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Multifunctional radiation shielding materials are important for the development of miniaturised nuclear reactors. Bi6B10+2xO24+3x (x = − 2, − 1,0,1,2) compounds were economically and conveniently synthesised by using a solid-state sintering reaction of bismuth oxide and boric acid. The effects of liquid phase boron oxide migration due to sintering temperature and boric acid content on the microscopic morphology, crystalline phase composition and macroscopic properties of the samples were systematically investigated. And the studies highlight that when the content of boric acid particles increases, the nucleation and growth of bismuth borate is accelerated, which promotes the sintering of the ceramic and have a positive effect on improving the physical properties of materials. The ceramic with x = 1 exhibited the highest cold elastic modulus (28.41 GPa), cold flexural strength (18.55 MPa) and room temperature thermal conductivity (0.3420 W/(m·K)). Radiation shielding tests showed neutron and gamma shielding of 63.7% and 39% for the ceramic with x = 1 when the sample thickness was 1.5 cm. Thus, based on the information gathered from our research, Bi6B10+2xO24+3x (x = − 2, − 1,0,1,2) ceramics were expected to be designed as an integrated nuclear reactor shielding/insulation material. [ABSTRACT FROM AUTHOR]

Bi 3 B 5+ x O 12+3 x /2 (x = 0∼6) compounds were fabricated by a conventional solid-state reaction method. The microwave dielectric properties, sintering behaviour, crystal structure, and phase evolution of the ceramics were investigated. All samples densified at ultra-low temperatures (575∼700 °C). As x increased, the phase composition of the ceramics gradually changed from mixed Bi 4 B 2 O 9 and Bi 3 B 5 O 12 phases to a single Bi 6 B 10 O 24 phase. The ceramic with x = 4 exhibited the best microwave dielectric properties of ε r = 12.14, Q × f = 14,800 GHz, and τ ƒ = −72 ppm/°C at 625 °C. The microwave dielectric properties deteriorated as x increased further. Moreover, the ceramics were proven to cofire with Al and Ag, indicating that they are candidates for ultra-low-temperature cofired ceramic devices. [ABSTRACT FROM AUTHOR]

Bismuth-borate glass braze (Bi25) with low melting point was utilized to braze magnesium titanate ceramic (MTC) in this work. The interfacial reaction between MTC and bismuth-borate glass braze made a well brazing possible. First, the Zn atoms from the glass seam substituted Mg atoms from MTC forming the phase (Zn,Mg) 2 TiO 4 of lamellar morphology, which reacted with [BiO 6 ] (or [BiO 3 ]) from glass seam and then generated Bi 4 Ti 3 O 12 of granular and sheet-like morphologies. The Mg2+ deriving from the reactions above reacted with [SiO 4 ] unit from glass seam and generated Mg(SiO 3) of granular and stripe-like morphologies. The shear strength increased first and then decreased with the increase of brazing temperature constantly. It reached a maximum value of 72 MPa at 725 °C. The dielectric loss tangent of joints always tended to zero at high frequency, and the dielectric constant of joints brazed at 750 °C was closest to that of base MTC itself. [ABSTRACT FROM AUTHOR]

The first silver bismuth borate, AgBi2B5O11 (silver dibismuth pentaborate), has been prepared via glass crystallization in the Ag2O–Bi2O3–B2O3 system and characterized by single‐crystal X‐ray diffraction. Its structure is derived from that of centrosymmetric Bi3B5O12 by ordered substitution of one Bi3+ ion for Ag+, which results in the disappearance of the mirror plane and inversion centre. Second harmonic generation (SHG) measurements confirm the acentric crystal structure. It is formed by [Bi2B5O11]∞ layers stretched along c and comprised of vertex‐sharing B5O10 and BiO3 groups which incorporate the Ag+ cations. The new compound was characterized by thermal analysis, high‐temperature powder X‐ray diffraction, and vibrational and UV–Vis–NIR (near infrared) spectroscopy. Its thermal expansion is strongly anisotropic due to the presence of rigid B5O10 groups aligned in a parallel manner. The minimal value is observed along their axis [parallel to c, αc = 3.1 (1) × 10−6 K−1], while maximal values are observed in the ab plane [αa = 20.4 (2) and αb = 7.8 (2) × 10−6 K−1]. Upon heating, AgBi2B5O11 starts to decay above 684 K due to partial reduction of silver; incongruent melting is observed at 861 K. According to density functional theory (DFT) band‐structure calculations, the new compound is a semiconductor with an indirect energy gap of 3.57 eV, which agrees with the experimental data (absorption onset at 380 nm). [ABSTRACT FROM AUTHOR]

The first silver bismuth borate, AgBi2B5O11 (silver dibismuth pentaborate), has been prepared via glass crystallization in the Ag2O–Bi2O3–B2O3 system and characterized by single‐crystal X‐ray diffraction. Its structure is derived from that of centrosymmetric Bi3B5O12 by ordered substitution of one Bi3+ ion for Ag+, which results in the disappearance of the mirror plane and inversion centre. Second harmonic generation (SHG) measurements confirm the acentric crystal structure. It is formed by [Bi2B5O11]∞ layers stretched along c and comprised of vertex‐sharing B5O10 and BiO3 groups which incorporate the Ag+ cations. The new compound was characterized by thermal analysis, high‐temperature powder X‐ray diffraction, and vibrational and UV–Vis–NIR (near infrared) spectroscopy. Its thermal expansion is strongly anisotropic due to the presence of rigid B5O10 groups aligned in a parallel manner. The minimal value is observed along their axis [parallel to c, αc = 3.1 (1) × 10−6 K−1], while maximal values are observed in the ab plane [αa = 20.4 (2) and αb = 7.8 (2) × 10−6 K−1]. Upon heating, AgBi2B5O11 starts to decay above 684 K due to partial reduction of silver; incongruent melting is observed at 861 K. According to density functional theory (DFT) band‐structure calculations, the new compound is a semiconductor with an indirect energy gap of 3.57 eV, which agrees with the experimental data (absorption onset at 380 nm). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • With the help of first-principles calculations, we propose a new type of two dimensional (2D) topological insulator BiB with bilayer hexagonal lattice. • The spin-orbit coupling will turn this 2D material into topological insulators with nontrivial edge states. • Surprisingly, two mechanisms, including crystal field and strong SOC, induce two band inversions and manipulate the low energy electronic states simultaneously. • The BiB provides a fertile platform for studying the interactions between the two different mechanisms in the same topological insulator. Abstract With the help of first-principles calculations, we propose a new type of two dimensional (2D) topological insulator BiB with bilayer hexagonal lattice. Its dynamic stability was confirmed by the phonon spectrum. When spin-orbit coupling (SOC) effect is not considered, the low energy electronic states around the Fermi level show metallic characteristics. However, the SOC will induce a global band gap and turn this 2D material into topological insulators with nontrivial edge states. Surprisingly, two mechanisms, including crystal field and strong SOC, induce two band inversions and manipulate the low energy electronic states simultaneously. The BiB provides a fertile platform for studying the interactions between the two different mechanisms in the same topological insulator. Moreover, the sizable global nontrivial band gap indicates its high working temperature. [ABSTRACT FROM AUTHOR]

Abstract Interaction of 10ZnO-5Na 2 O-10Bi 2 O 3 –74.3B 2 O 3 -0.7Eu 2 O 3 glasses exposed to high dose gamma rays were investigated using XRD, FTIR, absorption, photoluminescence followed by thermally and optically stimulated luminescence studies. XRD analysis confirmed the amorphous nature of glasses post-irradiation. Variation in FTIR spectra revealed, structural deformation of borate groups as a result of high dose gamma irradiation. Enhanced glass absorbance and red shift in absorption edge were observed with the increase in gamma dose. Further, radiation-induced absorption coefficient confirmed the trapped charges in the forbidden energy gap supported by Tauc's plot and Urbach energy. Photoluminescence (PL) study demonstrated quenching of luminescence intensity at higher gamma doses. Lifetime of metastable 5D 0 state of Eu3+ ions were estimated by the decay curves and color purity was calculated using 1931 CIE chromaticity coordinates (x,y). Thermally and optically stimulated luminescence studies reassured the existence of charges in trap centers due to irradiation. TL glow curve exhibited two broad emission peaks with the corresponding temperature being at 490 K and 625 K. Distinct TL peaks of the material and their kinetic parameters (E, S, τ and b) were determined via Computerized Glow Curve Deconvolution (CGCD) method. Linear behaviour obtained through the dose response of the glass (0.25–3 kGy) proved their suitability for dosimetric application in the food irradiation zones in addition to red LEDs (< 1 kGy). Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Abstract Glasses in the series, 49B 2 O 3 -25SiO 2 -(26-x)Bi 2 O 3 -xBaO (with x between 2 and 8 wt%) are considered for radiation shielding applications based on the gamma-ray half-value layer (HVL) and mass neutron removal cross-section. Theoretical data for the calculation of the HVL is obtained from the NIST XCOM software. The calculated HVL shows good correspondence to the experimentally determined values. The mass neutron removal cross-section and the half-value layer of the glass system are optimized using the genetic algorithm. The genetic algorithm is used alongside regression analysis to determine the relative concentration of each oxide needed to obtain the best radiation shielding parameter values. The use of numerical methods is employed to ascertain simple functions that can be used instead of traditional analytical functions in modeling the behavior of glasses. The auto-Zeff software is used to generate a plot of the effective atomic number over a spectrum of photon energies, while spectroscopic techniques are used to examine the structure and optical properties to determine what advantages the glasses have over concrete or water. This approach had fast convergence due to increased numerical stability. The optimal solution is equal to barite concrete in gamma-ray shielding and limonite concrete in neutron shielding. Highlights • The genetic algorithm is successfully applied to the optimization of oxide glass. • B 2 O 3 -SiO 2 -Bi 2 O 3 -BaO glasses have HLV below 2.8 cm at 662 keV. • B 2 O 3 -SiO 2 -Bi 2 O 3 -BaO is comparable to heavy concrete in shielding parameters. • The correlation between wt. fraction and shielding parameter simplifies optimization. • Higher oxygen content in HMO glasses improves neutron shielding. [ABSTRACT FROM AUTHOR]

Abstract In the present paper, transparent and non-toxic Bi 2 O 3 -B 2 O 3 glasses doped with BaO have been prepared by the authors which may replace the standard radiation shielding concretes and lead based commercial glasses for gamma ray shielding applications. The effects of BaO on the structural and optical properties of the prepared glass system have been investigated by Raman, FTIR and UV–Visible techniques. It has been observed that barium plays the role of a modifier and it is responsible for conversion of triangular [BO 3 ] units to tetrahedral [BO 4 ] units along with formation of non-bridging oxygen and increase in ionic character. It also improves the radiation shielding abilities of the glass system. The mass attenuation coefficients for gamma-ray photons at 662 keV energy by using 137Cs radioactive source have been measured by employing narrow beam transmission geometry. This was accompanied by theoretical computation of mass attenuation coefficients in the wide photon energy range varying from 1 keV to 100 GeV. It has been found that values of mean free path and tenth value layer decrease whereas, density and effective atomic number increase with the increase of barium oxide content. As compared with barite concrete and commercial shielding glass RS-360, our prepared Bi 2 O 3 - BaO - B 2 O 3 glasses have shown better gamma ray shielding properties. This implies that the prepared glass system is a better gamma ray absorber and it has the potential for use in gamma-ray shielding applications. Graphical Abstract Unlabelled Image Highlights • Glass samples of the composition 65Bi 2 O 3 -xBaO-(35-x)B 2 O 3 where x = 0 to 10 wt% have been prepared by melt-quenching technique. • The addition of BaO in the glass system improves the gamma radiation shielding properties. • Transparent and environmental friendly nature of glasses system make them practical solution for gamma ray shielding applications. [ABSTRACT FROM AUTHOR]

Electron Paramagnetic Resonance (EPR) and Optical absorption studies were investigated in CuO doped (30-x)CdO-xAl2 O3 - 35 Bi2 O3 - 34 B2 O3 -1CuO glasses (x=0, 5, 10, 15 mole %) were prepared by melt quenching technique. The amorphous nature of all the glass samples were confirmed by XRD technique. By using the EPR and Optical absorption measurements techniques the structural changes in the above glass system was estimated and it was confirmed that Cu2+ ions were present in tetragonally distorted octahedral sites elongated along z-axis with dx²y²) orbital (²B1g) ground state in all of the glasses investigated. Bonding parameters had been evaluated by correlating EPR and optical absorption data. The molecular orbital band parameter values of (30-x)CdO- xAl2 O3 - 35 Bi2 O3 - 34 B2 O3 -1CuO glasses values indicated in plane -bonding ((²) is moderately ionic. The in plane -bonding ((²) is ionic in nature and out of plane -bonding (('2) is shifting from moderately ionic to ionic as we move from CABBC1 to CABBC3. The FTIR spectra revealed information about the nature of bonds present in the glass matrix. [ABSTRACT FROM AUTHOR]

Abstract Glasses with nominal molar composition 20B 2 O 3 – (80−x)Bi 2 O 3 – xFe 2 O 3 (where x = 0–40) were successfully prepared by melt-quenching. These glasses were characterised by multiple techniques including density, X-ray diffraction (XRD), X-Ray fluorescence (XRF), Raman, FT-IR and Mössbauer spectroscopies, dilatometry and differential thermal analysis (DTA). Partial replacement of Bi 2 O 3 by Fe 2 O 3 leads to decreasing density and molar volume and a substantial increase in thermal stability, as measured by several parameters, with maximum improvements achieved when x = 10–20. These improvements are accompanied by modest increases in dilatometric softening point. FT-IR and Raman spectra confirm the presence of BO 3 and BiO 6 structural units in all glasses, with glass structure apparently little affected by Fe 2 O 3. Mössbauer spectroscopy confirms that iron is present partly as 4-fold coordinated Fe3+ in all glasses, with some 5- and/or 6- coordinated Fe3+ sites also present. [ABSTRACT FROM AUTHOR]

Transparent Alkaline Bismuth Borate glasses (10RO-35Bi 2 O 3 -55B 2 O 3 , where R = Ba, Ca & Sr) were prepared by melt-quenching method. The optical band gap values of the glasses are obtained from absorption spectra and found to increase due to the presence of alkaline earth ion in the order of Ba < Sr < Ca whereas optical basicity values follows the reverse trend. Nonlinear optical properties and optical limiting properties of the glasses were investigated at wavelengths of 532 and 800 nm for ns and ps and fs time domains respectively by Z-scan technique. Two-photon absorption is regarded as the dominant mechanism in the case of Sr and Ca based glasses whereas glass with Ba exhibit two photon induced three photon mechanism. Optical limiting characteristics are also reported in fs and ns regimes for these glasses. [ABSTRACT FROM AUTHOR]

In the present research, the Li 2 ZnTi 3 O 8 (LZT) ceramics were synthesized throughout solid-state ceramic processing, then mixed with bismuth borate (BiBO) glass prepared based on conventional melt quenching method. Wetting behavior of BiBO glass on the LZT ceramic substrate was monitored by hot stage microscopy. Afterward, dielectric LZT ceramics containing different amounts of BiBO glass (0.25–6 wt%) were sintered at various temperatures. X-ray diffraction and electron back scatter diffraction examinations revealed the presence of two crystalline phases of Li 2 ZnTi 3 O 8 and Bi 2 Ti 2 O 7 . The maximum value of relative density (above 95%) was obtained in the case of specimens contained more than 5 wt% glass. The microwave dielectric properties of the finally sintered BiBO glass containing LZT ceramics were as follows: dielectric constant (ε r ) = 21.44–25.09, quality factor (Q × f) = 10839–54708 GHz and temperature coefficient of resonant frequency (τ f ) = (− 15.58) − (− 12.86)ppm/°C. [ABSTRACT FROM AUTHOR]

Transparent glasses have a large number of applications in the industry of electronics as well as optical devices. xMnO-(25- x) BiO-75HBO (0 ≤ x ≤ 1.5 mol.%) transparent glasses have been prepared via melt-quench technique and characterized using dc electrical measurements, and by analyzing x-ray diffraction and Fourier transform infrared (FTIR) spectra. These characteristics were examined to understand the role of modifier oxides, i.e., BiO and MnO in the BO glass network. Adding MnO into a glass network causes structural changes, which are responsible for any variations in electrical characteristics of bismuth borate glasses. Manganese bismuth borate glasses (MBBG) show Ohmic conduction at low fields; however, glasses with higher manganese content seem to conduct through bulk limited Poole-Frenkel mechanism. FTIR spectroscopy analyses depict the presence of BO and BO groups along with B-O-B and Bi-O-Bi bonding vibrations. Glasses with higher MnO content also show Mn-O bond vibrations. The reduction of BO groups and increase of BO units lead to the formation of non-bridging oxygens (NBOs) which are responsible for the variations in the electrical properties of these glasses. [ABSTRACT FROM AUTHOR]

In order to test the prediction that Bi 2 O 3 could function as a replacement for PbO in preparing glass with zero stress-optic response, a series of bismuth boroaluminosilicate glasses of the form Bi 2 O 3 x (0.86B 2 O 3 -0.10SiO 2 -0.04Al 2 O 3 ) 1 − x were prepared. These glasses were then subjected to structural characterization and optical analysis. 11 B and 27 Al magic angle spinning nuclear magnetic resonance spectroscopy, Raman spectroscopy and optical absorption spectroscopy were used to track the structural evolution of the glasses across the series, while the Sénarmont method was employed to determine the stress-optic coefficient. Experiments indicated a zero stress-optic composition containing roughly 59 mol% Bi 2 O 3 . Various model glass structures were evaluated in the context of our previous model involving bond lengths and coordination numbers, and it was found that the prediction of this model was reasonable but that the elasto-optic response of the Bi-O bonds appears to be weak compared to that in Pb-O bonds. [ABSTRACT FROM AUTHOR]

Sapphire plates were directly bonded with bismuth borate glass braze, 50Bi 2 O 3 −50B 2 O 3 (mol%), at 700 °C for 20 min in air. The microstructure of the sapphire/sapphire joint was studied and the interfacial phases were characterized in detail. The results showed that Al 4 B 2 O 9 was the main product within the joint domain, the typical microstructure of a joint was the sapphire substrate/glassy phase + Al 4 B 2 O 9 /the sapphire substrate. [ABSTRACT FROM AUTHOR]

Zinc sodium bismuth borate (ZNBB) glasses doped with different concentrations of europium were prepared by conventional melt quenching method and characterized through the measurements of density, refractive index, X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectra, optical absorption, luminescence and radiative lifetimes. FTIR spectra showed seven characteristic peaks of bismuth and borate functional groups in the range of 400–1600 cm −1 . The optical band gap and bonding parameters have been calculated from absorption spectra. Photoluminescence spectra recorded in the visible region with 394 nm excitation are used to calculate the Judd-Ofelt (JO) intensity parameters (Ω 2 and Ω 4 ). The JO intensity parameters have been used to calculate the radiative parameters such as branching ratio (β), stimulated emission cross-section ( σ se ), transition probability (A) for the fluorescent level of 5 D 0 → 7 F 2 . Decay rates through single exponential are used to calculate the lifetime (τ m ) of the meta-stable state 5 D 0 of (Eu 3+ ion) these glasses. The radiative parameters measured for all these glasses show 0.7 mol% europium doped zinc sodium bismuth borate glass 5 D 0 → 7 F 2 transition has the potential for red laser applications. The quality of the colour emitted by the present glasses are estimated quantitatively by CIE chromaticity coordinates, which confirms the suitability of these glasses as a red emitting material for field emission technologies and LEDs. [ABSTRACT FROM AUTHOR]

The poor thermal stability of current commercial white light emitting diodes (WLED) fabricated using a blue chip, a yellow YAG:Ce 3+ phosphor (YAG) and resins, restricts their application in fields where long service time and high power lighting systems are required. Incorporating YAG into glass offers a possible way to resolve the problem by removing the organic resins in LED encapsulation. In the present study, YAG glass-ceramics with bismuth borate glass matrices were prepared using a rapid melt quenching technique. The YAG erosion mechanism was investigated for the first time in various glass matrix compositions at different co-sintering temperatures. The results demonstrate that neither B 2 O 3 nor Bi 2 O 3 individually erodes YAG particles, but the mixtures of B 2 O 3 and Bi 2 O 3 binary glass systems react with YAG and dissolve it almost completely or generate YAl 3 (BO 3 ) 4 (abbreviated as YAB), and they even erode as-produced YAB again under certain conditions. The production of YAB particles increases with the increase of the n Bi /n B ratio at a lower temperature (680 °C), while it first increases and then decreases at a higher temperature (800 °C). The maximum production of YAB can be obtained at the co-sintering temperature of 680 °C with an n Bi /n B ratio of 55:45 or at 760 °C with an n Bi /n B ratio of 35:65. The intermediate Bi 4 B 2 O 9 phase is found during the transformation of YAG into YAB. A simple but efficient approach is proposed to prevent YAG erosion and increase the luminous properties of YAG glass ceramics to a great extent by simply adding Ca 2+ into bismuth borate glass matrices. The degree of YAG erosion decreases with increasing Ca 2+ concentration until an impurity phase appears when the Ca 2+ concentration exceeds 20 mol%. The combination of good white light emission and suitable quantum efficiency as well as higher thermal stability makes the as-prepared YAG glass-ceramics equipped with a blue chip a possible alternative to commercial WLED. [ABSTRACT FROM AUTHOR]

The present work reports the frequency, temperature and composition dependence of ac & dc conductivity, dielectric constant and impedance spectroscopic parameters for glass system having composition x (2CoO·V 2 O 5 )·(30 − x )Li 2 O·20Bi 2 O 3 ·50B 2 O 3 ( x = 0.0, 2.0, 5.0, 7.0 and 10.0 mol%), 7CoO·23Li 2 O·20Bi 2 O 3 ·50B 2 O 3 and 7V 2 O 5 ·23Li 2 O·20Bi 2 O 3 ·50B 2 O 3 synthesized through melt-quench route. The investigations are carried out overwide ranges of frequency (1 kHz–5 MHz) and temperature (100 °C–400 °C). The effects of mixed-transition metal ions (i.e. Co and/or V-ions) on ac conductivity and dielectric properties have been investigated using impedance spectroscopy. Jonscher power law (JPL) is observed to be followed by all synthesized glass compositions. A synergic change in values of all electric and dielectric parameters at 7.0 mol% confirms the structural modification due to mixed transition metal ion effect in present glass system. Electric modulus of prepared glass samples exhibits an asymmetric peak for the imaginary part (M″) reflecting a non-Debye type relaxation. The complex impedance curves (Z′ (ω) vs. Z″ (ω)) for all glass samples were plotted and found to exhibit good single well-shaped semi circles over the studied temperature range which depicts a single conduction mechanism. Dc conductivity at constant applied voltage (10 Volts) is also measured. Conductivity plots and electric modulus spectra were scaled according to the Summerfield Scaling Model. Both scaling behavior reflected the time temperature superposition principal and temperature independent conduction mechanism in the present glass system. [ABSTRACT FROM AUTHOR]

Calcium bismuth borate glasses doped with Eu 3 + were prepared using a rapid melt quenching technique. The general physical properties of the glasses, including density, molar volume, and refractive index, were studied. Furthermore, the structural and optical properties as well as the thermal stability of the glasses were investigated. Eu 3 + melts homogeneously in the glass samples and acts as an effective activator. The largest absorption and excitation peak appears at 465 nm in the spectra, and intense emission occurs at 613 nm. The excited and emitted spectral intensities were observed to first increase and then decrease with increasing Eu 3 + concentration. The glass sample containing 3% (mole fraction) Eu 2 O 3 exhibited the optimum doped concentration, and it was determined that concentration quenching does not result from the non-relaxation of the 5 D 0 energy level. The glass structures were observed to become more compact with an increasing Eu 3 + concentration, and the symmetries decreased. Overall, the glasses maintained the amorphous states. [BO 3 ], [BiO 3 ], [BO 4 ] and [BiO 6 ] units appear in the glass samples, and the variation in the [BiO 6 ] units shows an inflection point. Briefly, the glass sample containing 3% Eu 2 O 3 exhibits many beneficial properties, such as high thermal stability, an appropriate refractive index and the ability to match the blue-light emission of LED chips. The glass therefore expected to be as candidate for white light emitting diode glass ceramic applications. [ABSTRACT FROM AUTHOR]

Alumina ceramics with 95 wt.% purity were sealed together using a bismuth based glass, 40Bi 2 O 3 –40B 2 O 3 –20ZnO (mol.%). The wettability of the glass on the Al 2 O 3 substrate was investigated. The results showed a contact angle of ≤36.5° was achieved when the temperature was ≥630 °C. Subsequently, sealing cycles were performed at temperatures of 520–700 °C for 30 min. The dependence of microstructure evolution of the joints on temperature was investigated. Bi 24 B 2 O 39 was detected to be the product in the joints sealed at 530–580 °C, while ZnAl 2 O 4 was identified to be the main product when sealing at temperature of ≥650 °C due to the reaction between the Al 2 O 3 substrate and ZnO from the glass. The influence of dwelling time at 700 °C on microstructure evolution of the joints was also studied. The results showed that the size of ZnAl 2 O 4 increased with increasing holding time. [ABSTRACT FROM AUTHOR]

In this work heavy bismuth-borate glasses were studied as host matrices of Dy 2 O 3 rare earth, for potential application as scintillator materials in high energy physics experiments and in general radiation detection systems. Glass matrices were prepared from 20BaO-xBi 2 O 3 -(80-x)B 2 O 3 (x = 20, 30, 40 mol%) ternary systems and synthesized by the melt-quenching method at different temperatures in order to obtain high density and high transparency in the UV/Vis range. Particularly, the glass manifesting the higher transparency and with sufficiently high density was doped with Dy 2 O 3 (2.5 and 5 mol%) in order to induce the luminescence characteristics. The effects of Bi 2 O 3 and Dy 2 O 3 on density, thermal behaviour, transmission as well as luminescence properties under UV excitation, were investigated. The experimental results show that the synthesized glasses can be considered promising candidate materials as dense scintillators, due to the Dy 3 + centres emission. [ABSTRACT FROM AUTHOR]

The present research communication deals with some significant outcomes related to the compositional dependence of optical absorption in magnesium oxyhalide bismuth borate glasses. These vitreous materials have been synthesized over very wide composition range of x Mg X 2 ·(30– x )MgO·20Bi 2 O 3 ·50B 2 O 3 ( X = Cl, F, Br and x = 0, 2, 5, 7, 10 mol%) via convenient melt-quench route. The analysis of fundamental absorption edge (from UV–Vis spectroscopy data) has been carried out in order to obtain optical band gap ( E opt ) and band tailing parameter ( B ) corresponding to indirect allowed and forbidden Mott’s transitions. The non-linear compositional variations of E opt have predicted a dual role (network former and modifier) of halogen ions in the magnesium bismuth borate matrix. Moreover, evaluation of Urbach’s energy has been done and order of its values indicates the presence of phonon-assisted indirect transitions in each synthesized composition. [ABSTRACT FROM AUTHOR]

Amorphous bismuth borate zinc glass with a composition of 40Bi 2 O 3 –40B 2 O 3 –20ZnO (in mol.%) was used as a braze to join 95 wt.% purity alumina ceramics (95Al 2 O 3 ) in air. The interfacial phases in the brazed joints were characterized using scanning electron microscopy, transmission electron microscopy. Zinc aluminate (ZnAl 2 O 4 ) was identified as the main reaction product in the joints due to the chemical reaction between the Al 2 O 3 substrate and ZnO from the glass. Typical microstructure of the Al 2 O 3 /Al 2 O 3 brazed joints was Al 2 O 3 substrate/glassy matrix phase + ZnAl 2 O 4 particles/Al 2 O 3 substrate. The dependence of the microstructure and mechanical properties on brazing temperature was investigated. The size of ZnAl 2 O 4 increased with an increase in brazing temperature. It was found the room lap shear strength of Al 2 O 3 /Al 2 O 3 joints firstly increased and then declined with increasing brazing temperature. The maximum lap shear strength of 95 MPa was obtained for the samples brazed at 675 °C for 30 min, which was mainly attributed to the formation of ZnAl 2 O 4 . [ABSTRACT FROM AUTHOR]

Bismuth borate zinc glass, 50Bi 2 O 3 –30B 2 O 3 –20ZnO (mol.%), was used as a braze intended to join sapphire. Thermal properties of the glass were all experimentally determined. The wettability of the glass on sapphire was investigated. The contact angle not greater than 11.3° was obtained in air at temperatures of ≥700 °C. Subsequently, sapphire was successfully joined to themselves at 700 °C for 20 min. The microstructure of the joint was studied and the interfacial phases were characterized. The results showed that the ZnAl 2 O 4 phase was formed as a result of the reaction between the sapphire substrate and ZnO from the glass. The mechanical integrity of the joints was investigated. The joints with an average room shear strength of 70 MPa were achieved. The fracture analysis indicated that the fracture occurred within the glass interlayer rather than at the sapphire/glass interface, hence indicating a good bonding of the glass with sapphire. [ABSTRACT FROM AUTHOR]

Developing state-of-the-art materials for protecting human from unwanted ionizing radiations is urgent and significant for the rapid development of nuclear facilities. Here, bismuth borate nanoparticles have been fabricated via a facile sol-gel process. Characterization with X-ray diffraction, scanning electron microscopy, and transmission electron microscopy reveals that the product is composed of high-purity orthorhombic Bi 6 B 10 O 24 phase and exhibits a typical single crystal with the size ranging from 100 to 300 nm. The product has an excellent ability to jointly attenuate both neutron and γ-ray. This significant work provides a material with not only good radiation shielding but also other fascinating features, such as environment-friendly. [ABSTRACT FROM AUTHOR]

Dy 3+ doped alkaline earth bismuth borate glasses were prepared by the conventional melt-quenching method. The prepared glasses were characterized by absorption, excitation, emission and decay curves. Judd–Ofelt parameters were obtained from the absorption spectra recorded at 400–2000 nm. All the samples were excited at different wavelengths from UV (350 nm) to blue (450--470 nm) light and respective emission spectra are recorded. The intensity ratio of yellow to blue (Y/B) indicates that Dy 3+ ions are present in low symmetry site. B 2 O 3 –Bi 2 O 3 RO (R = Ba, Sr & Ca) glasses emit efficient white light under different excitation wavelengths, which match well with the emission of commercial GaN-based blue LEDs and InGaN-based LEDs respectively. CIE coordinates were calculated from the emission spectra and found that they fall in white light region. Decay curves show single exponential nature up to 1 mol% of Dy 3+ concentrations and then turn into non-exponential for 2 mol% of Dy 3+ ions. Lifetime of these glasses decreases with increase of Dy 3+ ion concentration. [ABSTRACT FROM AUTHOR]

The total set of polarized Raman spectra have been obtained at room temperature, and an assignment of observed modes based on the lattice dynamics simulation and polarization selection rules is proposed. An LO-TO splitting of A1Raman bands have been observed. [ABSTRACT FROM PUBLISHER]

According to the own nature and its related optical characteristics of Nd:YVO 4 crystal, a set of compact all-solid-state laser system at 457 nm was designed. At the same time the parameters of the temperature control system and the resonant cavity were also optimized. Based on the realization of Nd:YVO 4 laser crystal operation at 914 nm wavelength, 457 nm laser output were obtained by intracavity frequency doubling with LBO and BIBO crystal. The M 2 factor was 1.38 and 1.57 by the LBO and BIBO intracavity frequency doubling experiments. Under the pump power of 24.3 W, the output power of 2.34 W and 1.56 W is obtained, respectively, with the same experimental condition. The optical-to-optical efficiency is 9.74% and 6.45%. [ABSTRACT FROM AUTHOR]

Bismuth borate glasses with composition 20Bi2O3.80B2O3 containing 2·0 mol% of transition metal ions having magnetic character (Cu2+, Co2+, Ni2+, and Fe3+) prepared by the melt-quench technique have been investigated for their structural, thermal and optical properties. Glass formation is confirmed by x-ray diffraction (XRD). The density (D) and molar volume (Vm) of prepared have been measured and correlated with the structural changes. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) are carried out in the temperature range of 200-1000°C. The glass transition temperature (Tg) and glass melting temperature (Tm) are found to increase on adding transition metal ions (TMIs) to the bismuth borate glass matrix indicating the decreased glass fragility. The absence of weight loss observed from the TGA thermographs shows that the synthesized compositions are non-volatile. Study of infrared (IR) spectroscopy in mid-IR range (400-4000 cm-1) reveals an increase in tetrahedrally coordinated boron atoms and hence formation of nonbridging oxygens (NBOs). The optical band gap (Eopt), band tailing parameter (B) and Urbach energy (DE) are calculated and reported from the optical absorption results. A decrease in optical band gap is observed on adding transition metal ions to pure bismuth borate glass. [ABSTRACT FROM AUTHOR]

Bismuth borate glasses with compositions x (Bi 2 O 3 ) × (100 − x) (B 2 O 3 ) (where x is in mol. % ranging from 25 to 50 in steps of 5) have been prepared by using melt quenching technique. The glass transition temperature (T g ) of the prepared samples has been measured. It was found that the glass transition temperature (T g ) decreases with increasing Bi 2 O 3 content which indicates that the degree of disorder increases. Furthermore, the density, molar volume and oxygen packing density have been studied. It has been found that the density increases as well as the molar volume. However, the oxygen packing density decreases by increasing the Bi 2 O 3 content which gives an indication that the structure becomes loosely packed. Positron Annihilation Lifetime (PAL), Fourier Transform Infra-Red (FT-IR) and X-ray Diffraction (XRD) measurements have been performed to study the amorphous and defect structure as well as the vibrating band structure. PAL results have revealed weak formation of ortho-positronium (o-Ps) at amorphous sites. The correlation between the optical properties deduced from FT-IR spectra, and the positron annihilation lifetime parameters has been investigated. The decrease of the annihilation lifetime τ 2 of trapped positrons at defects with Bi 2 O 3 , suggests a free annihilation of positrons at non-bridging oxygen (NBO) bonds, which is also evidenced by the positive correlation between I 1 and the number of NBO atoms. FT-IR spectra revealed the presence of some bonds, that are assigned to vibrations of Bi–O bonds from [BiO 3 ] pyramidal and [BiO 6 ] octahedral units and B–O bonds from [BO 3 ] and [BO 4 ] units. On the other hand, increasing Bi 2 O 3 have led to increase in the optical basicity or polarizability up to 35% concentration because the ionic radii of Bi 2 O 3 is larger than those of B 2 O 3 . Consequently, a decrease in the optical band gap energy (E g ) with Bi 2 O 3 is observed. [ABSTRACT FROM AUTHOR]

As lanthanide doped upconverting host, two dimensional (2D) nanostructure materials have remarkable advantages compare with the bulk materials, but excellent 2D upconversion nanohost is still few up to date. In this work, Yb 3+ /Ho 3+ co-doped BiOBr nanosheets have been successfully prepared via a facile hydrothermal method, which were characterized by X-ray diffraction, transmission electron microscopy, Atomic Force Microscope, Raman spectra, Fourier transform infrared absorption and UC luminescence spectra. Under excitation at 980 nm, bright green UC emission centered at 550 nm accompanied with weak red (663 nm) and near infrared (NIR) UC emissions (760 nm) were observed. Power dependence studies revealed that NIR and red UC emissions were both dominated by a two and one-photon process due to saturation effects that is related to the special crystal structure of BiOBr nanosheets, and a different UC mechanism of NIR emission from Ho 3+ was proposed accordingly. [ABSTRACT FROM AUTHOR]

Zinc bismuth borate (ZBB) glasses with chemical composition of (60 − x ) B 2 O 3 : 30Bi 2 O 3 : 10ZnO: x Eu 2 O 3 for different Eu 2 O 3 concentrations of x = 1, 3, 5, 7 and 9 mol% were prepared by the conventional melt quenching technique. The density and molar volume of the glasses have been found to increase with Eu 2 O 3 concentration. The IR studies indicated that these glasses were made up of [BiO 3 ], [BO 3 ], [BO 4 ] and [BO] basic structural units. The absorption spectra had revealed two intense bands due to 7 F 0 → 7 F 6 (2076 nm) and 7 F 1 → 7 F 6 (2198 nm) transitions in the NIR regions. The fractional populations of the ( 7 F 0 ) and ( 7 F 1 ) ground state were 65% and 35% , respectively. Five luminescence bands were observed at 579 nm ( 5 D 0 → 7 F 0 ), 589 nm ( 5 D 0 → 7 F 1 ), 613 nm ( 5 D 0 → 7 F 2 ), 651 nm ( 5 D 0 → 7 F 3 ) and 696 nm ( 5 D 0 → 7 F 4 ), when excited by a 465 nm source, the most intense red emission was found at 613 nm. A shorter decay time of 5 D 0 excited state was found with increasing of Eu 3+ concentration as more asymmetries were created around Eu 3+ . For comparison, further investigations were carried out with two other glass structures; bismuth borate glass (BB) and zinc borate glass (ZB), doped with Eu 3+ in the same range. The ZBB glasses have exhibited with the highest emission intensity especially at 613 nm; the intensity for the ZBB was around 7 times of the ZB and twice of the BB glasses. [ABSTRACT FROM AUTHOR]

The thermal behavior of barium and bismuth borate BaBiBO is studied by X-ray powder and single-crystal diffraction in a wide temperature range, as well as by the methods of differential scanning calorimetry and dielectric spectroscopy. Thermal expansion is anisotropic, which is caused by the orientation of BO boron-oxygen groups. With increasing temperature, the degree of anisotropy of thermal expansion increases up to negative. In the temperature range of 700-800 K, an anomaly of the dielectric properties is observed, accompanied by the change of the temperature dependence of the coefficients of thermal expansion and the heat capacity. [ABSTRACT FROM AUTHOR]

The coefficients of thermal expansion and the complete set of elastic stiffness coefficients of monoclinic Bi4B2O9 were determined as functions of temperature employing dilatometry and, respectively, a combination of resonant ultrasound spectroscopy and the plate resonance technique. Thermal expansion as well as elasticity of Bi4B2O9 exhibit a pronounced anisotropy, with the directions of the maximum longitudinal elastic stiffness and of the minimal longitudinal thermal expansion running almost parallel to [1̅02]. Further, between 100 K and 535 K the principal axes system of the linear thermal expansion rotates by more than 30° around the 2-fold symmetry axis. The deviations from Cauchy-relations show a similar behavior. Both, the anisotropy and the temperature induced changes of the investigated properties are mainly controlled by the stereochemically active Bi 6 s2 lone electron pairs. At room temperature their Wang-Liebau vectors possess preferred components within a plane that runs almost perpendicular to [1̅02]. A systematic analysis of the elastic behavior of bismuth oxides using the quasi-additivity rule for elastic S-factor reveals a general trend: With decreasing relative amount of Bi2O3 the Bi3+ cations tend to align their stereochemically active lone electron pairs in planes or eventually in one direction. With respect to the elastic behavior of the compound the alignment of the easliy deformable lone electron pairs is unfavorable and causes an elastic softening. [ABSTRACT FROM AUTHOR]

The coefficients of thermal expansion and the complete set of elastic stiffness coefficients of monoclinic Bi4B2O9 were determined as functions of temperature employing dilatometry and, respectively, a combination of resonant ultrasound spectroscopy and the plate resonance technique. Thermal expansion as well as elasticity of Bi4B2O9 exhibit a pronounced anisotropy, with the directions of the maximum longitudinal elastic stiffness and of the minimal longitudinal thermal expansion running almost parallel to [1̅02]. Further, between 100 K and 535 K the principal axes system of the linear thermal expansion rotates by more than 30° around the 2-fold symmetry axis. The deviations from Cauchy-relations show a similar behavior. Both, the anisotropy and the temperature induced changes of the investigated properties are mainly controlled by the stereochemically active Bi 6 s2 lone electron pairs. At room temperature their Wang-Liebau vectors possess preferred components within a plane that runs almost perpendicular to [1̅02]. A systematic analysis of the elastic behavior of bismuth oxides using the quasi-additivity rule for elastic S-factor reveals a general trend: With decreasing relative amount of Bi2O3 the Bi3+ cations tend to align their stereochemically active lone electron pairs in planes or eventually in one direction. With respect to the elastic behavior of the compound the alignment of the easliy deformable lone electron pairs is unfavorable and causes an elastic softening. [ABSTRACT FROM AUTHOR]

We prepared a series of lead and bismuth borate glasses by varying PbO/Bi 2 O 3 content and studied refractive index and optical band gap as a function of glass composition. Refractive indices were measured very accurately using a Brewster’s angle set up while the optical band gaps were determined by analyzing the optical absorption edge using the Mott–Davis model. Using the Lorentz–Lorentz method and the effective medium theory, we calculated the refractive indices and then compared them with the measured values. Bismuth borate glasses show better agreement between the calculated values of the refractive index and experimental values. We used a differential method based on Mott–Davis model to obtain the type of transition and optical band gap ( E opt ) which in turn was compared with the value of E opt obtained using the extinction coefficient. Our analysis shows that in both lead and bismuth borate glasses, the optical band gap arises due to direct forbidden transition. With increasing PbO/Bi 2 O 3 content, the absorption edge shifts toward longer wavelengths and the optical band gap decreases. This behavior can be explained in terms of changes to the Pb O/Bi O chemical bonds with glass composition. We obtained a new empirical relation between the optical band gap and the refractive index which can be used to accurately determine the electronic oxide polarizability in lead and bismuth oxide glasses. [ABSTRACT FROM AUTHOR]

Glasses from cement kiln dust and lead barium bismuth borate were prepared by the melt quenching method and studied by using FTIR and ultrasonic techniques before and after exposure to gamma irradiation at doses up to 120 kGy. The FTIR results indicated a deformation of the lead borate based glasses with the replacement of PbO by Bi 2 O 3 which was attributed to the appearance of Bi–O stretching vibrations in [BiO 6 ] structural units and generated excess of non-bridging oxygens. This deformation affected the [BO 3 ] units which are indicated from the lower decreasing rate of N 4 as a function of Bi 2 O 3 . The high covalency of Pb–O and B–O bonds compared with that of Bi–O or Si–O attracts the excess of non-bridging oxygens and resulted in a relaxation of the glass network. The relaxation decreased the ultrasonic velocities and the bulk modulus and hence the rigidity of the glass despite the increase of the density which was attributed to the replacement of Bi 2 O 3 instead of PbO. The structural and rigidity changes due to composition variations showed a decreasing manner to the effects of radiation. The density of the glass increased while the ultrasonic velocities decreased. This behavior modulated the compositional behavior of the elastic moduli on Bi 2 O 3 content. [ABSTRACT FROM AUTHOR]

Er 3+ doped Zinc Alumino Bismuth Borate (ZnAlBiB) glasses with composition 20ZnO+10Al 2 O 3 +(10− x )Bi 2 O 3 +60B 2 O 3 + x Er 2 O 3 (where x =0.1, 0.5, 1.0 and 2.0 mol%) were prepared by using a melt quenching technique to study their luminescence efficiency in different regions of electromagnetic spectrum using absorption, emission, up-conversion and time resolved photoluminescence spectral studies at room temperature. The Judd–Ofelt (JO) parameters evaluated by applying JO theory to the absorption spectra of Er 3+ doped ZnAlBiB glasses were used to calculate the radiative properties such as transition probability ( A R ), Branching ratios ( β R ), radiative lifetimes ( τ R ), stimulated emission cross-section ( σ s e ), gain band width ( σ s e × Δ λ P ) and optical gain ( σ se × τ R ) parameters for the prominent luminescent levels of Er 3+ . Visible and near infra-red (NIR) emission spectra have been recorded by exciting the glass samples at 486 nm and 980 nm respectively. Quantum efficiency ( η ) values for the prepared glasses were evaluated from the decay curves recorded for the NIR transition 4 I 13/2 → 4 I 15/2 . The up-conversion luminescence shown by these glasses were recorded and analysed to understand utility of these glasses as up-conversion lasers by exciting them with 980 nm laser diode. The visible, up-conversion and NIR luminescence studies indicate that Er 3+ ions doped ZnAlBiB glasses are aptly suitable for solid state lasers and optical amplifiers. [ABSTRACT FROM AUTHOR]

Oxy-chloride bismuth-borate glasses with composition xMgCl2·(30 − x)MgO·20Bi2O3·50B2O3 containing 2 mol% doping of V2O5 (x = 12, 15, 20, 25 and 30) are prepared by melt-quenching technique. The structural, thermal and optical behaviors are explained by analyzing the data obtained from density (D), molar volume (Vm), theoretical optical basicity (Λth), differential scanning calorimetry (DSC), FTIR and UV-vis results. A decrease in D and increase in Vm (except for sample MBV3 for which D is maximum) on increasing chloride content suggests the formation of non-bridging oxygen atoms. Maximum glass transition temperature (Tg) and crystallization temperature (Tx) have been observed for sample MBV3. The glass stability (S) and stability ratio (S/Tg) have been calculated from the values of Tg and Tx and both are having maximum values for sample MBV3. Study of the FTIR spectra in the mid-IR range reveals the presence of both triangular and tetrahedral coordinated boron. The optical studies through UV-vis spectral analysis show non-sharp edge. The optical band gap (Eg) is also maximum for sample MBV3 [ABSTRACT FROM AUTHOR]