor group analysis in terms of space group R (3) over barm (D-3d(5)). Assignments of the V-O vibrational stretching and bending modes, as well as some of the external modes, have been made. While all the modes show a monotonous shift as a function of the composition x, a break in the curves of intensities, full width at half maximum and band areas as a function of x is observed and attributed to the statistical distribution of Ba and Sr ions in the same crystallographic sites.
|
|
| 17. |
|
|
| 18. |
- Bensaid, H., et al.
(författare)
-
New molybdate Li2Co2xNix(MoO 4) 3 (0≤x≤2) materials with a lyonsite structure: X-ray diffraction and Raman spectroscopy studies
- 2013
-
Ingår i: Journal of Molecular Structure. - : Elsevier. - 0022-2860 .- 1872-8014. ; 1031, s. 152-159
-
Tidskriftsartikel (refereegranskat)abstract
- A solid solution was found to exist in the quaternary Li2O–CoO–NiO–MoO3 system between the two phases Li2Co2(MoO4)3 and Li2Ni2(MoO4)3. Both Li2Co2(MoO4)3 and Li2Ni2(MoO4)3 are isostructural with the mineral lyonsite, and substitution according to the formula Li2Co2−xNix(MoO4)3 (0 ⩽ x ⩽ 2) demonstrates that a complete solid solution exits. Rietveld analysis revealed that solid solution crystallizes at room temperature in orthorhombic space group Pnma (D2h). The structure shows that if the corners and edges octahedra share in the leaves, they share faces columns. Nickel and cobalt are shared statically in the trigonal prism and octahedral sites. The results of these compositions are consistent with studies where the Raman spectra. Therefore, all compositions are similar and show linear changes frequencies depending on the composition due to the substitution of Co2+ by Ni2+ with a larger radius.
|
|
| 19. |
- Bensaid, H., et al.
(författare)
-
X-ray structure refinement of solid solution Ba2.15-xNa0.7+xNb5-xWxO15 and the investigation of the orthorhombic-tetragonal phase transition by Raman spectroscopy
- 2011
-
Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860 .- 1872-8014. ; 988:1-3, s. 136-143
-
Tidskriftsartikel (refereegranskat)abstract
- Crystal structures of Ba2.15-xNa0.7+xNb5-xWxO15 (BaNaNbW) materials were investigated by X-ray diffraction and refined using the Rietveld method. It is shown that all the samples crystallize in the tungsten tetragonal bronze (TTB) like structure and form a solid solution in the range (0 ≤ x ≤ 1). To study the temperature induced phase transition in these compounds, Raman spectra were collected in situ at room pressure and elevated temperatures, up to 330°. The Raman results show strong evidence that the materials under study go through a phase transition around Te = 270 °C. The value of the transition temperature depends on the chemical composition and increases with increasing tungsten content in the materials at a linear rate. The observation of this phase transition by Raman technique is in agreement with dielectric spectroscopy anomaly.
|
|
| 20. |
- El Hachmi, A., et al.
(författare)
-
Structural and Mössbauer Studies of Sr(1.5)Ca(1.5)Fe(2.25)Mo(0.75)O(9-delta)and Sr(1.92)Ca(1.08)Fe(2.04)W(9-delta)Double Perovskites
- 2020
-
Ingår i: Journal of Structural Chemistry. - : Pleiades Publishing Ltd. - 0022-4766 .- 1573-8779. ; 61:6, s. 861-872
-
Tidskriftsartikel (refereegranskat)abstract
- Sr(1.50)Ca(1.50)Fe(2.25)Mo(0.75)O(9-delta)and Sr(1.92)Ca(1.08)Fe(1.04)W(0.96)O(9-delta)double perovskites are synthesized in the polycrystalline form by a solid-state reaction route in air and studied at room temperature using the of PXRD, Raman and Mossbauer spectroscopy techniques. The Rietveld refinement analysis reveals that both compounds adopt a tetragonal system with the space groupI4/m and lattice parametersa=b= 5.5176(1) A andc= 7.8065(2) A for Sr(1.50)Ca(1.50)Fe(2.25)Mo(0.75)O(9-delta)anda=b= 5.5453(1) A andc= 7.8388(1) A for Sr1.92Ca1.08Fe2.04W0.96O9-delta. Raman spectra are consistent with the group theoretical analysis predicted for tetragonal symmetryI4/m(point group C4h5).Fe-57 Mossbauer spectra recorded at room temperature show a paramagnetic behavior for Sr1.50Ca1.50Fe2.25Mo0.75O9-delta, and magnetic ordering for Sr1.92Ca1.08Fe2.04W0.96O9-delta. The isomer shift (delta) and quadrupole splitting (Delta) values are characteristic of high-spin Fe(3+)in a distorted octahedral coordination.
|
|
| 21. |
- El Hachmi, A., et al.
(författare)
-
Structural, Magnetic and Optical Properties Study of Tellurium-Based Perovskites : Sr3-xPbxFe2TeO9 (0 <= x <= 2.25)
- 2020
-
Ingår i: JOURNAL OF INORGANIC AND ORGANOMETALLIC POLYMERS AND MATERIALS. - : Springer Science and Business Media LLC. - 1574-1443 .- 1574-1451. ; 30:6, s. 1990-2006
-
Tidskriftsartikel (refereegranskat)abstract
- Polycrystalline samples of the series of triple perovskites Sr3-xPbxFe2TeO9 (0 <= x <= 2.25) (SPFTO) were synthesized using solid state reaction. These materials have been studied by a combination of X-ray powder diffraction (XRPD), Mossbauer spectrometry, Raman and UV-Vis spectroscopies. The crystal structures were resolved by the Rietveld refinement method, and revealed that this Sr3-xPbxFe2TeO9 (0 <= x <= 2.25) system shows one space group change from tetragonal I4/m (0 <= x <= 1) to another tetragonal form I4/mmm (1.25 <= x <= 1.88) and a second transition to hexagonal R3 over bar m (2.08 <= x <= 2.25). An anti-site disordering of Fe and Te on the B sites has been detected indicating the presence of a partial amount of Te at Fe positions and vice versa. The valence state of iron in the Fe site was determined to be Fe(III) by Mossbauer spectrometry, which also revealed two sites in a concordance with the XRPD measurements. Fe-57 Mossbauer spectra measurements show paramagnetic and magnetic ordering behaviors. The observed Raman spectra as a function of composition show obvious changes on the positions (wavenumbers), the FWHM and the intensities of the modes confirming the phase transformations observed by the XRPD results. These structural transitions led to a distinct change in the optical band gap energy, varying from 2.14 to 1.85 eV.
|
|
| 22. |
- El Hachmi, Abdelhadi, et al.
(författare)
-
Synthesis and Rietveld refinements of new ceramics Sr2CaFe2WO9 and Sr2PbFe2TeO9 perovskites
- 2018
-
Ingår i: Powder Diffraction. - : J C P D S-INT CENTRE DIFFRACTION DATA. - 0885-7156 .- 1945-7413. ; 33:2, s. 134-140
-
Tidskriftsartikel (refereegranskat)abstract
- Ceramics of Sr2CaFe2WO9 and Sr2PbFe2TeO9 double perovskites have been prepared in polycrystalline form by solid-state technique, in the air. The crystalline structure was analyzed using X-ray powder diffraction (XRPD) at room temperature. Rietveld analysis of XRPD) patterns show that both compounds adopt a tetragonal structure with space group I4/m, with unit cell parameters a = 5.5453(1) angstrom, c = 7.8389(1) angstrom for Sr(2)CaFc(2)WO(9), and a = 5.5994(15) angstrom, c = 7.8979(30) angstrom for Sr2PbFe2TeO9. A certain degree of anti-site disordering of W and/or Te and Fe on the B -sites have been detected, indicating the presence of a partial amount of W and/or Te at Fe positions and vice versa.
|
|
| 23. |
- Es-Soufi, H., et al.
(författare)
-
Some physical properties of the glasses within the Li2O-Li2WO4-TiO2-P2O5 system
- 2016
-
Ingår i: Dielectric Materials And Applications, ISYDMA '2016. - : MATERIALS RESEARCH FORUM LLC. - 9781945291180 ; , s. 266-269
-
Konferensbidrag (refereegranskat)abstract
- Phosphate glasses of the compositions 20Li(2)O-(50-x)Li2WO4-xTiO(2)-30P(2)O(3) (0 <= x <= 15, mol%) were prepared by the melt quenching method. The amorphous nature of these glasses was confirmed by the XRD diffraction. Their characteristic temperatures were determined by DSC analysis. Impedance spectroscopy is used to determine their electrical conductivity as a function of temperature. The obtained results show that the conductivity as a function of temperature follows an Arrhenius-law.
|
|
| 24. |
- Es-Soufi, H., et al.
(författare)
-
Structure, thermal analysis and optical properties of lithium tungsten-titanophosphate glasses
- 2017
-
Ingår i: Journal of Non-Crystalline Solids. - : Elsevier. - 0022-3093 .- 1873-4812. ; 463, s. 12-18
-
Tidskriftsartikel (refereegranskat)abstract
- A melt-quenching method is used to prepare homogeneous glasses inside the 20Li(2)O-(50-x)Li2WO4-xTiO(2)-30P(2)O(5) (x = 0, 5, 8,10 and 15 mol%) system. The amorphous and glassy states of the glasses are evidenced by the X-ray diffraction and differential scanning calorimetry (DSC) analysis, respectively. The glasses were found to be colorless. The determined parameters for the glasses such as density, molar volume and glass transition temperature (T-g) depend strongly on the chemical composition of the glasses. The density and T-g are found to decrease and increase with TiO2 content, respectively. Infrared (IR) spectroscopy is used to characterize their structural approach. This technique has allowed the identification of different phosphate structural units mainly pyrophosphate and metaphosphate in their structure. From the absorption edge studies, the values of the optical band gap, E-g, and Lirbach energy, Delta E, were evaluated. The optical band gap is found to depend on the glass composition and it decreases as the content of the TiO2 increases. (C) 2017 Elsevier B.V. All rights reserved.
|
|
| 25. |
|
|
