Lithium Zinc Silicate Research Articles

Simulation of the impact of Bi2O3 on the performance of gamma-ray protection for lithium zinc silicate glasses

In order to enhance the radiation shielding properties for the lithium zinc silicate glasses and become suitable for gamma-ray protection applications, a partial replacement for the silicon oxide by bismuth oxide was performed. The Monte Carlo (MC) simulation was applied to evaluate the shielding capacity of the investigated glasses. The results recorded by the MC code showed that the replacement of the SiO2 by Bi2O3 causes a significant increase in the investigated glasses shielding capacity. It is varied from 46.732% to 104.207% for the samples containing 20 and 40 mol% of Bi2O3 concentrations compared to the sample containing only 10 mol% of the Bi2O3 at low gamma-photon energy of 0.224 MeV. Moreover, the highest µ values in the present study were received by the glass sample containing 40 mo% of Bi2O3 where the µ varied between 2.700 and 0.216 cm−1 when the applied gamma photon energy increased from 0.244 to 2.506 MeV.

Preparation and electrical properties of LISICON-type lithium zinc silicate from aqueous solution

Preparation and electrical properties of LISICON-type lithium zinc silicate from aqueous solution

Thermo-magnetic properties of Fe2O3-doped lithium zinc silicate glass-ceramics for magnetic applications

The crystallization behaviour and thermo-magnetic characteristics of glass-ceramic based on the 15Li2O–20ZnO–10CaO–55SiO2 system doped with varied Fe2O3 additions (0.0125, 0.025, and 0.05 mol) are described in this work. In some cases, Al2O3 was also added to the iron-containing sample. Glasses were successfully prepared by melt-quenching technique and converted into glass-ceramics by controlled heat-treatment, using DTA, SEM, XRD, and VSM techniques. The density, thermal expansion coefficients (TCE), and magnetic characteristics of the glass-ceramic were examined. XRD results confirmed characteristic peaks for various phases like quartz, Li2ZnSiO4, wollastonite, Li2Si2O5, ZnFe2O4, and β-spodumene. By doping Fe2O3 and Al2O3 with lowering annealing temperature, the particle size was reduce, resulting in glass-ceramics with a more uniform and dense microstructure. The density of glass-ceramics rises from 2.74 g/cm3 to 3.45 g/cm3, whereas the TCE values in average 14–78 × 10−7/°C with temperature range of 25–500 °C. The doped glass-ceramics have superior magnetic properties with saturation magnetization (0.143–0.548 emu/g), the coercivity force (65.116–86.359 G), and remanence magnetization (0.074–0.436 emu/g). Under an alternating magnetic field, the presence of the Zn-ferrite phase in the glass-ceramics improves their magnetic properties and increases their heat-generating capability. Certain features of the doped glass-ceramics control the extensive variety of possibilities for their usage in various magnetic applications particularly for cancer hyperthermia treatment.

Effect of CeO2 addition on crystallization and thermophysical properties of Li2O-ZnO-SiO2 glass-ceramics

The effect of CeO2 addition on crystallization and thermo-physical properties of lithium zinc silicate (LZS) glasses containingLi2O-ZnO-SiO2-Al2O3-Na2O-P2O5 was investigated. The changes of CeO2 contents (2-8 wt.%) had an obvious influence on thetransition temperatures (Tg) and crystallization temperatures (Tc) of LZS glass-ceramics, and they increased with CeO2 contentincreasing. According to XRD analysis, CeO2 promoted the formation of cristobalite and β-spodumene crystals, and β-spodumene increased obviously. As the CeO2 content increasing, the microstructure and microhardness (being 6.88 Gpa at 880oC) of glass-ceramics had great changes. The average thermal expansion coefficient (20 - 450 oC) showed first increasing thendecreasing, having a wide range. The maximum of thermal expansion coefficient was obtained when the glass-ceramicscontained 4 wt.% CeO2, being 175×10−7 K−1 (at 700 oC) and 178×10−7 K−1 (at 880 oC) respectively. Excellent thermo-physicalproperties indicate the glass has greater potential application, such as being used as sealing glass.

A Computational Study of Defects, Li-Ion Migration and Dopants in Li2ZnSiO4 Polymorphs

Lithium zinc silicate, Li2ZnSiO4, is a promising ceramic solid electrolyte material for Li-ion batteries. In this study, atomistic simulation techniques were employed to examine intrinsic defect processes; long range Li-ion migration paths, together with activation energies; and candidate substitutional dopants at the Zn and the Si sites in both monoclinic and orthorhombic Li2ZnSiO4 phases. The Li-Zn anti-site defect is the most energetically favourable defect in both phases, suggesting that a small amount of cation mixing would be observed. The Li Frenkel is the second lowest energy process. Long range Li-ion migration is observed in the ac plane in the monoclinic phase and the bc plane in the orthorhombic phase with activation energies of 0.88 eV and 0.90 eV, respectively, suggesting that Li-ion diffusivities in both phases are moderate. Furthermore, we show that Fe3+ is a promising dopant to increase Li vacancies required for vacancy-mediated Li-ion migration, and that Al3+ is the best dopant to introduce additional Li in the lattice required for increasing the capacity of this material. The favourable isovalent dopants are Fe2+ at the Zn site and Ge4+ at the Si site.

Crystallization characteristics and physico-chemical properties of glass–ceramics based on Li2O–ZnO–SiO2 system

Glass materials based on lithium zinc silicate system of the composition 24Li2O–20ZnO–56SiO2 LZS (mol%) were prepared and converted to glass–ceramics using controlled heat-treatment schedules. The LZS base glass system was modified by addition of Al2O3 and MO/ZnO replacements where MO=CaO, CdO and SrO oxides. Several crystalline phases were developed, including lithium zinc orthosilicate, α-quartz, β-spodumene solid solution, lithium meta and disilicate, Ca-wollastonite, Cd or Sr metasilicate, and Sr-zinc silicate of hardystonite type. The effects of crystallization process on some properties, like thermal expansion coefficient (TEC), chemical stability, and density of glass–ceramics were evaluated. The TEC of crystalline samples varied from 72×10−7 to 149×10−7K−1, 25–600 and density values in the range, 2.67–3.29g/cm3. The addition of Al2O3 and MO/ZnO replacements in the base glass led to improve the chemical durability of the glass–ceramics samples. As a result of the thermal and physico-chemical properties of the studied glass–ceramic, the materials acquire excellent properties and can be used to seal a variety of different metals and alloys.

Effect of CuO addition on crystallization and thermal expansion properties of Li2O–ZnO–SiO2 glass-ceramics

A Li2O-ZnO-SiO2 (LZS) glass system was modified with CuO, and its phase development, microstructure evolution, crystallization kinetics and thermal expansion properties were investigated as a function of heat treatment temperature. As a result of the X-ray diffraction study and microstructure observation, lithium zinc silicate formed as the first crystalline phase with increasing heat treatment temperature. Silica polymorph developed as minor crystalline phase at higher temperatures. From the X-ray diffraction patterns, CuO addition led to a decrease in both the crystallization temperature of lithium zinc silicate phase and the volume fraction of quartz phase. According to the crystallization kinetics, the crystallization activation energy for lithium zinc silicates is almost equal to the diffusion activation energy of Zn2+ in glass, it suggests that the diffusion of network modifier Zn2+ dominates the crystallization of lithium zinc silicates. Additionally, CuO addition caused the transition of Zn2+ from network modifiers to network formers. From the thermal expansion coefficient measurements, two abrupt changes in slope of the thermal expansion curves were observed and attributed to the phase transitions of cristobalite and lithium zinc silicate, respectively. Comparison of the thermal expansion coefficient of two types of glass-ceramics revealed that CuO addition in the LZS system can partly inhibit the formation of cristobalite at high temperatures.

Crystallization and thermal expansion behavior of lithium zinc silicate sealing glass

Effect of heat treatment schedule on the crystallization and thermal expansion behavior of a lithium zinc silicate glass system was investigated by differential scanning calorimeter (DSC), X-ray diffraction, and linear thermal expansion test. Two well-defined crystallization exothermic peaks were observed from the DSC trace. According to the apparent activation energies and avrami parameter values calculated from the two crystallization exothermal peaks, the first crystallization exothermal peak was attributed to a combining surface and internal crystallization behavior, while the second one was found to be internal crystallization. Additionally, the phase evolution and the thermal expansion behavior with increasing heat treatment temperature were found to be closely related. Interestingly, it was found in comparison with previous reports that addition of CaO varies the phase composition of the resulting glass–ceramic in an opposite way to K2O and the deep rooted reason has been discussed which may cast light on the modulation of properties of glass–ceramic involved crystalline phase of quartz or cristobalite. At last, average thermal expansion coefficient of 7.99–15.38×10−6K−1 in the temperature range of 25–400°C has been obtained with different heat treatment schedules.

Crystallization and thermo-mechanical properties of Li2O-ZnO-CaO-SiO2 glass-ceramics with In2O3 and Fe2O3 additives

Li2O-ZnO-CaO-SiO2 based glasses were prepared by the conventional melting technique and subsequently converted to glass-ceramics by controlled crystallization. The nucleation and crystallization temperatures were determined by differential thermal analysis (DTA). The effects of adding In2O3 and Fe2O3 addition on the crystallization behaviour and thermo-mechanical properties of the prepared glass-ceramics were investigated. A study on the microstructure, close to the internal phases of the resulting glass-ceramics, was followed by using scanning electron microscope (SEM). The dilatometric thermal expansion and Vickers? microhardness of the crystalline products were also evaluated. The crystalline phases that can be found in the resulting glass-ceramics, identified by X-ray diffraction (XRD) analysis, are ?-quartz-[SiO2], lithium zinc silicate-[Li2ZnSiO4], lithium disilicate-[Li2Si2O5], wollastonite-[CaSiO3], wollastonite containing iron, ferrobustamite-[(Ca0.79Fe0.21)SiO3], and lithium indium silicate of pyroxene type-[LiInSi2O6]. Average thermal expansion coefficient (in the temperature range 25-700?C) decreased from 191?10-7 1/?C to 115?10-7 1/?C and the Vickers? microhardness increased from 3.56 to 5.44GPa with the increase of In2O3 and Fe2O3 contents in the glass-ceramics. The changes in the obtained expansion coefficient and microhardness were due to the formation of different phases which in turn influenced the rigidity/bonding and microstructure in the resultant glass-ceramics.

Fluorescence and thermal stress properties of Yb3+-doped alumino silicate glasses for ultra high peak power laser applications

Various alumino silicate glasses (network modifier ions: Li+, Mg2+, Zn2+ and/or La3+) doped with 1 × 1020 Yb3+ cm−3 (about 0.2 mol% Yb2O3) were prepared. The glasses were studied with respect to their thermo-mechanical and fluorescence properties. Huge differences are found for the coefficients of thermal expansion which determine the thermal shock resistance of the material and hence are required for ultra-high power laser applications. Here, zinc and magnesium alumino silicate glasses show the lowest values. The fluorescence lifetimes of the glasses increase with decreasing average atomic weight of the glass composition (685–1020 µs). All glasses show broad and smooth emission spectra with little variations due to compositional changes.Mixed lithium zinc or lithium magnesium alumino silicate glasses could be promising new laser materials especially with respect to ultra-high peak power systems or applications with high repetition rates.

Effect of BaO on Thermo-Physical Properties of Lithium Zinc Silicate Glass-Ceramics

Lithium zinc silicate (LZS) glasses containing Li2O–ZnO–SiO2–Na2O–B2O3–BaO–P2O5 with different BaO/(BaO+ZnO) ratios were prepared by conventional melt and quench technique and subsequently converted into glass-ceramics. The effect of BaO/(BaO+ZnO) ratio on various thermo-physical properties was investigated by changing the ratio from 0 to 0.226. The crystalline phases were characterized by X-ray diffraction technique on the composite glass-ceramics, including Li3Zn0.5SiO4, Li2OZnSiO4 and cristobalite phase. The thermal expansion coefficient (TEC) in the temperature range 70–400 oC increased from 107 × 10-7 to 141 ×10-7 / oC. The increase in expansion coefficient was associated with the formation of different phases which in turn influenced the rigidity/bonding in the glass-ceramics. The microstructure was analyzed by scanning electron microscopy (SEM), and the grain size became bigger after the addition of BaO.

Structural, Thermal and Dielectric Properties of Lithium Zinc Silicate Ceramic Powders by Sol-Gel Method

We have developed novel cathode materials in the chemical composition of Li2ZnSiO4, Li1.5Zn1.5SiO4, Li1Zn2Sio4, Li0.5Zn2.5SiO4 and Zn2SiO4 by a sol-gel method. Structural and thermal properties of these materials have been carried out from the measurement of their XRD, FTIR, and TG-DTA profiles. For the Zn2SiO4 sample, the optimized synthesis temperature has been found to be 900°C and maintaining this temperature; the remaining other samples have also been developed for their analysis. The ac conductivity, dielectric constant, dielectric loss values have been obtained and their trends have been explained on the basis of the distribution of Li+ ions in them because of their display of Maxwell- Wagner interfacial- type polarization.

Broadband UV-to-green photoconversion in V-doped lithium zinc silicate glasses and glass ceramics

We report on photoluminescence of vanadium-doped lithium zinc silicate glasses and corresponding nanocrystalline Li2ZnSiO4 glass ceramics as broadband UV-to-VIS photoconverters. Depending on dopant concentration and synthesis conditions, VIS photoemission from [VO4]3 is centered at 550-590 nm and occurs over a bandwidth (FWHM) of ~250 nm. The corresponding excitation band covers the complete UV-B to UV-A spectral region. In as-melted glasses, the emission lifetime is about 34 μs up to a nominal dopant concentration of 0.5 mol%. In the glass ceramic, it increases to about 45 μs. For higher dopant concentration, a sharp drop in emission lifetime was observed, what is interpreted as a result of concentration quenching. Self-quenching is further promoted by energy transfer to V4+ centers (2<Гt4→2Гt3). Partitioning of vanadium into V5+ and V4+ was examined by electron paramagnetic resonance and X-ray photoelectron spectroscopy. Suppression of V5+-reduction requires careful adjustment of the optical basicity of the host glass and/or synthesis conditions.

Electrical behaviour of Li 2O–ZnO–SiO 2 glass and glass-ceramics system

Sealing quality lithium zinc silicate (LZS) glasses of compositions (wt.%) (a) LZSL– Li 2O: 12.65, ZnO: 1.85, SiO 2: 74.4, Al 2O 3: 3.8, K 2O: 2.95, P 2O 5: 3.15, B 2O 3: 1.2 (low ZnO), and (b) LZSH– Li 2O: 8.9, ZnO: 24.03, SiO 2: 53.7, Na 2O: 5.42, P 2O 5: 2.95, B 2O 3: 5 (high ZnO) were prepared by conventional melt-quench technique and converted to glass-ceramics by controlled crystallization process. The electrical properties of these samples were measured using ac impedance spectroscopy technique over a frequency range of 10 Hz–15 MHz at several temperatures in the range of 323–673 K. The ac conductivity, dc conductivity, dielectric constant and loss factor were obtained from these measurements. The dc conductivity ( σ dc) follows the Arrhenius behaviour with temperature. It is observed that σ dc in LZSL glass is significantly higher than in the LSZH glass and the activation energies for σ dc for LZSL and LZSH glasses are 0.59 and 1.08 eV, respectively. It further observed that the conductivity value decreases nearly one order of magnitude on conversion to glass-ceramics. The behaviour is explained on the basis of distributions and nature of alkali ions and network structures in these samples.

The effect of NiO on the phase formation, thermo-physical properties and sealing behaviour of lithium zinc silicate glass–ceramics

We have prepared lithium zinc silicate (LZS) glasses of compositions (mol%) 17.83Li2O–17.73ZnO–(53.52 − x)SiO2–5.25Na2O–1.25P2O5–4.31B2O3–x-NiO, where 0.5 ≤ x ≤ 2.0, by the melt quench technique. The effect of NiO on the phase formation, thermo-physical properties and sealing behaviour of LZS glass–ceramics was studied using X-Ray diffraction (XRD), thermo-mechanical analysis (TMA) and microhardness (MH) measurements. It is found that NiO incorporation leads to a change in the role of ZnO from network modifier to intermediate oxide. The intermediate network forming Zn2+ ions would find it more difficult to diffuse and initiate the transformation of Li3Zn0.5SiO4 to Li2ZnSiO4. Thus Li3Zn0.5SiO4 is formed instead of Li2ZnSiO4 on addition of 2 mol% NiO. Scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX) measurements at the glass–ceramic-to-metal interface reveal a change in the microstructure commensurate with the changing role of ZnO. Addition of NiO favoured interdiffusion of species at the interface leading to better sealing.

Thermophysical and structural studies on some glass-ceramics and role of nano size crystallites

In this paper, we present some studies on structure and thermophysical properties of glass and glass-ceramics with possible bio-medical and sealing applications. The glass-ceramics prepared for bio-medical applications include phosphate as well as silico-phosphate compositions. In vitro bio-compatibility/activity of these materials is discussed. The glass-ceramics used for the sealing application are lithium aluminium silicate (LAS) and lithium zinc silicate (LZS). The phase formation and some aspects of thermophysical properties and sealing are discussed.

Some developments on ceramic-to-metal and glass-ceramics-to-metal seals and related studies

Seals and coatings based on ceramics and glass-ceramics find numerous applications in different disciplines of science and technology including space, accelerators, nuclear energy, chemical industry. Ceramic-to-metal (CM) seals based on conventional design (using brazing alloys) and glass-ceramics have been prepared. While Ag-Cu brazing alloy has been used in conventional CM seal, we have employed lithium zinc silicate (LZS) and lithium aluminum silicate (LAS) glass-ceramics for glass-ceramics-to-metal (GCM) seals. LZS glass-ceramics based on two different compositions; (a) LZSL composition (wt.%)- Li2O: 12.65, ZnO: 1.85, SiO2: 74.4, Al2O3: 3.8, K2O: 2.95, P2O5: 3.15, and B2O3: 1.2 (low ZnO) and (b) LZSH composition (wt.%)- Li2O: 8.9, ZnO: 24.03, SiO2: 53.7, Na2O: 5.42, P2O5: 2.95, and B2O3: 5.0 (high ZnO) were prepared with desired sealing characteristics for matched type seals. In addition, (wt.%) 12.6Li2O-71.7SiO2-5.1Al2O3-4.9K2O-3.2B2O3−2.5P2O5 (LAS-GC) was investigated for compressive type of seal. LZS glass-ceramics-to-Cu as well as SS-321 seals were found to withstand a vacuum of 10−6 Torr with leak rate 10−9 Torr. 1/s and LAS GC-to-SS304 seal showed high pressure endurance of 12000psi. In order to understand the mechanism of sealing, glass-ceramics-to-metal interface study has also been carried out.

Interfacial Reactions in Glass–Ceramic‐to‐Metal Seals

During the sealing of glass–ceramics to metals, undesirable interfacial reactions may occur between constituents of the glass and diffusing metal species, and any reaction products formed may have serious consequences on the lifetime behavior of seal components. This paper reviews the factors influencing the lifetime behavior of glass–ceramic‐to‐metal systems, with particular emphasis given to the effect that such interfacial reactions can have on the resultant and longer term properties. Steps that can be taken to enhance desirable interfacial reactions and minimize those that are undesirable are highlighted. In addition, in order to aid in the understanding of complex alloy systems, it is of interest to study both the interfacial reactions and diffusion characteristics of simplified systems without the complicating issue of multiple element diffusion. Thus, a preliminary investigation is highlighted in which a lithium zinc silicate glass nucleated with P2O5 has been sealed to high‐purity Fe, Ni, and Cr metals and the resultant diffusion into the glass of each metal monitored as a function of sealing temperature and time. The data generated have been compared with information from multicomponent alloy systems and an attempt has been made to explain the differences noted.

MAS-NMR study of lithium zinc silicate glasses and glass-ceramics with various ZnO content

Lithium zinc silicate glasses of composition (mol%): 17.5Li 2O–(72− x)SiO 2– xZnO−5.1Na 2O−1.3P 2O 5−4.1B 2O 3, 5.5⩽ x⩽17.7, were prepared by conventional melt-quenched technique and converted to glass-ceramic by controlled crystallization process. 29Si and 31P MAS-NMR was used to characterize the structure of both glass and glass-ceramic samples. Despite the complex glass composition, Q 2, Q 3 and Q 4 sites are identified from 29Si MAS-NMR, which relative intensities are found to vary with the ZnO content, indicating a network depolymerization by ZnO. Moreover, well separated Q 3 and Q 4 resonances for low ZnO content indicates the occurrence of phase separation. From 31P MAS-NMR, it is seen that phosphorus is mainly present in the form of ortho-( Q 0) and pyro-phosphate ( Q 1) structural units and variation of ZnO content did not have much effect on these resonances, which provides an additional evidence for phase separation in the glass. On conversion to glass-ceramics, lithium disilicate (Li 2Si 2O 5), lithium zinc ortho-silicate (Li 3Zn 0.5SiO 4), tridymite (SiO 2) and cristobalite (SiO 2) were identified as major silicate crystalline phases. Using 29Si MAS-NMR, quantification of these silicate crystalline phases is carried out and correlated with the ZnO content in the glass-ceramics samples. In addition, 31P spectra unambiguously revealed the presence of crystalline Li 3PO 4 and (Na,Li) 3PO 4 in the glass-ceramics.

The influence of Ta2O5 additions on the thermal properties and crystallization kinetics of a lithium zinc silicate glass

The lithium zinc silicate glass exhibits two crystallization exotherms corresponding to the formation of Li2ZnSiO4 and silica phases, respectively. The silica phases include tridymite and cristobalite. The influence of Ta2O5 additions on the thermal properties and non-isothermal crystallization kinetics of this glass, including nucleation rate maxima and activation energies for crystallization, has been determined by differential scanning calorimetry and X-ray diffraction. It has been found that Ta2O5 affects the crystallization behavior markedly, inhibiting the crystallization of high thermal expansion silica phases at lower concentrations, whilst at higher concentrations also suppressing crystallization of the Li2ZnSiO4 phase. At the higher concentrations, these phases are replaced by small amounts of LiTaO3 and LiTaSiO5.