Glass-ceramic Method Research Articles

Synthesis and Research of Critical Parameters of Bi-HTSC Ceramics Based on Glass Phase Obtained by IR Heating

In this paper influence of the excess Ca and Cu cations on the critical temperature (Tc) and critical transport current density (Jc) of high-temperature superconducting ceramics of the compositions (HTSC) Bi1.6Pb0.4Sr2Ca2.1Cu3.1Oy, Bi1.6Pb0.4Sr2Ca2.25Cu3.25Oy and Bi1.6Pb0.4Sr2Ca3Cu4Oy synthesized by the glass-ceramic method has been studied. The synthesis of superconducting ceramics was carried out on the basis of the glass phase, obtained by ultra-fast quenching of the melt. Melting of the mixture of starting components was carried out without the use of a crucible under the influence of IR radiant heating. Analysis of the elemental composition of the samples of the initial precursors showed a significant deviation from stoichiometry in oxygen (increase), as well as a decrease in calcium content. The synthesis of HTSC ceramics was carried out at a temperature of 849–850 °C for 96 h with intermediate grinding every 24 h. Studies of the phase composition of ceramic samples by X-ray diffraction have shown that HTSC ceramics consist only of a superconducting high-temperature phase Bi-2223. Studies of current-carrying characteristics by the four-point probe method according to the criterion of 1 µV/cm2 have shown that high-temperature superconducting ceramics of the compositions Bi1.6Pb0.4Sr2Ca2.1Cu3.1Oy, Bi1.6Pb0.4Sr2Ca2.25Cu3.25Oy and Bi1.6Pb0.4Sr2Ca3Cu4Oy have an increased density of critical transport current of 9.12 A/cm2, 7.62 A/cm2 and 7.26 A/cm2, respectively. At the same time, it was found that with a decrease in the content of Ca and Cu cations in HTSC ceramics, an increase in the critical current density is observed.

Solid Electrolyte Membranes Based on Li2O-Al2O3-GeO2-SiO2-P2O5 Glasses for All-Solid State Batteries.

Rechargeable Li-metal/Li-ion all-solid-state batteries due to their high safety levels and high energy densities are in great demand for different applications ranging from portable electronic devices to energy storage systems, especially for the production of electric vehicles. The Li1.5Al0.5Ge1.5(PO4)3 (LAGP) solid electrolyte remains highly attractive because of its high ionic conductivity at room temperature, and thermal stability and chemical compatibility with electrode materials. The possibility of LAGP production by the glass-ceramic method makes it possible to achieve higher total lithium-ion conductivity and a compact microstructure of the electrolyte membrane compared to the ceramic one. Therefore, the crystallization kinetics investigations of the initial glass are of great practical importance. The present study is devoted to the parent glasses for the production of Li1.5+xAl0.5Ge1.5SixP3-xO12 glass-ceramics. The glass transition temperature Tg is determined by DSC and dilatometry. It is found that Tg decreases from 523.4 (x = 0) to 460 °C (x = 0.5). The thermal stability of glasses increases from 111.1 (x = 0) to 188.9 °C (x = 0.3). The crystallization activation energy of Si-doped glasses calculated by the Kissinger model is lower compared to that of Si-free glasses, so glass-ceramics can be produced at lower temperatures. The conductivity of the glasses increases with the growth of x content.

Near-infrared responsive upconversion glass-ceramic@BiOBr heterojunction for enhanced photodegradation performances of norfloxacin

An efficient luminous and electronic energy transmission BiOBr based near-infrared (NIR) responsive heterojunction photocatalyst was successfully fabricated through growing BiOBr nanosheets on the superficial layer of the SrF2–Bi2O3–B2O3/Yb3+,Tb3+ (SBBF) upconversion glass-ceramic (GC) via a facile in-situ etching GC method (FIEG). A high norfloxacin (NOR) degradation rate of 56% was obtained under 180 min NIR light irradiation for the NIR GC photocatalyst (SBBF/BiOBr-10), and it possesses much enhanced photocatalytic activity compared with that of pure BiOBr under UV–vis–NIR light irradiation. Wherein six intermediate products were identified in the NOR photodegradation process and the possible degradation pathways were proposed. B3+, Yb3+ and Tb3+ ions in GC can be doped into BiOBr layer during the FIEG process. The core–shell structure of the GC@BiOBr heterojunction photocatalyst is in favor of increasing charge transport and reducing the recombination rate of excited carriers, and it efficiently harvests NIR photons to emit UV and visible light upconversion emissions, which can be utilized during the photocatalysis process. The photocatalyst can be facilely regenerated via HBr etching again, moreover, the low-cost and less time requirement promote the possibility of large-scale fabrication of the efficient photocatalysts.

Fabrication and properties of dense α-cordierite glass-ceramic coating on porous BN/Si2N2O ceramic

α-Cordierite glass-ceramic coating was fabricated on the porous BN/Si2N2O ceramic by glass-ceramic method. The effect of the heating temperature on the phase composition, microstructure, mechanical properties, water resistance and dielectric properties of the coatings was investigated. A large amount of α-cordierite precipitated from the glass phase when the heating temperature was 1050 °C and the content of α-cordierite in the coating increased with increasing the heating temperature. The resulting α-cordierite glass-ceramic coatings had a good wettability and adhesion with the porous ceramic substrate. The coating/substrate interface was continuous without defects. When the heating temperature was 1050–1200 °C, the resulting coatings possessed positive mechanical properties and good water resistance due to the high densification. And the dielectric constant and loss tangent of the coated samples prepared at 1050–1200 °C were 4.1–4.3 and 0.005–0.01 respectively in the frequency of 21–36 GHz.

Effect of holding time on microstructure, mechanical, water resistance and dielectric properties of α-cordierite glass-ceramic coating on porous BN/Si2N2O ceramic

α-cordierite glass-ceramic coating was prepared on the porous BN/Si2N2O ceramic by the glass-ceramic method at 1050 °C for 1–4 h. The effect of the holding time on the phase composition, microstructure, mechanical, water resistance and dielectric properties of the glass-ceramic coating was investigated. The resulting coating was mainly composed of α-cordierite and glass, and the α-cordierite content increased with increasing holding time. The coating/substrate interface was continuous without defects, and the glass liquid of the coating can infiltrated into the surface pores of the substrate. Additionally, the density and mechanical properties of coatings increased as the holding time increased. The obtained coated samples fabricated at 1050 °C for 2–4 h possessed a low water absorption (2.1–5%) and little open porosity (2.7–3.2%), demonstrating good water resistance. Furthermore, the coated samples prepared at 1050 °C for 3 or 4 h exhibited both low dielectric constant (4.1–4.3) and loss tangent (0.005–0.009) in the frequency range of 20–36 GHz.

Obtention and characterization of lithium superionic conductors using the glass-ceramic method

Este artículo propone la ruta vitrocerámica para obtener electrolitos sólidos por ion litio (Li+). Esta técnica provee alta homogeneidad química y microestructural, así como baja porosidad. Muestras vítreas fueron sometidas a tratamientos térmicos, simples y dobles, entre 700 °C y 1000 °C, para obtener las vitrocerámicas. Resultados de calorimetría diferencial de barrido – DSC – evidenciaron la posibilidad de fabricar estas cerámicas a partir de vidrios del sistema Li2O·Al2O3·TiO2·P2O5. Muestras observadas por microscopía electrónica de barrido – SEM – mostraron una microestructura de granos finos, homogéneamente distribuidos y sin porosidad. Patrones de difracción de rayos-x – XRD – permitieron verificar la formación de la fase altamente conductora LiTi2(PO4)3. Una conductividad iónica alta, del orden de 10-3 S/cm a 1000°C, fue medida utilizando espectroscopía de impedancia – IS. Lo anterior sugiere que el método de síntesis, utilizado en este trabajo, es útil para fabricar vitrocerámicas de ion litio y abre una nueva alternativa para fabricar diferentes cerámicas eléctricas.

Comparison of Vickers microhardness of undoped and Ru doped BSCCO glass ceramic materials

In this study, effect of substitution ratio on the mechanical and structural properties of Bi1−xRuxPb0.2Sr2CaCu2O10+δ system, that is prepared in the ratios of x = 0.0, 0.025, 0.050, 0.075, is investigated. Samples are prepared with glass ceramic method and sintered at 845 °C. XRD and SEM measurements are performed for structural analyses, and Vickers micro-hardness measurements are carried out at different applied load (0.245 ≤ F ≤ 2.940 N) in order to investigate the mechanical performance of the Ru doped Bi1−xRuxPb0.2Sr2CaCu2O10+δ system. Experimental results of Vickers micro-hardness analyses are performed using the Meyer’s law, the proportional samples resistance model, the elastic/plastic deformation model, the Hays–Kendall approach and the indentation induced cracking (IIC) model. All analyses results are exhibited reverse indentation size effect behavior. The measured hardness values increase with increasing the applied load. Finally, IIC model is determined as the most successful model describing the mechanical properties of our samples.

Ultrasonic treatment of CoFe2O4@B2O3-SiO2 as a new hybrid magnetic composite nanostructure and catalytic application in the synthesis of dihydroquinazolinones

New hybrid magnetic composite nanostructure are prepared via ultrasonic treatment by glass-ceramic method, characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), energy-dispersive X-ray (EDX), element distribution image (EDX mapping), thermal gravimetric analysis (TGA)/differential thermal analysis (DTA) and N2 adsorption-desorption by Brunauer–Emmett-Teller (BET) analyses. Then, the catalytic activity of the prepared CoFe2O4@B2O3-SiO2 nanoparticles was tested in the synthesis of 2-substituted-3-(phenylamino)-dihydroquinazolin-4(1H)-ones in deep eutectic solvent (DES) based on choline chloride as an eco-friendly and recyclable media. This novel protocol offers several advantages such as high yields (70–93%), short reaction times (10–20min), environmentally-friendly reaction media, easily isolation of the products, simple preparation and recoverability of the nanocatalysts (at least 5 times), recyclability of the solvents from the reaction mixture without use of hazardous volatile organic solvent. The catalyst was readily recycled by the use of an external magnetic field and could be reused several times without significant loss of activity or mass. The saturation magnetization of CoFe2O4@B2O3-SiO2 nanoparticles was 8.97emug−1. Their average size distribution was about 12.5nm. DES was a mixture of choline chloride and urea that was recovered from the filtrate by evaporating the water under vacuum.

Visualisation of high temperature magnetisation states in magnetite grains using off-axis electron holography

The production of a synthetic basalt comprising Fe3O4 grains (∼ 50 nm to ∼ 500 nm), via a glass ceramic method, has been confirmed using transmission electron microscopy and X-ray diffractometry. Off-axis electron holography combined with in situ heating allowed for the visualisation of non-uniform vortex states present in saturation remanent structures, and their variation approaching the Curie temperature; determined separately by bulk thermomagnetic measurements.

Synthesizing CoFe2O4 by Glass-Ceramic Method and Characterizing its Magnetic Properties in Na2O-Fe2O3-CoO-B2O3-SiO2 System

In this investigation, the effect of heat treatment on magnetic properties of glass and nano-structured cobalt-ferrite glass-ceramic was studied. The glass was synthesized in the system of Na2O-Fe2O3-CoO-B2O3-SiO2. Based on DTA results, heat treatment was done at different times and temperatures. X-ray diffraction pattern of glass-ceramic showed the crystallization * یکینورتکلا تسپ ،تابتاکم لوئسم : mirkazemi@iust.ac.ir

Structural and mechanical characterization of Bi1.75Pb0.25Sr2Ca2Cu3−xSnxO10+y superconductor ceramics using Vickers microhardness test

In this work we investigated the role of Sn doping on mechanical and structural properties of Bi1.75Pb0.25Sr2Ca2Cu3−xSnxO10+y (x = 0.0, 0.1, 0.3 and 0.5) superconducting ceramic material. All samples were fabricated with glass ceramic method. The prepared samples were characterized by using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray powder diffractometer (XRD) and static microhardness indenter. Surface morphology, orientation of grains, and elemental composition analysis of the samples were made by SEM and EDS measurements, respectively. Texturing and lattice parameters a and c were determined by XRD measurements. Load dependent and load independent microhardness, elastic modulus, yield strength and fracture toughness were obtained by hardness measurements. In this work we focused on Vickers microhardness measurements in order to characterize the mechanical properties of our samples. Experimental results of Vickers microhardness measurements were analyzed by using Meyer’s law, the elastic/plastic deformation model, proportional sample resistance model (PSR), modified PSR model and Hays-Kendall (HK) approach. From these analyses, HK approach was determined as the most successful model describing the mechanical properties of our samples. Finally in this study, the changes on the mechanical and microstructural properties of Sn doped Bi-2223 superconductors and their possible reasons were also discussed in detail.

Microstructure and Dielectric Properties of Bismuth Germanate Glass-Ceramics

Bismuth germanate composites containing Bi2GeO5-Bi4Ge3O12 phases were prepared by glass ceramic method and sintering techniques. The existences of three bismuth germanate crystals of Bi2GeO5, Bi4Ge3O12 and BiBO3 were found in XRD patterns. The amount of each phase depended mostly on the sintering temperature where the Bi4Ge3O12 phase was found to increase with increasing sintering temperature. The mixing of round and pyramidal shape crystals was observed in the sample sintered at 650°C. This gave rise to the improvement in its dielectric properties where the ϵr was found to increase from ∼78 to ∼395 for the sample sintered at 500°C and 650°C, respectively. Moreover, the tanδ was found to decrease greatly with increasing sintering temperature. Thus, this Bi2GeO5-Bi4Ge3O12 composite may be considered as a promising candidate of microwave dielectric materials.

Effect of CeO2 on the crystallization behavior and magnetic properties of Zn-ferrite glass ceramics

In this study CeO2 was added to Zn-ferrite glass ceramic. Glass–ceramic with a composition (Fe2O3–ZnO–SiO2–CaO–CeO2) was prepared by a glass ceramic method and the effect of partial replacement of 10, 20 and 30mol.% of Fe2O3 with CeO2 was studied. Based on the obtained results, it can be observed that the solubility limit of Ce3+ ions in this Ce-substituted glass ceramic, in an ordinary atmosphere, was approximately 10%. When the Ce3+ content exceeded the solution limit for Zn-ferrite glass ceramic, a foreign CeO2 phase was residual in the glass ceramic, which led to impurity in the final materials. An excessive addition of CeO2 (20% and 30%) reduced the remanent magnetization and the saturation magnetization, opposite to what occurs with a small addition of CeO2 (10%). Consequently, the addition of CeO2 into the Zn-ferrite glass ceramic material should be controlled carefully.

The Effect of PbSe Addition on the Mechanical Properties of Bi-2212 Superconductors

The effects of PbSe addition and heat treatment on the structure and mechanical properties of Bi-2212 superconductors are analyzed. Glass ceramic method is used to produce PbSe added samples. The mechanical properties are derived using Vickers microhardness measurement results. Well known analysis methods like Meyer’s law, PSR (Proportional Sample Resistance) Model, EDP (Elastic/Plastic Deformation Model), Hays-Kendall approach and IIC (Indentation-Induced Cracking Model) are used to calculate load independent microhardness values of the samples. HK approach produces successful results for the samples A, E, F, G and H indicating ISE (Indentation Size Effect) behavior. The IIC model successfully explains RISE (Reverse Indentation Size Effect) behavior for the samples B, C and D. RISE behavior is observed only for the samples where the plastic deformation is dominant. ISE behavior is observed for the samples where both elastic and plastic deformation are produced. The results of XRD and SEM analysis show improvement with PbSe addition in the crystal structures and surface morphologies of superconducting samples.

Effect of Vanadium-Titanium Co-doping on the BPSCCO Superconductor

We have produced the (BiPb)2V x Sr2Ca3Cu4−y Ti y O12+δ compounds for x=0.05 and y=0, 0.05, 0.10 and 0.20 by glass-ceramic method. The effects of vanadium adding and Ti doping on the structure have been investigated by electrical resistance, scanning electron micrographs (SEM), XRD patterns and magnetic hysteresis loop measurements. It has been found that the high-T c superconducting phase, (2223), is formed in the samples annealed at 845 °C for 185, with concentration x=y=0.05. However, with increasing Ti doping the (2223) phase transforms into the (2212) phase. We have observed no superconducting properties for x=0.05 and y=0.20 compound. It has completely transformed to semiconductor. In addition, the critical current densities (J c), calculated from the hysteresis loop measurements by using Bean’s critical state model are obtained for the samples in the same doping range. Our data have indicated that J c decreases with increasing temperature and Ti concentration.

Hexaferrite submicron and nanoparticles with variable size and shape via glass-ceramic route

Strontium hexaferrite single domain particles embedded in the borate matrix were synthesized by the glass-ceramic method. The composites exhibit various morphologies depending on the initial glass composition and the thermal treatment conditions. The obtained materials contain magnetic particles with the average size ranging from tens to hundreds nanometers and with the magnetic properties changing from superparamagnetic to hard magnetic with record-high coercivities exceeding 10 kOe.

In Vitro Bioactivity Assessment of Ceramics in the SiO<sub>2</sub>–CaO–MgO System

Both solid-state reaction and glass-ceramic methods are used to obtain bioactive materials (CaSiO3) with different concentrations of MgO (6, 8, and 10 wt %) on the basis of the stoichiometric composition of CaO·SiO2. The in vitro bioactivity assessment is performed by immersing samples in SBF (simulated body fluids) for different periods of time. The analysis of the materials before immersion indicates the presence of different phases (akermanite, wollastonite and diopside) in the materials obtained by the solid state reaction method. It is possible to obtain wollastonite with incorporation of magnesium in its structure ((Ca, Mg)·SiO6) by the glass-ceramic method. The results obtained after immersing the samples in SBF indicate that a Ca, P-rich layer is formed on all the materials tested, even in those containing a high quantity of MgO. However, the layer formed in the MgO-free CaSiO3 ceramic is thicker than that formed in the MgO-containing materials.

Effect of Mo substitution on the structural and transport properties of Bi 2Sr 2Ca 2Cu 3− xMo xO 10+ y system

The glass samples with nominal composition of Bi 2Sr 2Ca 2Cu 3− x Mo x O 10+ y , where x = 0.5, 1.0, 1.5 and 2.0, were prepared using glass-ceramic method. The structural, thermal and transport properties of the samples prepared were investigated. After x = 1.0 substitution level glass formation was diminished and crystallized samples were obtained. XRD and SEM investigations showed that all the samples have multiphase and complex crystal structures. Crystallization activation energy, E a, was calculated using both Augis–Bennett method and Kissinger method. Calculated Avrami parameter, n, suggested that diffusion-controlled growth mechanism exists for all samples. It was seen that T c and T 0 decreased as the Mo concentration is increased. The normal state resistance and hole concentration increases by increasing the Mo level. Negative thermoelectric power above T c and positive thermoelectric power below T 0 were found for all the substitution cases and heat treatment cycles indicating that both type of carriers (holes and electrons) are present for all the samples prepared. We analyzed the thermoelectric power as a function of temperature with “Two band model with linear T term” and “Xin's two band model”. Thermal conductivity κ( T) measurements were carried out between 300 and 30 K. The magnitude of κ was suppressed when Mo was increased in the BSCCO system. Results obtained give an evidence for increase of the quasi-particle mean free path.

Preparation of Y‐type Barium Hexaferrite by the Glass–Ceramic Method

Y‐type Ba‐hexaferrites (Ba2Zn2Fe12O22), which have been identified as electromagnetic wave absorbers, were prepared by the glass–ceramic method. Glasses with the composition 0.1ZnO·0.9(xB2O3·yBaO·(1−x−y)Fe2O3) were prepared, and the precipitation of Y‐type Ba‐hexaferrite from the glass matrix was investigated. Y‐type Ba‐hexaferrite were precipitated by heating glass specimens with roughly the composition 0.1ZnO·0.9(0.2B2O3·0.5BaO·0.3Fe2O3) at temperatures above about 1073 K. The lower temperature limit at which single‐phase Y‐type powder was obtained after leaching with a dilute HCl solution was about 1093 K. The low‐temperature formation of Y‐type Ba‐hexaferrite was linked to the generation of a liquid phase. The shape of Y‐type crystals depended strongly on the heating temperature and changed from a plate‐like hexagon to a complex polyhedron with increasing heating temperature.

Effect of preparation conditions on superconducting properties of (Bi,Pb)‐Sr‐Ca‐Cu‐O glass‐ceramics

In this work we present the influence of annealing conditions on superconducting properties of (Bi,Pb)-Sr-Ca-Cu-O high temperature superconductors prepared by the glass-ceramic method. Superconducting (Bi,Pb)-Sr-Ca-Cu-O samples were obtained by annealing of amorphous (Bi0.8Pb0.2)4Sr3Ca3Cu4Ox at temperatures between 750 °C and 865 °C for various time intervals between 1 minute and 43 hours. The electrical and superconducting properties of the material change during annealing because oxide superconductors belonging to the bismuth family (Bi,Pb)2Sr2CuOx (2201), (Bi,Pb)2Sr2CaCu2Ox (2212) and (Bi,Pb)2Sr2Ca2Cu3Ox (2223) crystallise forming a granular metal and superconductor. Low temperature resistivity and magnetic measurements show that during the growth of crystalline phases superconducting properties develop rapidly. Measurements of magnetisation reveal that isolated grains of superconducting 2212 phase crystallise already in the first minute of annealing at 850 °C. Further development of superconducting phases leads to subsequent improvement of superconducting properties. Properties of the material (e.g. critical temperature, critical current) and kinetics of changes depend on the temperature and time of annealing. The highest critical current densities were obtained for samples annealed at 850 °C for 43 hours. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)