Characterization of SiO2–Na2O–Fe2O 3–CaO–P2O 5–B 2O 3 glass ceramics

Bioactivity and magnetic properties were investigated in glass and glass ceramics based on the SiO₂–Na₂O–Fe₂O₃–CaO–P₂O₅–B₂O₃ system to find their suitability as thermoseed for hyperthermia treatment of cancer. The effect of change in compositions on bioactivity was examined in simulated body fluids. The glass ceramic samples exhibit Na₃CaSi₃O₈ and Na_3-XFe_XPO₄ phases. After dipping the glass ceramic samples in simulated body fluids silica hydrogel first forms, followed by an amorphous calcium phosphate layer. Magnetic and microwave resonance experiments further demonstrate the potential of these glass ceramics for possible use in hyperthermia.     

Electrical conductivity studies of Bi2O3–Li2O–ZnO–B2O3 glasses

Ac conductivity measurements and its analysis has been performed on xBi₂O₃–(65?x)Li₂O–20ZnO–15B₂O₃ (0 ≤ x ≤ 20) glasses in the temperature range 30–300 °C and a frequency range of 100 Hz to 1 MHz. The dc conductivity increased and the activation energy decreased with lithium content. The frequency dependent conductivity has been analyzed employing conductivity and modulus formalisms. The onset of conductivity relaxation shifts towards higher frequencies with temperature. The Almond–West conductivity formalism is used to explain the scaling behavior, and the relaxation mechanism is independent of temperature.     

Phase Relations in the Na2O–Al2O3–Nb2O5and CaO–Al2O3–Nb2O5Systems

Phase relations in the Na₂O–Al₂O₃–Nb₂O₅and CaO–Al₂O₃–Nb₂O₅systems were studied. The Na₂O system was found to contain neither ternary compounds nor niobate–aluminate solid solutions. In the CaO system, a ternary compound of composition 4CaO · Al₂O₃·Nb₂O₅was identified (cubic structure, a= 7.628 Å, Z= 2, _meas= _x= 4.43 g/cm³).     

Phase Relations in the Systems Al2TiO5–Fe2O3 , Al2O3–TiO2–Fe2O3 , and Al2TiO5–Cr2O3

Phase relations in the systems Al₂TiO₅–Fe₂O₃, Al₂TiO₅–Cr₂O₃, and Al₂O₃–TiO₂–Fe₂O₃ are investigated, and the composition ranges of pseudobrookite Al_{2 – 2x} M_2x TiO₅ (M = Fe, Cr) solid solutions are determined.     

Surface crystallization and second-order optical non-linearity in Gd2O3–Bi2O3–B2O3 glasses

Some ternary Gd₂O₃–Bi₂O₃–B₂O₃ glasses are prepared, and crystallization behavior and second harmonic intensity are examined to develop new non-linear optical crystallized glasses. The glasses with Gd₂O₃ contents of 8–14 mol% have large densities of over 6 g/cm³ and large refractive indices of ～ 1.9. Transparent surface crystallized glasses consisting of two kinds of crystalline phases with different morphologies, i.e. plate shape and needle shape crystals, are fabricated by heat-treatment at temperatures between glass transition and crystallization temperatures. From second harmonic generation microscope observations, micro-Raman scattering spectra and XRD analyses, plate shape crystals are determined to be non-linear optical Gd_xBi_1KxBO₃ and needle shape crystals are Bi₃B₅O₁₂ having no second-order optical non-linearity. Since crystallized glasses consisting of Gd_xBi_1KxBO₃ crystals exhibit relatively strong SHGs, they have a high potential for application to light control devices.     

Surface crystallization and second-order optical non-linearity in Gd2O3–Bi2O3–B2O3 glasses

Some ternary Gd₂O₃–Bi₂O₃–B₂O₃ glasses are prepared, and crystallization behavior and second harmonic intensity are examined to develop new non-linear optical crystallized glasses. The glasses with Gd₂O₃ contents of 8–14 mol% have large densities of over 6 g/cm³ and large refractive indices of ∼1.9. Transparent surface crystallized glasses consisting of two kinds of crystalline phases with different morphologies, i.e. plate shape and needle shape crystals, are fabricated by heat-treatment at temperatures between glass transition and crystallization temperatures. From second harmonic generation microscope observations, micro-Raman scattering spectra and XRD analyses, plate shape crystals are determined to be non-linear optical Gd_xBi_1−xBO₃ and needle shape crystals are Bi₃B₅O₁₂ having no second-order optical non-linearity. Since crystallized glasses consisting of Gd_xBi_1−xBO₃ crystals exhibit relatively strong SHGs, they have a high potential for application to light control devices.     

Microwave dielectric properties of 3Li2O–Nb2O5–3TiO2 ceramics with Li2O–V2O5 additions

A new Li₂O–Nb₂O₅–TiO₂ (LNT) ceramic with the Li₂O:Nb₂O₅:TiO₂ mole ratio of 3:1:3 has been investigated. The compound is composed of two phases, the Li₂TiO₃ and “M-phase” solid solution phase. The microwave dielectric ceramic has low sintering temperature (∼1100 °C) and good microwave dielectric properties of a relatively high permittivity (∼51), high Q × f value up to 8700, and small temperature coefficient (∼37 ppm/°C). The low-amount doping of 0.83Li₂O–0.17V₂O₅ (LV) can effectively lower the sintering temperature from 1100 to 900 °C and induce no obvious degradation of the microwave dielectric properties. Typically, the 1 wt.% LV-doped ceramic sintered at 900 °C has better microwave dielectric properties of ε_r = 51.3, Q × f = 7235 GHz, τ _f  = 22 ppm/°C, which suggests that the ceramics can be applied in microwave LTCC devices.     

Phase Relations in the SrO–Bi2O3–Fe2O3 System

The phase relations in the composition region SrFeO_{3 –} –Fe₂O₃–BiFeO₃ are studied in air by x-ray diffraction and electron microscopy. The 1000°C phase compatibility diagram is constructed. Sr_{1 – x} Bi _x FeO_{3 –} solid solutions are prepared in the range 0 < x 0.8. Their lattice parameter is found to vary nonlinearly with x. Two new phases were identified: (Sr,Bi)₃Fe₄O _y (tetragonal lattice, a= 3.907(2) Å, c= 27.30(2) Å) and Sr_0.6Bi_0.4FeO_{3 –} (tetragonal lattice,a = 5.555(2) Å, c= 11.848(5) Å).     

Characterisation of Ga2O3–Na2O–CaO–ZnO–SiO2 bioactive glasses

The structural role of Gallium (Ga) is investigated when substituted for Zinc (Zn) in a 0.42SiO₂–0.40–xZnO–0.10Na₂O–0.08CaO glass series, (where x = 0.08). Each starting material was amorphous, and the network connectivity (NC) was calculated assuming Ga acts as both a network modifier (1.23), and also as a network former. Assuming a network forming role for Ga the NC increased with increasing Ga concentration throughout the glass series (Control 1.23, TGa-1 2.32 and TGa-2 3.00). X-ray photoelectron spectroscopy confirmed both composition and correlated NC predictions. Raman spectroscopy was employed to investigate Q-structure and found that a shift in wavenumbers occurred as the Ga concentration increased through the glass series, from 933, 951 to 960 cm^?1. Magic angle spinning nuclear magnetic resonance determined a chemical shift from ?73, ?75 to ?77 ppm as the Ga concentration increased, supporting Raman data. These results suggest that Ga acts predominantly as a network former in this particular Zn-silicate system.     

Liquid-phase bonding of silicon nitride ceramics using Y2O3–Al2O3–SiO2–TiO2 mixtures

Hot-pressure sintered β-Si₃N₄ ceramic was bonded to itself using Y₂O₃–Al₂O₃–SiO₂–TiO₂ mixtures. Reactive behavior at interface between Si₃N₄ and Y₂O₃–Al₂O₃–SiO₂–TiO₂ mixtures during silicon nitride ceramic joining was studied by means of scanning electron microscopy (SEM), electron probe microanalyses (EPMA), X-ray diffraction (XRD) and auger electron spectroscopy (AES). The joint strength under different bonding conditions was measured by four-point bending tests. The results of EPMA, AES and XRD analyses show that the liquid glass solder reacts with silicon nitride at interface, forming the Si₃N₄/Y–Si–Al–Ti–O–N glass/TiN/Y–Si–Al–O glass gradient interface. From the results of four-point bending tests, it is known that with increase of bonding temperature and holding time, the joint strength increased reaching a peak, and then decreased. The maximum joint strength of 200 MPa measured by the four-point bending tests is obtained for silicon nitride bonded at 1823 K for 30 min.     

EPR and magnetic susceptibility studies of Cr2O3–Bi2O3–GeO2 glasses

Electron paramagnetic resonance (EPR) and magnetic susceptibility measurements have been performed on xCr2O3(1–x)[Bi2O3·GeO2] glasses with 0相似文献   

Phase Relations in the BaO · 2B2O3–La2O3 · 3B2O3 System

The BaO · 2B₂O₃–La₂O₃ · 3B₂O₃ join of the ternary system BaO–La₂O₃–B₂O₃ is studied using differential thermal analysis, x-ray diffraction, and density measurements. The join is shown to be pseudobinary, with eutectic phase relations. In the composition range 5–99.8 mol % La₂O₃ · 3B₂O₃, glassy materials are obtained, which seems to be associated with the existence of the congruently melting compound BaO · La₂O₃ · 5B₂O₃.     

Microwave dielectric properties of CaO–La2O3–Nb2O5–TiO2 ceramics

A series of ceramics with a general formula Ca_1+xLa_4?xNb_xTi_5?xO₁₇ (0 ≤ x ≤ 4) were fabricated using the solid-state ceramic route. The phase, microstructure, and microwave dielectric properties varied distinctly with composition or the value of x. X-ray diffraction results showed that the two end member phases, CaLa₄Ti₅O₁₇ and Ca₅Nb₄TiO₁₇, crystallized into single phases with orthorhombic and monoclinic crystal structure, respectively. For intermediate compounds with x = 1, 2, and 3, mixture phases CaLa₄Ti₅O₁₇ and Ca₅Nb₄TiO₁₇ coexisted and a trace amount of second phase was detected. The ceramics showed high ε _r in the range of 45–52, relatively high quality factors with Q × f in the range of 9,870–15,680 GHz and τ _f value in the range between ?38 and ?126.4 ppm/°C. τ _f of CaLa₄Ti₅O₁₇ can be tuned to a near-zero value by addition of suitable amount of TiO₂.     

On the development of two characteristically different crystal morphology in SiO2–MgO–Al2O3–K2O–B2O3–F glass-ceramic system

The present work demonstrates how crystals with two different characteristic morphologies can be formed in SiO₂–MgO–Al₂O₃–K₂O–B₂O₃–F glass-ceramic system by adopting two sets of heat treatment experiments. In our study, single stage heat treatment experiments were performed at 1,000°C for varying holding time of 8–24 h with 4 h time interval and as a function of temperature in the range of 1,000–1,120°C with 40°C temperature interval. The constant heating rate of 10°C/min was employed for both sets of experiments. The microstructural changes were investigated using Fourier transformed infrared spectroscopy (FT-IR), SEM-EDS and XRD. For temperature variation batches, the microstructure is characterized by interlocked, randomly oriented mica plates (‘house-of-cards’ morphology). An important and new observation of complex crystal morphology is made in the samples heat treated at 1,000°C for varying holding times. Such morphology appears to be the results of composite spherulitic-dendritic like growth of mica rods radiating from a central nucleus. The possible mechanism for such characteristic crystal growth morphology is discussed with reference to a nucleation-growth kinetics based model. The activation energy for crystal nucleation and Avrami index are computed to be 388 kJ/mol and 1.3 respectively, assuming Johnson–Mehl–Avrami model of crystallization. Another important result is that a maximum of around 70% of spherulitic-dendritic like crystal morphology can be obtained after heat treatment at 1,000°C for 24 h, while a lower amount (~58%) of interlocked plate like mica crystals is formed after heat treatment at 1,040°C for 4 h.     

Ion-Conducting Defect Pyrochlore Phases in the K2O–Sb2O3–WO3 System

Potassium tungstate antimonates were prepared by calcining K₂CO₃ + Sb₂O₃ + 2(1 – – )WO₃ mixtures in air. Data on the phase composition of the obtained materials were used to locate the pyrochlore phase region in the Sb₂O _z –W₂O₆ – K₂O composition triangle at 1170 K. The distributions of the constituent ions and lattice defects over the crystallographic positions of space group Fd3m were inferred from structural and gravimetric data. The ac conductivity of the potassium tungstate antimonates was measured from 600 to 1000 K. The conductivity and its activation energy were shown to be correlated with the concentrations of cation (position 16d) and anion (position 8b) defects. The concentration and mobility of K⁺ ions involved in charge transport were determined.     

Mössbauer Study of Tetragonal ZrO2–Y2O3–Fe2O3 Solid Solutions

Tetragonal Zr_0.886Y_0.057Fe_0.057O_{2 –} solid solutions prepared by calcining coprecipitated and successively precipitated hydroxide mixtures were studied by Mössbauer spectroscopy immediately after calcination and after long-term storage. The results indicate that the solid solutions prepared via coprecipitation and successive precipitation contain Fe³⁺ in two (octahedral coordination) and three (octahedral, fivefold, and tetrahedral coordinations) inequivalent sites, respectively. Partial Fe³⁺ substitution for Y³⁺ is shown to prevent or substantially slow down the low-temperature structural degradation of stabilized zirconia.     

BaWO4–BaCuO2–Y2Cu2O5–“1010” Section of the Y2O3–BaO–WO3–CuO System

The phase region of cubic perovskite-like solid solutions (a = 8.28–8.40 Å) in the Y₂O₃–BaO–WO₃–CuO system is outlined, and the phase compatibility diagram of the BaWO₄–BaCuO₂–Y₂Cu₂O₅–1010 (1010 = Y₂WO₆ + Y₂W₃O₁₂) is constructed.     

Selection of eutectic systems in AI2O3–Y2O3 ceramics

There are two eutectic reactions in the Al₂0₃–rich portion of the AI₂O₃-Y₂O₃ pseudo–binary system; one is the equilibrium A1₂0₃–YAG eutectic reaction at 1826%C, and the other is the metastable A1₂0₃–YAP eutectic reaction at 1702%C. Selection of the A1₂0₃–YAG and the A1₂0₃–YAP eutectics was examined in terms of cooling rate, nucleation temperature and maximum melt temperature. When the melt was cooled from 2100%C at any cooling rate, it always nucleated below the Al₂0₃–YAP eutectic temperature, therefore the Al₂0₃–YAP eutectic was selected. The Al₂0₃–YAG eutectic was selected when the melt was cooled from 1900%C at a cooling rate of less than 1 K s^-1. The selection of the two eutectic systems was determined by the nucleation temperature, although the maximum holding temperature of the melt and the cooling rate significantly affected the nucleation temperature. The structure of the melt, such as coordination of oxygen and chemical order when being heated to 2100%C may affect the nucleation behavior.     

Spectroscopic properties of B2O3–PbO–Bi2O3–GeO2 glass doped with Sm3+ and gold nanoparticles

Heavy metal oxide B₂O₃–PbO–Bi₂O₃–GeO₂ transparent glass doped with Sm³⁺ was synthesized and implanted with Au⁺ using energy of 300 keV and fluence of 1 × 10¹⁶ cm⁻². The annealing of the implanted glass at moderate temperature below the glass transition temperature induced the nucleation of gold nanoparticles, confirmed by the characteristic absorption band in the visible range and by transmission electron microscopy. Using Miés and Doylés theories for the surface plasmon resonance, the average size of the gold nanoparticles was about 4.6 nm, similar to the values observed by transmission electron microscopy. It was also observed the crystallization of a thin layer of the glass at the implanted surface after annealing, detected by X-ray diffraction and scanning electron microscope. Visible and near-infrared emission of Sm³⁺ was enhanced after annealing of the glass implanted with gold. Judd–Ofelt parameters and radiative parameters were calculated for the glass doped with Sm³⁺ with and without gold nanoparticles.     

Crystallization of R2O–MgO–Al2O3–B2O3–SiO2–F (R=K+, Na+) glasses with different fluorine source

The effect of fluorine source on the crystallization behaviors of the R₂O–MgO–Al₂O₃–B₂O₃–SiO₂–F (R=K⁺, Na⁺) glasses is studied by differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectrum. Two glasses with the same composition were prepared by using NaF and MgF₂ as the source of fluorine, respectively. The glass with the fluorine source of NaF is quite stable during heat-treatment. Only large dendrite crystals form on the surface of this glass, while the interior of the glass still remains amorphous. In contrast, the glass with the fluorine source of MgF₂ exhibits uniform bulk crystallization and forms mica-containing glass-ceramics after heat-treatment. The structure difference between these two glasses was investigated by Raman spectrum. The glass with the fluorine source of NaF shows a simple Raman spectrum. Boroxol rings are found to be the dominant unit in this glass. In contrast, multiple peaks appear on the Raman spectrum of the glass with the fluorine source of MgF₂, and these peaks are resolved to the vibrations of three- or four-coordinated boron units, such as chain-type metaborate groups, pentaborate groups, diborate groups, highly changed orthoborate groups, pyroborate groups, as well as boroxol rings. The stability of the glass with the NaF fluorine source is attributed to the high stability of the boroxol rings in this glass.