Crystallization and microstructure of Eu3 +-doped lithium aluminophosphate glass (original) (raw)
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Journal of Materials Science, 2014
The crystallization kinetics and phase transformation of a transparent Tb 3?-doped lithium-aluminum phosphate glass, prepared by melt quenching, were investigated. The energy associated to the glass transition and the crystallization parameters (activation energy for crystallization and Avrami exponent) were evaluated by different methods using the experimental data obtained by differential thermal analysis performed at different heating rates. Using an isoconversional method to determine the change of the activation energy for crystallization with the fraction of crystallization, it was verified that with the increase in the fraction of crystallization from 0.1 to 0.9, the value of the activation energy decreased slightly from *370 to *310 kJ mol-1 and that the Avrami exponent varied from 0.8 to 1, suggesting a surface crystal growth mechanism. Observation of the microstructural evolution of heat-treated glass samples confirmed a surface crystallization process revealing spherulitic crystals constituted mainly by aluminum metaphosphate.
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.
Science of Sintering
Crystallization kinetics of 22.5Li 2 O•10Al 2 O 3 •30GeO 2 •37.5P 2 O 5 (mol%) glass was studied under non-isothermal condition using the differential thermal analysis (DTA). The study was performed by using the first crystallization peak temperature (T p1) which belongs to the precipitation of LiGe 2 (PO 4) 3 phase in the glass. The activation energy of glass crystallization (E a) was determined using different isokinetic methods. The dependence of E a on the degree of glass-crystal transformation (α) was studied using model-free isoconversional linear integral KAS (Kissinger-Akahira-Sunose) and FWO (Flynn-Wall-Ozawa) methods. It was shown that the E a varies with α and hence with temperature and consequently the glass/crystal transformation can be described as a complex process involving different mechanisms of nucleation and growth.
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.
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 thermophysical properties of primary phase in lithium germanium phosphate glass
Science of Sintering, 2021
The selected lithium germanium-phosphate glass was prepared by a conventional melt-quenching technique. The XRD method was employed to confirm the glass was obtained and to reveal crystalline phases during heat treatment. The dilatometry (DIL), differential thermal analysis (DTA), and differential scanning calorimetry (DSC) were used to determine the characteristic temperatures and enthalpies of crystallization and melting of the crystalline phase. The DTA and DIL were used to obtain the viscosity curves by applying the Vogel-Fulcher-Tammann (VFT) equation
Structure, thermal analysis and optical properties of lithium tungsten-titanophosphate glasses
A melt-quenching method is used to prepare homogeneous glasses inside the 20Li 2 O-(50-x)Li 2 WO 4-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 TiO 2 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 Urbach energy, ΔE, were evaluated. The optical band gap is found to depend on the glass composition and it decreases as the content of the TiO 2 increases.
Journal of Materials Science, 1992
The nucleation and crystallization processes of Li20-AI203-SiO 2 glass-ceramics were investigated by differential thermal analysis. The crystalline phases produced during thermal treatment at different temperatures and the residual glassy phase were characterized by X-ray diffraction, SEM and image analysis techniques. The activation energy of the crystallization process was calculated as E= 380 4-20 kJ mo1-1. The influence of nucleating agents (Ti02, Zr02) was evaluated to obtain glass-ceramics transparent to visible light. The stability of the glassy phase in cooling was determined by means of temperature-time-transformation curves.
Thermal, mechanical and electrical properties of lithium phosphate glasses doped with copper oxide
Bulletin of Materials Science , 2019
Lithium phosphate glasses with the basic composition (P 2 O 5 50 and Li 2 O 50 mol%) series by the addition of copper oxide (0, 10, 15 and 20 g/100 g) were prepared by a melt quenching technique. Fourier-transform infrared (FTIR) absorption spectra and X-ray diffraction (XRD) analysis were used to characterize the glass samples. Thermal expansion and mass density were also measured. The different mechanical properties of the prepared glasses were measured by an ultrasonic non-destructive technique. Additionally, both frequency and temperature dependence of alternating-current conductivity were measured in the frequency range of 40 Hz-1 MHz and the temperature range of 308-488 K. Moreover, direct current conductivity was also measured for the same temperature range. FTIR measurements confirm the appearance of the bands of phosphate groups and the assumption of bonds formed between Cu and P. XRD spectra approve the amorphous nature of the studied glasses. Thermal expansion and mass density of the prepared samples show an increase in values by increasing the CuO content. The mechanical properties of the studied glasses (hardness (H v), Young's modulus (E), elastic modulus (L), bulk modulus (K), shear modulus (G) and Poisson's ratio (ν)) were positively affected by the CuO content, reflecting a better packed structure. Furthermore, the electrical conductivity values of the prepared glasses are identified to increase with an increase in both temperature and CuO content. Such trends agree with the data obtained by thermal expansion and FTIR. The progressive addition of CuO is assumed to improve thermal, mechanical and electrical properties of the prepared lithium phosphate glasses.
Structure and crystallization kinetics of Li2O modified sodium-phosphate glasses
Journal of Molecular Structure, 2015
h i g h l i g h t s Density of glasses depends on the field strength of various cations. 15 mol% Li 2 O contained glass shows higher thermodynamic and kinetic stability. FTIR and Raman study confirmed the higher polymerization in 15 mol% Li 2 O glass. As Li 2 O increases phosphate structural units changes from Q 3 ? Q 2 ? Q 1 ? Q 0 .