Structure, thermal analysis and optical properties of lithium tungsten-titanophosphate glasses (original) (raw)
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Some physical properties of the glasses within the Li 2 O-Li 2 WO 4 -TiO 2 -P 2 O 5 system
Phosphate glasses of the compositions 20Li 2 O-(50-x)Li 2 WO 4-xTiO 2-30P 2 O 5 (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.
Thermal properties and stability of lithium titanophosphate glasses
Journal of Thermal Analysis and Calorimetry, 2009
DTA was used to study thermal properties and thermal stability of (50-x)Li 2 O-xTiO 2 -50P 2 O 5 (x=0-10 mol%) and 45Li 2 O-yTiO 2 -(55-y)P 2 O 5 (y=5-20 mol%) glasses. The addition of TiO 2 to lithium phosphate glasses results in a non-linear increase of glass transition temperature. All prepared glasses crystallize under heating within the temperature range of 400-540°C. The lowest tendency towards crystallization have the glasses with x=7.5 and y=10 mol% TiO 2 . X-ray diffraction analysis showed that major compounds formed by annealing of the glasses were LiPO 3 , Li 4 P 2 O 7 , TiP 2 O 7 and NASICON-type LiTi 2 (PO 4 ) 3 . DTA results also indicated that the maximum of nucleation rate for 45Li 2 O-5TiO 2 -50P 2 O 5 glass is close to the glass transition temperature.
Preparation and characterization of TeO2 –WO3 –Li2O glasses
Glasses in the TeO 2 -WO 3 -Li 2 O system were prepared by using conventional melt-quenching technique. Glass formation range of the system and thermal, physical and structural features of the ternary glasses were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and FTIR analysis according to the equimolar substitution of TeO 2 by WO 3 + Li 2 O and increasing Li 2 O content at constant TeO 2 . Thermal behavior of the glasses was studied in terms of glass transition temperature (T g ), crystallization temperature (T c /T p ) and glass stability against crystallization (ΔT). Density (ρ), molar volume (V M ), oxygen molar volume (V O ), oxygen packing density (OPD), average cross-link density (n c ), Poisson's ratio (μ cal ) and number of bonds per unit volume (n b ) values were calculated for the physical investigation of the glasses. FTIR spectra of the glasses were interpreted in terms of the structural transformations on the glass network by the changing composition.
Study of Tungsten Phosphate Glasses Containing Fe2O3
New Journal of Glass and Ceramics, 2019
Glasses of the compositions 20Li 2 O-(50 − x)Li 2 WO 4-xFe 2 O 3-30P 2 O 5 where (x = 0, 1, 5, 8, 10, 15 mol%) were elaborated by the melt-quenching route. Synthesized glasses are characterized using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), differential scanning calorimetric (DSC), and density determination. The XRD patterns confirmed the amorphous nature of samples, and IR spectra showed the structural groups and highlight the depolymerization of phosphate network with the introduction of iron oxide. It is found that the structural unit Q 2 converts to Q 1 and Q 0 as Fe 2 O 3 replaces Li 2 WO 4. Chemical durability tests on the glasses have shown that the compositions containing pyrophosphate (Q 1) and orthophosphate (Q 0) units are more water-resist. The electrical conductivity measurements were performed by complex impedance spectroscopy in the frequency range of 20-10 6 Hz at various temperatures from ambient to 400˚C. It is found that the conductivity is activated thermally and follows an Arrhenius law. The obtained electrical data were analyzed by the modulus formalism and dielectric formalism. The determined asymmetric nature of max M M ′′ ′′ spectra suggested that the relaxation behavior is non-Debye and characterized by the stretched exponent parameter β < 1.
Journal of Spectroscopy, 2013
New phosphate glasses in the quaternary system (50-x) A 2O-x WO3-10 Nb 2O5-40 P 2O5, with x = 0; 30 and A = Li or Na were prepared by the melt quenching method. e effect on the crystallization behaviour of the glass due to the introduction of WO3 into the glass composition and, consequently, the diminishing of the molar amount of the alkaline oxide and the decreasing of the molar ratio between network modi�ers and network formers (M/F) was studied. e prepared glasses were heat-treated in air, at 550 ○ C, 600 ○ C, and 650 ○ C for 4 hours. e structure, of the obtained samples, was studied by differential thermal analysis (DTA), X-ray powder diffraction (XRD), and Raman spectroscopy and the morphology by scanning electron microscopy (SEM). It was found that the replacement of Li2O or Na2O by WO3 reduces the number of the crystallised phases. In the lithium-niobiophosphate glasses, the presence of WO3 promotes the formation of NbOPO 4 instead of the LiNbO 3 phase and reduces the formation of orthoand pyro-phosphate phases. e thermal treatments affect the arrangements of the network structure of the AW40-glasses.
Study of Tungsten Phosphate Glasses Containing Fe 2 O 3
Glasses of the compositions 20Li 2 O-(50 − x)Li 2 WO 4-xFe 2 O 3-30P 2 O 5 where (x = 0, 1, 5, 8, 10, 15 mol%) were elaborated by the melt-quenching route. Synthesized glasses are characterized using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), differential scanning calorimetric (DSC), and density determination. The XRD patterns confirmed the amorphous nature of samples, and IR spectra showed the structural groups and highlight the depolymerization of phosphate network with the introduction of iron oxide. It is found that the structural unit Q 2 converts to Q 1 and Q 0 as Fe 2 O 3 replaces Li 2 WO 4. Chemical durability tests on the glasses have shown that the compositions containing pyrophosphate (Q 1) and orthophosphate (Q 0) units are more water-resist. The electrical conductivity measurements were performed by complex impedance spectroscopy in the frequency range of 20-10 6 Hz at various temperatures from ambient to 400˚C. It is found that the conductivity is activated thermally and follows an Arrhenius law. The obtained electrical data were analyzed by the modulus formalism and dielectric formalism. The determined asymmetric nature of max M M ′′ ′′ spectra suggested that the relaxation behavior is non-Debye and characterized by the stretched exponent parameter β < 1.
Thermal, structural and optical properties of new tungsten lead–pyrophosphate glasses
Optical Materials, 2011
Crystalline lead–pyrophosphate precursor was prepared in aqueous solution from lead nitrate and phosphoric acid and characterized by X-ray diffraction, thermogravimetry and Raman scattering. This crystalline lead–phosphate was then used to prepare glass samples in the binary system Pb2P2O7–WO3. Dependence of WO3 content on thermal, structural and optical properties were investigated by thermal analysis (DSC), Raman spectroscopy, UV–visible and near-infrared absorption
IARJSET
Sodium aluminophosphate glasses containing lithium ions of composition X Li2CO3-(30-X) Na2 CO3-60 NH6PO4-10Al2O3 (where 20 ≤ x ≥ 5) have been prepared by melt quenching technique. The XRD spectra reveal the presence of no sharp peak confirms that the prepared glass samples were of an amorphous nature. The physical and optical properties of the glasses were investigated with the support of density and molar volume. The density of the glass matrix increases with lithium content and its molar volume shows non-linear variation. The metallic and non-metallic nature of the glass was predicted through the calculation of its physical properties. The optical properties of the prepared glass show mole fraction dependent and are mainly dependent on the basicity and polarizability of the Al2O3 content. The metallization criterion of the glass matrix clearly indicates the size of the conduction and valance band. Optical band gap values were found to decrease from 3.276 to 2.634 eV with aluminium content. The refractive index values were found to increase with lithium content in the glass samples. Inter-nuclear distance, field strength, oxygen packing density, polaron radius, transmission coefficient, reflection loss, dielectric constant and molar refraction were determined to study the physical properties of the glass matrix.
Improvement of thermal and optical properties of lithium phosphate glasses by adding MgO
Journal of Thermal Analysis and Calorimetry, 2017
Collective characterizations of prepared lithium phosphate glass together with samples containing increasing added MgO contents (0-2 mol%) were carried out by differential thermal analysis (DTA), spectroscopic ellipsometry (SE) and photoluminescence (PL) measurements. From the DTA profile, the glass transition temperature T g and crystallization onset temperature T x are estimated. The thermal stability factor was higher than 100°C suggesting that this glass exhibits a good thermal stability and consequently is suitable to be a potential candidate for fiber drawing. Furthermore, the variation of the DT as function of MgO contents has a minimum at 1 mol% of MgO. The refractive index and extinction coefficient data were obtained by analyzing the experimental spectra of tanW and cosD measured by SE. The complex dielectric functions (e = e 1 ? ie 2) of the samples were estimated from regression analysis. Some of the optical absorption parameters, such as high-frequency dielectric constant, e ? , the average values of oscillator strength, S o , wavelength of single oscillator, k o , plasma frequency, x p, and relaxation time, s, have been evaluated. The PL spectra of the MgOdoped glass under 325-nm excitation wavelength were studied. The dependence of PL spectra on doping concentration shows a quenching of the PL intensity for MgO concentration above 1 mol%. The variations of the photoluminescence intensity, thermal stability refractive index and optical constants gave an indication to use the prepared glasses for design of novel functional optical materials with higher optical performance.
The Journal of Physical Chemistry B, 2013
Glasses in the ternary system (70 − x)NaPO 3 -30WO 3 -xBi 2 O 3 , with x = 0−30 mol %, were prepared by the conventional melt-quenching technique. X-ray diffraction (XRD) measurements were performed to confirm the noncrystalline nature of the samples. The influence of the Bi 2 O 3 on the thermal, structural, and optical properties was investigated. Differential scanning calorimetry analysis showed that the glass transition temperature, T g , increases from 405 to 440°C for 0 ≤ x ≤ 15 mol % and decreases to 417°C for x = 30 mol %. The thermal stability against devitrification decreases from 156 to 67°C with the increase of the Bi 2 O 3 content. The structural modifications were studied by Raman scattering, showing a bismuth insertion into the phosphate chains by Bi−O−P linkage. Furthermore, up to 15 mol % of Bi 2 O 3 formation of BiO 6 clusters is observed, associated with Bi−O−Bi linkage, resulting in a progressive break of the linear phosphate chains that leads to orthophosphate Q 0 units. The linear refractive index, n 0 , was measured using the prism-coupler technique at 532, 633, and 1550 nm, whereas the nonlinear (NL) refractive index, n 2 was measured at 1064 nm using the Z-scan technique. Values of 1.58 ≤ n 0 ≤ 1.88, n 2 ≥ 10 −15 cm 2 /W and NL absorption coefficient, α 2 ≤ 0.01 cm/GW, were determined. The linear and NL refractive indices increase with the increase of the Bi 2 O 3 concentration. The large values of n 0 and n 2 , as well as the very small α 2 , indicate that these materials have large potential for all-optical switching applications in the near-infrared.