Structural study of BaO-MoO3-P2O5 glasses by Raman and NMR spectroscopy (original) (raw)
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Structural study of PbO–MoO3–P2O5 glasses by Raman and NMR spectroscopy
Journal of Non-Crystalline Solids, 2011
Glasses in the ternary system PbO-MoO 3 -P 2 O 5 were prepared in three compositional series (100 − x) [0.5PbO-0.5P 2 O 5 ]-xMoO 3 (A), 50PbO-yMoO 3 -(50 − y)P 2 O 5 (B) and (50 − z)PbO-xMoO 3 -50P 2 O 5 (C) and their structure was studied by Raman and 31 P NMR spectroscopies. In the compositional series (100 − x) [0.5PbO-0.5P 2 O 5 ]-xMoO 3 homogeneous glasses were prepared in the concentration region of 0-70 mol% MoO 3 . Their glass transition temperature increases with increasing MoO 3 content having a maximum at x = 50 mol% MoO 3 . 31 P MAS NMR spectra reveal that in the glass series (A) the incorporation of MoO 3 results in the shortening of phosphate chains and gradual transformation Q 2 units into Q 2 and Q 0 units, prevailing in glasses with a high MoO 3 content. Octahedral structural units MoO 6 dominate in most glass compositions and they are present also in the structure of Pb(MoO 2 ) 2 (PO 4 ) 2 compound corresponding to the glass composition 50Pb(PO 3 ) 2 -50MoO 3 . The analysis of Raman spectra of glasses of the (B) series with a high MoO 3 content showed the transformation of octahedral MoO 6 units into tetrahedral MoO 4 units.
Molybdenum modified phosphate glasses studied by 31P MAS NMR and Raman spectroscopy
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015
h i g h l i g h t s Glasses from the P 2 O 5 ASiO 2 AK 2 OACaOAMgOAMoO 3 system were analysed. The modifier role of MoO 3 was confirmed via 31 P MAS NMR and Raman spectroscopy. The introduction of MoO 3 results in depolymerisation of the phosphate framework. It was shown that molybdate units can form [MoO 4 /MoO 6 ]AOAP or [MoO 4 /MoO 6 ]AOASi bonds. The molybdate units can form bonds with NBOs atoms of Q 2 methaphosphate units.
The modifier/former role of MoO3 in some calcium-phosphate glasses
Journal of Alloys and Compounds, 2013
This paper report the results obtained by EPR and Raman investigations of xMoO 3 Á(100 À x)[P 2 O 5 ÁCaO] with 0 6 x 6 50 mol% glass system. From EPR spectroscopy were evidenced the local symmetry and the interaction between Mo 5+ ions. Depending on the content of MoO 3 were highlighted the EPR spectra modifications. By Raman spectroscopy were identified and analyzed the modification which appear on the characteristic bands of these glasses. At low concentration of molybdenum oxide the specific Raman bands of long phosphate chains (Q 2 ) dominate the spectra meanwhile for high molybdenum content the most intense bands are those specific to MoO 3 and short phosphate groups. From both techniques we can conclude that at low concentration of molybdenum oxide, it acts as a very strong network modifier while for high concentrations it plays the role of network co-former.
MoO3 as a structure modifier of glasses from P2O5–SiO2–K2O–MgO–CaO system
Materials Letters, 2014
Infrared spectroscopy and density are advantageous tools for the investigations of glasses and they have been used to obtain information concerning the local structure of phosphate-silicate glasses from P 2 O 5-SiO 2-K 2 O-MgO-CaO system modified with the addition of MoO 3. It has been found that MoO 3 plays the network modifier role in the studied glasses which follows from the gradual breakage of oxygen bridges, i.e. P-O-P, Si-O-Si and/or Si-O-P, and the following formation of connections such as Mo[MoO 4 ]-O-Si and/or Mo[MoO 4 ]-O-P. In summary, it is concluded that the increase of MoO 3 content in the structure of glasses of P 2 O 5-SiO 2-K 2 O-MgO-CaO system results in weakening of the structure, resulting in their frameworks depolymerisation.
Glass-forming ability and structure of ZnO–MoO3–P2O5 glasses
Journal of Non-Crystalline Solids, 2010
Glasses in the ternary system ZnO-MoO 3 -P 2 O 5 were studied. The determined glass-forming region is very large and covers the concentration range from pure P 2 O 5 up to the glass compositions with only 20 mol% P 2 O 5 and 70 mol% MoO 3 . Structure of these glasses was analyzed in four compositional series containing 50 mol% of P 2 O 5 in the series of (50 − t)ZnO-tMoO 3 -50P 2 O 5 , 10 mol% of ZnO in the series of 10ZnO-yMoO 3 -(90 − y)P 2 O 5 and 20 mol% MoO 3 in the series of zZnO-20MoO 3 -(80 − z)P 2 O 5 . The fourth series contained equimolar ratio of ZnO/P 2 O 5 and its composition was (100 − x)[0.5ZnO-0.5P 2 O 5 ]-xMoO 3 . Basic structural units in this ternary system were identified in specific compositional regions using Raman and 31 P MAS NMR spectroscopy. By the deconvolution of NMR spectra compositional dependences of Q n units were obtained. The presence of isolated MoO 6 octahedra was detected in the glass with 70 mol% P 2 O 5 . In the MoO 3 -rich and ZnO-rich region clustering of MoO 6 octahedra was observed, but the formation of Mo-O-Mo bonds was found already in the P 2 O 5 -rich glasses containing 60 mol% P 2 O 5 . Molybdate structural units are preferentially bonded to non-bridging oxygen atoms of PO 4 units and P-O-Mo bonds do not tend to replace P-O-P bonds.
Journal of Non-Crystalline Solids, 2011
In this study, the disordered network of calcium phosphate glasses is investigated by Raman scattering and 31 P magic angle spinning (MAS) solid-state NMR spectroscopies. The use of both spectroscopies in a combined approach allows drawing a detailed understanding of the structure of these glasses. The P-O-P connectivity between successive PO 4 tetrahedra is probed using through-bond double quantum-single quantum (DQ-SQ) and triple quantum-single quantum (TQ-SQ) MAS NMR correlation experiments. Over the broad range of glass compositions studied here, two very different phosphate network topologies are encountered. The results obtained for the polyphosphate compositional range (above 50 mol% Ca) allow determining the phosphate chain-length distribution in the glass as a function of the modifier cation content. For the ultraphosphate region (below 50 mol% Ca), the network topology undergoes a sudden change close to 39 mol% Ca which can be interpreted in terms of a rigidity transition.
Role of manganese in 20K2O-xMnO-(80-x)P2O5 phosphate glasses and model of structural units
2016
Glasses with composition 20K2O-xMnO-(80-x)P2O5 with 0≤ x ≤30 mol% were prepared by conventional melt quenching technique at 1100°C mixtures of K2CO3, MnCO3 and NH4H2PO4. Their density, molar volume, glass transition temperature and infrared spectroscopy have been investigated. Differential Scanning Calorimetry (DSC) measurements give the variation of glass transition temperature (Tg) from 225°C for x=0 to 440°C for x=30 mol %. The density () measurements increase from 2.28 to 2.89 g.cm -3 . The evolution of infrared spectra with the composition is studied and the oxide forming character is discussed. When manganese oxide is added to potassium phosphate glass, phosphate chains are depolymerized by the incorporation of distorted (4) units through P-O-Mn bonds. it is assumed to be presented as [MnO4/2] 2structural units a corner sharing geometry and the electrical neutrality in the system is achieved by the conversion of [POO3/2] into [PO4/2] + units.
Network structure of molybdenum lead phosphate glasses: Infrared spectra and constants of elasticity
Physica B: Condensed Matter, 2011
Molybdenum lead phosphate glasses doped with La 2 O 3 of the system xMoO 3 -5La 2 O 3 -50P 2 O 5 -(45 À x)PbO, with 0 r x r25 mol%, have been synthesized and studied by FTIR, ultrasonic and differential scanning calorimetry (DSC) in order to investigate the role of MoO 3 content on their atomic structure. The constants of elasticity and Debye temperatures of the glasses have been investigated using sound velocity measurements at 4 MHz. According to the IR analysis, the vibrations of the phosphate structural units are shifted towards higher wavenumbers associated with the formation of bridging oxygens. The change in density with MoO 3 content reveals that the molybdate units are less dense than the lead units. The observed compositional dependence of the constants of elasticity is interpreted in terms of the effect of MoO 3 on the different phosphate bonds. It is assumed that MoO 3 plays the role of a former by increasing the ultrasonic velocity and the constants of elasticity of the phosphate glasses.
FTIR Spectra and Optical Properties of Molybdenum Phosphate Glasses
Glasses in the system 5Na 2 O-5ZnO-5Al 2 O 3-65P 2 O 5-xMoO 3-(20-x)CaO, mol%; where x= 0, 2, 5, 7, 10, 12, 15, 20, have been prepared using the conventional melting and annealing method. Density and molar volume of these glasses were measured. Density was found to increase monotonically with increasing x (i.e. molybdenum oxide content) and, conversely, the molar volume decreased with increasing x. UV-visible optical absorption spectra of the prepared glasses were measured from 190 to 1100 nm. These spectra exhibit charge transfer bands due to iron trace impurities which eventually affect the induced absorption due to MoO 3 and that due to the host base glass in the UV-region. The UV-absorption edge, both direct and indirect allowed transitions with their optical energy gaps, has been studied. Also, the Urbach energy was evaluated. The refractive index and the extinction coefficient data were used to evaluate the absorption coefficient of the different glass compositions. The molar refraction, electronic polarizability and the optical basicity were obtained using the evaluated glass refractive indices. Fourier transform infrared (FTIR) spectra of the investigated glasses have been studied in order to understand the characteristic frequencies of the vibrational chemical bonds which are liable to the structural and spectral changes. These spectra showed IR absorption bands related to the characteristic phosphate and molybdate bonds especially P=O,