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The influence of barium oxide on glazes in the SiO 2 -Al 2 O 3 -CaO-MgO-K 2 O system was investigated. Samples were prepared with 0, 2.5, 5 and 7.5 wt% of barium oxide added to this system. The glazes were fired at 1240 °C and the structure and surface properties were determined. Qualitative and quantitative analyses of phase composition, surface properties, structural mid-infrared analysis, and microstructure were performed. Diopside was detected in all glazes as the MgO content was higher than 2.5 wt%. Hyalophane crystals were observed when the BaO content increased to 5 wt%. Mid-infrared studies showed that the appearance of crystalline phases ordered the structure of the glazes; on the other hand, the amorphous phase increased its disorder related to the higher amount of modifying barium cations. The addition of barium oxide did not significantly affect the color of the surface but caused an increase in roughness due to surface crystallization. The microhardness increased with an increased amount of barium in the amorphous phase. [ABSTRACT FROM AUTHOR]

The impacts of the Bi 2 O 3 /BaO ratio on the microstructure, optical, ligand field, and radiation shielding features of BSrFeBaBi glass matrix. The Bi 2 O 3 content of the BSrFeBaBi glasses was increased from 0 to 20 mol%. The density increased from 3.77 g / cm 3 to 5.00 g / cm 3 and the molar volume increased from 24.74 cm 3 / mol to 31.17 cm 3 / mol with increasing Bi 2 O 3 /BaO ratio. The optical analysis confirmed that the transparency of BSrFeBaBi glasses in the visible region is high. Moreover, the presence of Fe cations in the octahedral coordination (FeO 6 units) was confirmed. Furthermore, the fundamental absorption edge of BSrFeBaBi glasses shifts towards lower energies with additional Bi 2 O 3 /BaO concentrations, confirming the reduced behavior of the optical band gap. Also, ligand field splitting values decreased while Racah parameters increased. The obtained results demonstrate a tendency of the bonds between the Fe ions and their surroundings towards higher degree of ionic nature. Furthermore, the Bi 2 O 3 /BaO ratio demonstrated an enhanced radiation shielding behavior. Finally, BSrFeBaBi glasses exhibit favorable attributes for use in the radiation shielding domain due to their efficient radiation shielding features and transparency. [ABSTRACT FROM AUTHOR]

Silica-aluminum borates (SiO 2 -R 2 O 3 -R 2 O-RO-ZrO 2 system) with La 2 O 3 replacing BaO were preparing using the conventional melt quenching process. The impact of substituting BaO with La 2 O 3 on the glass structure was examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman. The density, thermal properties, alkali resistance and dielectric properties of the glasses were measured and compared using Archimedes, Differential Scanning Circuit (DSC), Thermal Expansion Calorimetry (TEC), Weight Reduction and Impedance Spectroscopy. The viscosity of the glass system was calculated from the thermal properties and discussed in comparison with the wetting angle at 1000 °C. The results showed that the glass does not undergo precipitation. With the increase of La 2 O 3 to BaO substitution, the Q4 in the glass network structure transforms to Q0+Q1 and Q2, causing depolymeriation of the glass structure. This results in an increase in the density of the glass, as well as an increase and subsequent decrease in the thermal expansion coefficient. Additionally, the glass transition temperature and glass softening temperature decrease and then increase, which was due to the high field strength of La3+. When substituting 5 wt% of BaO with La 2 O 3 , The glass displayed the lowest dielectric constant and dielectric loss, along with the best alkali resistance. Viscosity calculations showed that the viscosity gradually increases at 1000 °C with the increase of La 2 O 3 substitution, which was consistent with the wettability results. The glass components in the 0-5 wt% weight range all satisfy the iron-sealed glass wetting angle requirements. [ABSTRACT FROM AUTHOR]

In this study, pink colour development was investigated by changing systemically alkaline and alkaline earth ratios of the developed glaze. Group-1 (Na 2 O/CaO, Na 2 O/MgO, Na 2 O/BaO) and Group-2 (CaO/MgO, CaO/BaO) represent compositional variations. Group-1 has alkaline oxides with changing ratios of 0.2 mol Na 2 O and 0.6 mol CaO and 0.2 mol Na 2 O and 0.2 mol BaO, respectively. These ratios vary as 0.2 mol CaO and 0.1 mol BaO in Group-2. According to the results, the pink colour intensity was improved in the compositions with cassiterite (SnO 2) and malayaite CaSn(SiO 5) phases. In addition, bar-shaped BaO–CaO–Al 2 O 3 –SiO 2 crystals were observed in structures with high barium oxide content. It could be concluded that the pink colour development regarding the a* (redness) value may also be related to the presence of BaO–CaO–Al 2 O 3 –SiO 2 [ABSTRACT FROM AUTHOR]

Designing glass with excellent acid resistance is a prerequisite for developing high-performance terminal electrode pastes. Herein, we fabricated Y 2 O 3 doped BaO–B 2 O 3 –SiO 2 glass with excellent anti-sulfuric acid corrosion properties. The anti-corrosion mechanism of glass in acid environment was investigated by spectra and microstructure analysis. The passivating gel layer with a porous structure was formed on the glass surface during the corrosion process. The average pore diameter of the porous gel could be reduced by increasing the content of Y 2 O 3. The smaller pore size of the porous gel would considerably increase the collision frequency between solvent molecules and the pore wall, which could effectively inhibit the ion migration in the gel layer, reduce the corrosion rate, and improve the acid resistance of the glass. This study contributes to the understanding of the corrosion mechanism of the glass and provides theoretical guidance for rationally designing anti-acid corrosion glass for terminal electrode pastes. [ABSTRACT FROM AUTHOR]

The effects of substituting CaO with BaO on the crystallization and sintering behavior of bioactive glass powders in the SiO 2 –B 2 O 3 –Al 2 O 3 –CaO–Na 2 O–P 2 O 5 system were observed during the Spark Plasma Sintering (SPS) process. The outcome of thermal analysis confirmed the surface crystallization mechanism for the glasses. It was revealed that the replacement of 3.3 mol.% BaO accelerated the crystallization kinetics of glass powder while replacing 9.0 mol.% BaO prevented crystallization. The X-ray diffraction results showed that upon increasing BaO replacement, pseudo-wollastonite phase was crystalized instead of wollastonite. Additionally, by replacing 3.3 and 9.0 mol.% of BaO, the beginning temperature of the sintering process was reduced from 450 °C to 440 and 425 °C, respectively. The relative densities of the sintered bodies containing 0.0% and 3.3 mol.% of BaO were 99.95 and 99.27, respectively. Substitution of 9.0 mol.% BaO resulted in a completely amorphous and full-dense sample (relative density of 100%). The in vitro apatite formation ability and osteoblastic cell behavior of the sintered bodies were evaluated. The substitution of BaO for CaO restricted the glass apatite formation ability; however, no cytotoxic effect was found. For all SPS-sintered glasses, an appropriate cell-surface interaction was observed, confirming good cell supporting behavior of produced bodies. Moreover, the radiopacity features were assessed and the higher radiopacity was achieved for Ba-containing bodies. [ABSTRACT FROM AUTHOR]

In this study, the effect of replacing CaO by BaO on mechanical properties, bioactivity, and cell adhesion of SiO 2 –B 2 O 3 –Al 2 O 3 –P 2 O 5 –CaO–Na 2 O based glass was investigated. Mechanical characterization, depth-sensing nano-indentation, and surface micro-indentation techniques were employed to determine the fracture toughness (K IC). The surface was photographed after micro-indentation effect using scanning electron microscopy. In vitro responses of the compounds of tris-buffered SBF solution were studied from different points of view: (i) morphology and elemental surface analysis using field emission electron microscopy equipped with energy dispersive spectroscopy; (ii) change in bonds using Raman spectroscopy; and (iii) ICP method for detecting the change in ion chemistry of SBF solution. The cell adhesion behavior was qualitatively evaluated by examining the morphology and attachment of mouse fibroblastic cells to the surface of the glasses. The results demonstrated that with the replacement of barium oxide, the hardness of the base glass increased, while the level of fracture toughness was maintained. In addition, in vitro bioactivity of barium oxide-containing glass was reduced compared to the base glass. However, structural dissolution and formation of calcium phosphate layers on their surfaces were also confirmed. The results showed that BaO-incorporated glasses had adequate cell propagation and proliferation, hence enjoying appropriate biocompatibility for use in coating applications. [ABSTRACT FROM AUTHOR]

The present study replaced 3.30 and 9.00 mol.% BaO for CaO in a SiO 2 –B 2 O 3 –Al 2 O 3 –CaO–Na 2 O–P 2 O 5 bioactive glass system used for implant coating applications. Variations of the glass structure, thermal properties, cytotoxicity, and radiopacity of glasses were studied. As demonstrated by the results, upon adding barium oxide to the glass structure, the weight density increased significantly, while a slight decrease in oxygen density was determined. Introducing barium oxide into glass composition did not cause any considerable change in the spectra of FTIR and Raman. It was demonstrated that the amount of bridging oxygen in the glass structure remained quite unaffected. The hot stage microscopy evaluations revealed further shrinkage of barium-containing frits due to lower viscosity and hence, higher viscous flow of these glasses. By substituting barium oxide for calcium oxide and increasing its concentration, the glass transition temperature (T g) and the dilatometric softening temperature (T d) decreased, while the thermal expansion coefficient increased. Moreover, upon substituting 9 mol.% barium oxide for calcium oxide, a 30 °C reduction in maximum sintering temperature (T ms) of the glass was obtained, whereas the shrinkage rate was increased 1.7 times. It was indicated that the sintering process of barium-incorporated glasses would easily proceed without any phase crystallization. The barium-incorporated glasses exhibited more radiopacity. Additionally, no cytotoxic effect was caused by the substitution, and the Ba-containing glasses could be used for biomedical applications and implant coating as well. [ABSTRACT FROM AUTHOR]

In this work structural and luminescence properties of gallo-germanate glasses were investigated. The mentioned glass system was modified with barium and antimony oxides and doped with Eu3+ ions. The starting glass consisted of barium oxide as a modifier which was then gradually replaced by antimony oxide to form six glass samples. The gallo-germanate glass as a low-phonon host for RE (Rare Earths) ions is a promising material for optoelectronics. However, luminescence properties closely depend on material composition. For this reason, structural changes in studied materials were induced by changing its chemical composition and the luminescence properties were tested. The FT-IR (Fourier-Transform Infrared Spectroscopy) and the Raman spectra of studied glasses illustrate the tendency to increasing quantity of bridging oxygen connecting germanium ions and decreasing quantity of non-bridging oxygen along with antimony oxide addition. Simultaneously the BP (Boson Peak) measurements and emission spectra of Eu3+ ions show an increasing tendency to the examined glass structure ordering along with modifier oxide addition. [ABSTRACT FROM AUTHOR]

The aim of this research is to show the effect of zirconium silicate addition on sintering and physicochemical properties of glass-ceramic materials from the SiO 2 –Al 2 O 3 –Na 2 O–K 2 O–CaO–MgO–BaO system. This paper presents the results of the most important techniques used to understand the sintering process, i.e. thermal differential analysis, dilatometry measurements and hot-stage microscopy. Additionally, the following techniques have been used: X-ray diffraction (XRD) and scanning electron microscopy with a micro-analyser (SEM-EDS), and in order to obtain surface physicochemical properties: laser confocal microscopy, glossmetry, and spectrophotometry. By changing the initial composition and thermal treatment of glass-ceramic materials it is possible to shape parameters of final products which leads to obtaining a great variety of applications. [ABSTRACT FROM AUTHOR]

Abstract Stoichiometric 0.5 BaO·0.5 SrO·2 ZnO·2 SiO 2 glass was doped with 5 mol% Nb 2 O 5 or Ta 2 O 5. The effect of these additives on the crystallization behavior was studied using thermal analyses, X-ray diffraction, as well as scanning electron microscopy including elemental analyses. The addition of Nb 2 O 5 or Ta 2 O 5 significantly increases the glass stability enabling the preparation of crystal-free BaO·SrO·ZnO·SiO 2 glasses with almost stoichiometric composition. Besides the desired main crystal phase Ba 1-x Sr x Zn 2 Si 2 O 7 , also alkaline earth tantalates and niobates as well as Zn 2 SiO 4 are observed. The Nb-containing glass shows solely surface crystallization, whereas in the Ta-containing glass, additionally numerous barium tantalate crystals precipitate in the bulk acting as seeds for the nucleation of Ba 1-x Sr x Zn 2 Si 2 O 7. If the surface crystallized layer of Ba 1-x Sr x Zn 2 Si 2 O 7 approaches such a barium tantalate crystal or gets close to it, then the crystallization of Ba 1-x Sr x Zn 2 Si 2 O 7 is initiated. It is supposed that these nucleation processes are notably facilitated by the stresses present in these glass-ceramics. [ABSTRACT FROM AUTHOR]

Abstract The crystallization ability plays a key role in effecting thermal ability of sealing glass for intermediate temperature-solid oxide fuel cells (IT-SOFCs) to prevent fuel leakage during operation and insulate the cell stack from the external atmosphere. Herein, using differential thermal analysis (DTA) techniques, the growth mode of crystals precipitated in BaO-CaO-Al 2 O 3 -B 2 O 3 -SiO 2 (BCABS) sealing glass through the heat treatment was calculated in terms of non-isothermal crystallization kinetics for the first time. The calculated results showed that the average kinetic exponent n of the glass was approximatively 1, indicating that the crystal nucleuses became to form and further grew with one-dimensional mode from the surface inwards. Scanning electron microscope (SEM) observations clearly revealed that a large number of one-dimensional filamentous crystals have been formed on the interface between the sealing glass and the electrolyte after the heat treatment at 973 K for 100 h, which perfectly coincided with the theoretical calculations, and the glass was well combined with the electrolyte without any visible cracks or peeling at the interface. The one-dimensional growth of hexagonal BaAl 2 Si 2 O 8 crystals verified by X-ray diffraction (XRD) could effectively decelerate the decrease of thermal expansion coefficient of glass to ensure enhance the thermo-stability of the BCABS sealing glass for IT-SOFC. [ABSTRACT FROM AUTHOR]

A glass from the system BaO-SrO-ZnO-Al 2 O 3 -SiO 2 was synthesized and the crystallization behavior was studied using differential scanning calorimetry, X-ray diffraction, and scanning and transmission electron microscopy. The main phase precipitating is a Ba 1−x Sr x Zn 2 Si 2 O 7 solid solution with very low thermal expansion. The formation of this phase leads to a decrease of the coefficients of thermal expansion of sintered and afterwards crystallized powder compacts. The addition of Al 2 O 3 leads to the formation of another phase at the early stage of crystallization, which disappears after longer heat treatments or at elevated temperatures. For comparison, a stoichiometric powder with the composition Ba 0.5 Sr 0.5 Zn 1.9 Si 1.9 Al 0.2 O 7 was prepared via a solid-state reaction in order to verify whether or not Al 3+ -ions can be incorporated into the crystal structure. This phase does not exist as a single-phase material, which means that the addition of Al 2 O 3 leads to the formation of small concentrations of secondary phases. [ABSTRACT FROM AUTHOR]

Dense Si 3 N 4 ceramic with BaO-Al 2 O 3 -SiO 2 low temperature glass powders as sintering aids were prepared by pressureless sintering techniques at a relatively low temperature (1550 °C). Four kinds of glass powders of compositions melting at 1120 °C, 1300 °C, 1400 °C and 1500 °C, respectively, have been introduced as sintering aids. XRD results demonstrate that the BaO-Al 2 O 3 -SiO 2 glass powders reacted with BaAl 2 O 4 and converted into hexagonal celsian, which is a high-temperature phase with melting point of 1760 °C, so being beneficial to the high temperature properties of the materials. In addition, a portion of α-Si 3 N 4 transformed to rod like β-Si 3 N 4 with high aspect ratio as shown by XRD and SEM analysis. The bulk density increased with the rise of the melting temperature of the BaO-Al 2 O 3 -SiO 2 glass powders, the sample obtained with the BaO-Al 2 O 3 -SiO 2 glass powder melting at 1500 °C reaching a maximum density of 98.8%, an high flexural strength (373 MPa) and a fracture toughness (4.8 MPa m 1/2 ). [ABSTRACT FROM AUTHOR]

Boria (B 2 O 3 )-added forsterite (Mg 2 SiO 4 ) ceramics were synthesized and their properties were characterized. The addition of B 2 O 3 was aimed to produce high density forsterite ceramics at a low sintering temperature. The raw materials were purified silica sand and commercial magnesia powders. Fosterite powder was produced from a solid reaction between the raw powders at 1100 °C prior to addition of B 2 O 3 , uniaxial pressing and sintering at 1200 °C. The amount of added B 2 O 3 varied between 0%, 4%, and 8% by weight. Elemental analysis was performed by X-ray fluorescence (XRF) spectroscopy on the purified silica powder, whereas phase analyses were obtained from X-ray diffraction (XRD) data. Characterization of the ceramics included diameter shrinkage, density-porosity, thermal expansion, Vickers hardness, and dielectric constant. The results showed that the silica powder contained 98.7 at% Si with minor impurities, including 0.5 at% Ti, but the only identified crystalline phase was quartz. Further phase analysis of the ceramics showed that the addition of B 2 O 3 reduced the amount of formed forsterite and increased the amount of cristobalite, proto- and clino-enstatite (MgSiO 3 ) as well as suanite (Mg 2 B 2 O 5 ). The highest forsterite content was found in B 2 O 3 -free ceramics, approximately 88.1 wt%. Moreover, the addition of B 2 O 3 also reduced the diameter of the sample by more than 21%, resulting in a very dense ceramic with an apparent porosity of only 0.3%. The Vickers hardness significantly increased from 0.3 GPa for the B 2 O 3 -free ceramic to 10.9 GPa for the 4% B 2 O 3 sample. The dielectric constant of the B 2 O 3 -added forsterite ceramics was improved by approximately 2–6 times that of the B 2 O 3 -free ceramic, which was primarily attributed to the loss of porosity in the samples. [ABSTRACT FROM AUTHOR]

Phase evolution, dielectric properties, breakdown strength, and energy-storage performance were studied by varying K 2 O content in K 2 O-BaO-Nb 2 O 5 -SiO 2 glass-ceramics. It was found that dielectric loss with the increase of K 2 O content increases owing to the un-crystallized K 2 O into the glass network, while dielectric breakdown strength firstly increases and then decreases due to the competition between two physical mechanisms, i.e., interfacial polarization and bridging-oxygen bond broken by the non-bridging oxygen ions. With the increase of K 2 O content, energy-storage density firstly increased up to 12.06±0.69 J/cm 3 with a high breakdown strength of 1973 kV/cm, and then decreased. Also, the discharged efficiency is obtained as a high value of 92% from P-E hysteresis loops. [ABSTRACT FROM AUTHOR]

Piezoelectric properties and thermal stability of tetragonal-structured (Ba 0.838 Ca 0.162 )(Ti 0.908−x Mn x Zr 0.092 )O 3 (0.46BZT–0.54BCTMn) compositions away from morphotropic phase boundary (MPB) were investigated. The results demonstrated that the addition of small amounts of Mn did not cause a remarkable change in crystal structure, but resulted in an evident evolution in piezoelectric properties and thermal stability. Mn could induce combinatory hard and soft piezoelectric characteristics due to aliovalent substitutions and improve thermal stability. The optimal electrical properties were obtained in the modified composition at x=0.006 with piezoelectric constant d 33 =410 pC/N, planar electromechanical coupling factor k p =0.40, mechanical quality factor Q m =150, remnant polarization P r =14.1 μC/cm 2 , coercive field E c =4.44 kV/cm and a high Curie temperature T c ~99 °C, respectively. It can be expected that the improved piezoelectric material can be a promising candidate for lead-free piezoelectric applications. [ABSTRACT FROM AUTHOR]

BaO-Sm 2 O 3 -5TiO 2 (BST5) ceramics with NdAlO 3 additions of up to 15 wt% were produced with a solid state reaction method, and their structural and microwave dielectric properties were determined. Experimental results showed that NdAlO 3 neither merged nor altered the orthorhombic tungsten bronze structure of the main phase of the produced ceramics (except for a shrinkage in the crystal lattice), but it was segregated in distinct grains in the microstructure of the produced ceramics. However, the amount of NdAlO 3 strongly influenced the densification and the microstructure (i.e. grain shape and size) of the produced ceramics. Analysis of the experimental results suggests that the microstructural features can be correlated to the dielectric properties of these ceramics. Accordingly, the dielectric constant (ε r ) and the temperature coefficient of resonant frequency (τ f ) of the produced BLT5 ceramics can be tuned with the amount of NdAlO 3 additions and the sintering process parameters. The best dielectric properties were achieved for BaO-Sm 2 O 3 -5TiO 2 ceramics with 7.5% NdAlO 3 (ε r =73.22, Q×f =10,300 GHz, and τ f =−1.05 ppm/°C). [ABSTRACT FROM AUTHOR]

The effects of the addition of BaO on the sinterability, phase balance, microstructure, and mechanical properties of 8 mol% yttria-stabilized cubic zirconia (8YSZ) were investigated using scanning electron microscopy, X-ray diffraction (XRD) analyses, and micro-hardness testing. The 8YSZ powder was doped with 0–15 wt% BaO using a colloidal process. The undoped and BaO-doped 8YSZ specimens were sintered at 1550 °C for 1 h. The XRD analyses results showed that the specimens doped with up to 1 wt% BaO did not exhibit BaO-related peaks, indicating that BaO was completely solubilized in the 8YSZ matrix. However, when more than 1 wt% BaO was added, BaZrO 3 -related peaks appeared, suggesting that the overdoped BaO did not dissolve in the 8YSZ matrix but formed a secondary phase of BaZrO 3 at high temperatures. Grain size measurements showed that the grain size of 8YSZ decreased with an increase in the amount of BaO added. The decrease in the grain size was owing to the fact that the grains of BaZrO 3 , which precipitated at the grain boundaries and grain junctions of 8YSZ, increased the grain boundary cohesive resistance because of the pinning effect. This resulted in a decrease in the grain boundary mobility, and an increase in the grain boundary energy. Furthermore, while the addition of BaO to 8YSZ caused a slight decrease in the hardness of 8YSZ, the fracture toughness of 8YSZ increased from 1.64 MPa m 1/2 to 2.08 MPa m 1/2 , owing to the resulting decrease in the grain size. [ABSTRACT FROM AUTHOR]

We examined the influence of barium oxide addition on the structure and properties of SiO 2 –Al 2 O 3 –Na 2 O–K 2 O–MgO glass–ceramics. Glass–ceramics were prepared with constant SiO 2 /Al 2 O 3 and Na 2 O/K 2 O ratios of 6.5 and 1.04, respectively, and the MgO content was maintained at 10.56 wt%. The barium oxide content was set at 4 wt%, 9 wt%, and 14 wt%. The weight ratios were recalculated from the BaCO 3 added. To determine the microstructure of the glassy materials, scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS), X-ray diffraction (XRD), medium (MIR) and far infrared analysis (FIR), and Raman spectroscopy were used. Significant differences were observed in the phase composition and in the silica–alumina-oxide network of the glassy phase, which could be related to changes in the amount of barium oxide. The characteristic temperatures (beginning of sintering, sphere, half-sphere and melting), which were measured by using hot stage microscopy and dilatometry, also showed changes. [ABSTRACT FROM AUTHOR]

Crystallizing glasses in the system BaO–ZnO–NiO–SiO 2 were studied with respect to the glass formation, crystallization and thermal expansion behavior. A maximum NiO concentration of 8.8 mol% was reached in the glasses. The high thermal expansion phase BaZn 2 Si 2 O 7 and the solid solutions BaZn 2− x Ni x Si 2 O 7 derived hereof can be crystallized from the prepared glasses. The incorporation of NiO in the solid solution strongly increases the transition from the low to the high temperature phase. The introduction of NiO into the solid solution was studied, using ultraviolet–visible-near-infrared spectroscopy. Phase transitions were analyzed using in situ high-temperature X-ray diffraction and dilatometry. The introduction of NiO in the as mentioned phases led to a thermal expansion coefficient in the range from 11.1 to 17.2×10 −6 K −1 . In contrast to other crystallized sealing materials, the thermal expansion coefficient is nearly constant over a wide temperature range (25–1000 °C). Furthermore, it is shown, that the thermal expansion behavior of the multiphase glass ceramics can be predicted from the thermal expansion of the different ceramic phases. The crystallizing glass may be suitable as sealing material for components with high coefficients of thermal expansion such as ferritic stainless steels or nickel alloys. [ABSTRACT FROM AUTHOR]

BaO–CaO–Al 2 O 3 –B 2 O 3 –SiO 2 (BCAS) glass–ceramics can be used as sealant for large size planar anode-supported solid oxide fuel cells (SOFCs). BCAS glass–ceramics after heat treatment for different times were characterized by means of thermal dilatometer, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the coefficients of thermal expansion (CTE) of BCAS glass–ceramics are 11.4×10 −6 K −1 , 11.3×10 −6 K −1 and 11.2×10 −6 K −1 after heated at 750 °C for 0 h, 50 h, and 100 h, respectively. The CTE of BCAS matches that of YSZ, Ni–YSZ and the interconnection of SOFC. Needle-like barium silicate, barium calcium silicate and hexacelsian are crystallized in the BCAS glass after heat-treatment for above 50 h at 750 °C. The glass–ceramics green tape prepared by aqueous tape casting can be directly applied in sealing the cell of SOFCs with 10 cm×10 cm. The open circuit voltage (OCV) of the cell keeps 1.19 V after running for 280 h at 750 °C and thermal cycling 10 times from 750 °C to room temperature. The maximum power density is 0.42 W/cm 2 using pure H 2 as fuel and air as oxidation gas. SEM images show no cracks or pores exist in the interface of BCAS glass–ceramics and the cell. [ABSTRACT FROM AUTHOR]

This article focused on effect of the content of barium oxide on microstructure of the glass–ceramic materials based on the system SiO 2 –Al 2 O 3 –Na 2 O–K 2 O–CaO. The following characterisation techniques have been used: X-ray diffraction (XRD), scanning electron microscopy with micro-analyser (SEM–EDS), mid-infrared analysis (MIR), far-infrared analysis (FIR) and Raman Spectroscopy. Significant differences were observed in microstructure of silica–alumina network of glassy phase and phase composition related to changes in the amount of the barium oxide additive. Discussed results are part of a larger project implemented under the PBS Applied Research Programme, in order to determine the compositions of glass–ceramic materials with potential application as a chemically resistant hard coatings or/and resistant to thermal shock or as construction materials. [ABSTRACT FROM AUTHOR]

A new type of lead-free piezoelectric ceramics (1− x )Ba(Zr 0.15 Ti 0.85 )O 3 – x (Ba 0.8 Sr 0.2 )TiO 3 (abbreviated as BZT– x BST or BSZT) were designed and prepared using the traditional solid-state reaction technique. The polymorphic phase transition (PPT) from rhombohedral to tetragonal phase ( R – T ) was adjusted to room temperature through modifying the proportion of BZT and BST terminals. A high piezoelectric coefficient d 33 =450 pC/N and a high dielectric permittivity ε r =4070 were simultaneously demonstrated for the BSZT ceramic samples with x =0.70, indicating that the BSZT ceramics are promising candidates for lead-free piezoelectric applications. [ABSTRACT FROM AUTHOR]

Effects of Zr-substitution on the structure, microstructure and microwave dielectric properties of Ba(Ni 1/3 Nb 2/3 )O 3 ceramics have been investigated. A small amount of Zr-substitution facilitates the densification of Ba(Ni 1/3 Nb 2/3 )O 3 ceramics. Within x ≤0.05, the densification temperature decreases with increasing x in Ba[(Ni 1/3 Nb 2/3 ) 1− x Zr x ]O 3 , while it turns to increase for x >0.05. With increasing x , the grains become more homogeneous and closely contacted, and significantly increase in size for x =0.15–0.20. The B-site cations 1:2 ordering is destroyed by Zr-substitution, and only stabilizes for x ≤0.04. B-site cations 1:1 ordering starts to form in x =0.04, and the 1:1 ordering degree first increases and then decreases with increasing x. Qf value decreases slightly in x =0.01 and then increases monotonously with x increasing from 0.02 to 0.20. The destroyed 1:2 ordering structure is responsible for the decreased Qf value in x =0.01, while the improved grain configuration dominates the increase of Qf value for x =0.02–0.20. The dielectric constant ε r increases monotonously with increasing x , due to the higher polarizability of Zr ion than the average value of Ni/Nb ions. The temperature coefficient of resonant frequency τ f shifts from negative to positive through zero with increasing x , which is ascribed to the highly positive τ f value of the end member BaZrO 3 . The significant improvement of microwave dielectric properties has been achieved for x =0.10, higher ε r , higher Qf as well as near zero τ f value have been obtained: ε r =31.8, Qf =36,100 GHz, τ f =7.8 ppm/°C. [ABSTRACT FROM AUTHOR]

SiO 2 –B 2 O 3 –CaO vitrified bonds are widely used in the fabrication of diamond abrasive tools. The structures and properties of SiO 2 –B 2 O 3 –CaO vitrified bonds with low sintering temperatures and high strength were investigated. Their structures were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FTIR). The bending strength, Rockwell hardness, and thermal expansion coefficients were tested at meantime. The interfacial bonding state between the diamond grains and an optimized 4# vitrified bond was observed by scanning electron microscopy (SEM). The results showed that the thermal expansion coefficients of the varied vitrified bond samples approximated to 7.0×10 −6 °C −1 , the highest bending strength attained was 114 MPa, and the highest Rockwell hardness achieved was 60 HRB. The bending strength displayed regular changes with rising sintering temperatures as did the hardness values. The 4# vitrified bond efficiently wetted diamond grains, enhancing the interfacial bonding strength. [ABSTRACT FROM AUTHOR]

Abstract: We present a topochemical route for the synthesis of BaFe12O19 nanorods by using hydrothermal synthesized mixture of α-FeOOH nanowires and BaCO3 as precursors. The α-FeOOH nanowires and in-situ formed BaCO3 transformed to BaFe12O19 nanorods by a two-step annealing process. The crystal structure and morphology changes of the products with annealing temperatures were investigated. BaFe12O19 nanorods with diameters of about 250nm and lengths of about 1μm were obtained at annealing temperature of 1000°C. A comparison of magnetic properties between BaFe12O19 nanorods and granules was performed and discussed. [Copyright &y& Elsevier]

Abstract: Microwave dielectric properties of (1− x)BaZn2Ti4O11–xBaNd2Ti4O12 (x =0–1.0) ceramics were investigated by the solid-state reaction with the purpose of finding a microwave ceramics with high dielectric constant (ɛ r), high quality factor (Q × f) and low temperature coefficient of resonant frequency (τ f). A two phase system BaZn2Ti4O11–BaNd2Ti4O12 was formed and SEM photographs show equiaxed BaZn2Ti4O11 grains and columnar BaNd2Ti4O12 grains. The microwave dielectric properties were strongly determined by the chemical composition. As increasing x from 0 to 1.0, the phase composition varied from pure BaZn2Ti4O11, to the two phase system BaZn2Ti4O11–BaNd2Ti4O12 and then to pure BaNd2Ti4O12. Therefore, the ɛ r raised from 29.1 to 82.0 and the Q × f values decreased from 54,630GHz to 8110GHz, and the τ f values increased from −29ppm/°C to 94ppm/°C. 0.8BaZn2Ti4O11–0.2BaNd2Ti4O12 ceramics sintered at 1250°C for 2.5h had ɛ r =39.1, Q × f =37,850GHz and τ f =−9ppm/°C. [Copyright &y& Elsevier]

Abstract: The influence of barium oxide, heat treatment time and temperature on the crystallization, microstructure and mechanical behavior of the system Ba x ·K1−2x ·Mg3·Al·Si3O10·F2 (where x =0.0, 0.3 and 0.5) was investigated in order to develop novel, high strength and machinable glass–ceramics. Three glasses were prepared and characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscope (SEM) techniques and some mechanical testing methods. The crystallization kinetics of glass–ceramics was also studied. Activation energy and Avrami exponent calculated for the crystallization peak temperature (T p) of three different glass batches. The Vickers hardness decreased slightly on formation of the potassium fluorophlogopite and barium fluorophlogopite phases, but decreased significantly on formation of an interconnected ‘house of cards’ microstructure. [Copyright &y& Elsevier]

An organic-inorganic 0–3 nanocomposites, in which nanoparticles (0-dimensional) are embedded in a 3-dimensionally connected polymer matrix, rapidly emerged for a number of advanced engineering applications. The nanocomposites with enhanced dielectric performance is realized by employing Ba(Fe 0.5 Ta 0.5 )O 3 (BFT) with giant dielectric constant ( ε′ ) as a ceramic filler and poly(vinylidene fluoride) (PVDF) as a polymer matrix. The dense nanocomposites use the hot-press process, which can eliminate the porosity. Experimental data shows that dielectric constant of the nanocomposites with 60 vol% of BFT can reach 97 at 100 Hz, which is attributed to the individual dielectric constant of BFT and PVDF, and enhanced interfacial polarization. Meanwhile, the soft percolation regime is found at the volume filling fractions of BFT between 0.2 and 0.3, which also plays an important role in enhanced dielectric constant. Different theoretical models are applied to predict the dielectric constants of the nanocomposites. Furthermore, the introduction of BFT nanoparticles improves the temperature stability of dielectric constant in the temperature range from 20 °C to 120 °C. [ABSTRACT FROM AUTHOR]

In the present study, Ce-doped Ba(Ti 0.99 Mn 0.01 )O 3 (BT-1Mn-xCe, x= 2, 5, 8, 10 mol%) lead-free ceramics were prepared by using the conventional solid state method. The morphologies, phase structures, dielectric properties and aging behaviors of the Ce-doped Ba(Ti 0.99 Mn 0.01 Ce)O 3 samples were investigated to reveal the effects of cerium doping on their aging behaviors. The results show that all the samples have a single perovskite structure. With the cerium content increasing, the two transition temperatures (the Curie temperature T C and the tetragonal to orthorhombic structural transition temperature T 1 ) gradually merged into one. Moreover, the dielectric permittivity shows a broad and diffuse peak with the cerium content increasing. The measurement of polarization-electric field (P-E) hysteresis loops shows a more and more obvious constricted tendency with the aging time increasing. For BT-1Mn-2Ce sample, the aging is fast and then slows down to a stable condition. While for x≥5 mol% samples, the aging is slow and then fast and does not reach a stable condition during the measured time. The relation between the aging rate and crystal structure was discussed. This may help us on controlling the aging behavior of other lead-free ferroelectric ceramics. [ABSTRACT FROM AUTHOR]

The (BaO, Na 2 O)–Nb 2 O 5 –SiO 2 glass-ceramics with various amounts of La 2 O 3 addition, were fabricated through melt casting followed by controlled crystallization. The effect of La 2 O 3 addition on the phase transition, microstructure, and dielectric properties for (BaO, Na 2 O)–Nb 2 O 5 –SiO 2 glass-ceramics was investigated. With the addition of La 2 O 3 , the dielectric constant and the breakdown strength for the glass-ceramics were drastically improved, which resulted in the improvement of the discharged property. The maximum energy-storage density of 8.4 J/cm 3 was achieved in the niobate glass-ceramics with 0.5% La 2 O 3 addition, indicating that the glass-ceramic with this composition is a promising dielectric material for high energy storage density capacitors. [ABSTRACT FROM AUTHOR]

Abstract: BaTi4O9 (BT4) microwave dielectric ceramics using a copper electrode and containing 10wt% BaO–ZnO–B2O3–SiO2 (BZBS) glass frit were sintered under reducing atmosphere at 950°C and were investigated on the phase evolutions, microstructures and dielectric properties of BT4 with various BaO/SiO2 and ZnO/SiO2 ratios of BZBS glasses. Experimental results show that the BaO/SiO2 ratio contributes to wettability of glass with BaTi4O9 ceramics, and ZnO/SiO2 ratio determines the densification of BaTi4O9 ceramics. The different Ba–Ti–O and Ba–Cu–O phases with various Ba/Ti and Ba/Cu ratios can be attributed to the contents of BaO in glass. Ba4Ti13O30 and Ba2Cu3O5+X may form when BaO contents are too high, and inducing copper diffusion due to the reactions of BaO and Cu, accompanying with degrading of the dielectric characteristics. If the ZnO contents of BZBS glasses were raised, a little bit of ZnSiO3 and Ba2Cu3O5+X phases appear without Cu diffusion due to non-reaction of ZnO and CuO. The high ZnO/SiO2 ratio of glass reveals the lower softening point, indicating that the high ZnO glass could enhance the density and therefore increase the dielectric constant and quality factor. [Copyright &y& Elsevier]