Borate Glass System Research Articles

Gamma radiation shielding traits of B2O3–Bi2O3–CdO–BaO–PbO glasses

This paper evaluates the γ-radiation shielding traits of some new types of borate glasses of composition (70–x)B2O3–10Bi2O3–10BaO–10CdO–xPbO (where 0 ≤ x ≤ 20 mol%) prepared using melt quenching method. As-quenched samples were characterized to determine the effects of various PbO contents on their γ-radiation shielding properties. XRD patterns of the samples verified their amorphous nature. The Phy-X and XCOM was used to compute the mass attenuation coefficients of the glasses and then compared with the experimental data. The γ-radiation shielding performance of the proposed glasses were evaluated in terms of diverse attenuation parameters like mean free path, half and tenth value layer, atomic cross-section, electronic cross-section, effective atomic number and effective electron density. The γ-radiation shielding performance of the glasses were significantly improved with the increase of PbO contents. This new borate glass system is established to be advantageous for the radiation shielding applications.

Synthesis, mechanical characterization and photon radiation shielding properties of ZnO–Al2O3–Bi2O3–B2O3 glass system

Novel zinc alumina bismuth borate glass system was fabricated according to the empirical formula x(ZnO)–5(Al2O3)–30(BiO3)–65-x(B2O3) with x = 0, 5, 10, 15, 20, 25 and 30 mol% using conventional glass melt-quenching technique. The structural, elastic and shielding properties of the ZnO–Al2O3–BiO3–B2O3 glasses were examined by X-ray diffraction (XRD), density, molar volume, ultrasonic velocities, and EPICS2017 simulation. The glass structure's amorphous phase was confirmed by XRD measurement. From the density measurement, the addition of ZnO will increase the density from 4.275 to 5.018 g/cm3 and the molar volume decreased from 44.479 to 38.595 cm3/mol. In addition, the OPD is decreased from 67.45 to 62.19 mol/cm3. The elastic properties approximated from measured shear (VS) and longitudinal (VL) ultrasonic velocities indicated that the decrease of B2O3 in glass network cause the rigidity of glasses increased from 2300 to 2621 m/s and 4082–4540 m/s when the ZnO content increased. Meanwhile, the longitudinal (L), shear (G), bulk (K) and Young's (E) modulus increased from 71.23 to 103.43 GPa, 22.61–34.47 GPa, 41.08–57.47 GPa and 57.29 and 86.18 GPa. Besides, Poisson's ratio decreased from 0.267 to 0.250 and micro hardness increased from 3.51 to 5.75 GPa. The EPICS2017 simulation program is used to determine the radiation shielding of the glasses. The results show a very interesting results where the replacement of B2O3 by ZnO causes an improvement of the attenuation competence for the glasses.

Fabrication, structure, physical and optical features of the 50B2O3 + 25Bi2O3 + (25-x) Li2O + xSrO2 glasses

The purpose of this investigation is to study the physical, structural and optical characteristics of a newly fabricated SrO2 doped lithium bismuth borate glass system. The current glass system was fabricated according to the chemical formula 50B2O3 + 25Bi2O3 + (25-x) Li2O + xSrO2, utilizing the solid state- conventional method. It was noticed that The glass density increased from 4.821 to 5.952 g cm−3 whilst the molar volume was decreasing in the range from 32.93 to 30.44 cm3 mol−1 with increase the SrO2 insertion from 0 (BBLSr0 glasses) to 25 (BBLSr25) respectively. The structure of the fabricated glasses was inspected utilizing X-ray diffraction method which clarified that the insertion of SrO2 didn’t affect the amorphous nature of the tested samples. Furthermore, the UV–vis absorption spectrum was utilized to study the UV absorption characteristics for the fabricated glasses. The UV–vis absorption spectrum showed that the absorption and transition bands increase with insertion of the SrO2 contents. Based on the UV/Vis data, several important optical features were calculated like the energy gap (Eg), Urbach energy (Eu), oscillator energy (Eo) and energy of distribution (Ed). Increasing the SrO2 substitution ratio led to increase the optical properties where the refractive index was found to increase from 3.056 to 5.710.

Spectroscopic study of Er3+ doped borate glass system for green emission device, NIR laser, and optical amplifier applications

The 10BaO–20ZnO–20LiF-(50-x)B2O3-xEr2O3 (x = 0, 0.1, 0.5, 0.7, and 1.0 mol %) glass system was studied for green emission device, NIR laser, and optical amplifier applications. The impact of Er3+ doping was assessed through structural, optical, and thermal properties. The Er3+ ions behaved as network modifiers and decreased the network rigidity by the transformation of [BO4]→[BO3] and Non-Bridging Oxygens. This was consistent with the decrease in the glass transition temperature. Ten absorption peaks of Er3+ ion equivalent to transitions from 4I15/2 to various excited levels were quantified through their oscillator strengths. Through broadband impedance spectroscopy, the insulating property of the glass system was authenticated by the persistence of dc-conductivity in the order of 10−10 Scm−1 up to 523 K. With 378 nm excitation, a violet emission (2H9/2→4I15/2) and two intense green emissions (2H11/2→4I15/2, 4S3/2→4I15/2) were noticed. The NIR emission (4I13/2→4I15/2) was observed at 1531 nm with 378 and 980 nm excitations and the corresponding decay curves were recorded. The Inokuti-Hirayama model indicated the increase in the energy transfer and reduction in critical distance amid the Er3+ ions with doping leading to energy migration through cross-relaxations and lifetime quenching. The laser parameters were determined from Fuchtbauer-Ladenburg theory. The color coordinates of the samples were lying in the green region, with purity >89% and CCT >6000 K. The gain coefficient from McCumber theory was positive for a population inversion >50%, with a wide gain between 1460 and 1565 nm, extending the application of the glass system as an optical amplifier in the S + C communication window.

An experimental investigation on structural, mechanical and physical properties of Strontium–Silicon Borate glass system through Bismuth-Aluminum substitution

This study aimed to fabricate a high-density glass sample with superior physical, structural and mechanical properties that can be used in medical and industrial radiation facilities. For the chief purpose of originating a translucent radiation shielding with remarkable mechanical properties, a glass system of a heavy metal oxide alumino-borosilicate glass of composition (5-x)Al2O3–50SrO–25B2O3–20SiO2–xBi2O3 (0≤ x ≤ 5 wt%) was fabricated by traditional melt-quenching technique. XRD curves presented the disappearance of regular sharp lines, affirming the glassy nature of the glass system. Additionally, the determination of experimentally elastic moduli of the translucent glasses showed their good rigidity, along with good elastic constants. The comprehensive analysis of experimentally determined γ-radiation shielding parameters for all the glasses such as linear attenuation coefficient (μ) and mass attenuation coefficient (μm) have been evaluated, and derived μ amounts are in good compliance with deduced FLUKA codes respective μ outcomes. Next, by applying μ outputs, T1/2, and λ were estimated. All glasses possess exemplary absorption ability for the lower energy photons as authenticated by radiation protection efficiency (RPE). In all inspected glasses, comparatively higher density (4.115 g/cm3), greater μ, and RPE, and the minimum T1/2, and λ values were reported for superior Al–Bi4 glass sample.

Experimental investigation of zinc sodium borate glass systems containing barium oxide for gamma radiation shielding applications

Sodium zinc borate glasses doped with dysprosium and modified with different concentrations of barium oxide (0–50 mol %) were fabricated using the melting quenching technique. The structural properties of the prepared glass systems were characterized using XRD and FTIR methods. The absorption spectra of the prepared glasses were measured to determine their energy gap and their related optical properties. The density of the glasses and other physical parameters were also reported. Additionally, with the help of Photon Shielding and Dosimetry (PSD) software, we investigated the radiation shielding parameters of the prepared glass systems at different energy values. It was found that an increase in the density of the glasses by increasing the concentration of BaO significantly improved the gamma ray shielding ability of the samples. For practical results, a compatible irradiation set up was designed to check the shielding capability of the obtained glasses using a gamma ray source at 662 keV. The experimentally obtained results strongly agreed with the data obtained by PDS software at the same energy. These results demonstrated that the investigated glass system is a good candidate for several radiation shielding applications when comparing it with other commercial shielding glasses and concretes.

Radiation-induced luminescence of Ce-doped SrO–B2O3 glasses

Abstract The performance of phosphors generally depends on the local coordination of activators. The luminescence properties are also affected by the excitation light source and radiation-induced luminescence, like X-ray-induced scintillation, is quite different from conventional photoluminescence (PL) excited by UV light. Here, we have examined the optical and luminescence properties of Ce3+ in strontium borate glasses. The pulse height spectra by 241Am irradiation indicate that the X-ray induced luminescence intensity detected consists of prompt scintillation and storage luminescence. Persistent luminescence at room temperature was clearly observed in B2O3-rich glass after X-ray and UV irradiation. In the present borate glass system, B2O3-rich glass exhibiting a deep optical absorption edge is favorable for high luminescence intensity by UV irradiation and storage luminescence, while SrO-rich glass is suitable for high detection ability of α-rays.

Insight on the weak hopping conduction produced by titanium ions in the lead borate glassy system

DC conductivity investigation was conducted on the lead borate glass system of the composition (75–x) PbO–25B2O3–xTiO2, x = 15, 20, 25, and 30 mol %, to access the potential conduction mechanism controlling the conductivity data of the present glass system. The melt quenching method was utilized to prepare this glassy system. The amorphous nature of the present glass system was asserted by SEM. The theoretical density of the present glass system was larger than the corresponding measured one, affirming the completely amorphous essence of these glasses. The conductivity of these glasses slightly increased with TiO2 additions. Strikingly, when the Pb-ions become attached to Ti-ions in the glass matrix they minimize their hopping motions, leading to the occurrence of the weak hopping process in these glasses. Accordingly, PbO played a vital role in revealing the weak hopping without needing low-temperature measurements close to absolute temperature. The conduction mechanism in these glasses was determined by different models arising from the typical hopping of charge carriers. The polarons hopping occurred in the non-adiabatic process. The values of different parameters, such as small polaron coupling and hopping carrier mobility, asserted the occurrence of the weak hopping process in these glasses. The Greaves VRH model was proper to elucidate the conductivity data of these glasses.

In-depth survey of nuclear radiation attenuation efficacies for high density bismuth lead borate glass system

MCNPX, Geant4 and FLUKA codes are employed to compute mass attenuation coefficients (μ/ρ) for 20Bi2O3-(80-x)B2O3-xPbO (x = 0, 20, 30, 40 and 60 mol%) glasses at 20, 30, 40 and 60 KeV, 133Ba (81, 161, 223, 276, 303, 356 and 384 keV), 57Co (122 and 136 KeV), 22Na (511 and 1275 keV),137Cs (662 keV),54Mn (835 keV), 60Co (1173 and 1333 keV) and 42K (1524 keV) photon peaks where 20, 30, 40 and 60 KeV energies are utilized for Mammography, Dental, General and Computed tomography (CT) scanning accordingly, in this study. All simulated μ/ρ outcomes accuracy was verified by WinXCOM and Phy-X/PSD programs’ μ/ρ findings and we noticed a satisfactory agreement among them. From μ/ρ and linear attenuation coefficient (μ) values effective atomic number (Zeff), effective electron density (Neff), half-value layer (HVL), tenth-value layer (TVL) and mean free path (MFP) have been determined. 20Bi2O3-20B2O3-60PbO (mol%) glass HVL and MFP have been compared with some commercial glasses, alloys, polymers, concretes and lead and ceramics corresponding values. Later equivalent atomic numbers (Zeq) and applying geometric progression (G–P) fitting method at 1 – 40 mfp penetration depths (PDs) at 0.015–15 MeV energy range exposure buildup factors (EBFs) and energy absorption buildup factors (EABFs) were estimated. At all selected twenty energies derived radiation protection efficiency (RPE) results confirmed studied samples’ excellent efficacy for low energy photons absorption. Moreover, applying SRIM codes mass stopping powers (MSPs) and projected ranges (PRs) for protons and α-particles and utilizing ESTAR database electron MSPs and continuous slowing down approximation (CSDA) range for electrons were determined at kinetic energy (KE) range of 0.015–15 MeV. Further fast neutron removal cross-sections (ΣR), for 0.0253 eV energy neutrons coherent and incoherent scattering cross-sections (σcs and σics), absorption cross-section (σA) and total cross-section (σT) quantities were evaluated. Derived ΣR was changed at 0.1166–0.123 cm−1 range depending on PbO addition in chosen samples. 20Bi2O3-80B2O3 (mol%) glass has larger σT (23.094 cm−1) in all studied samples for thermal neutron absorption while 20Bi2O3-20B2O3-60PbO (mol%) sample shows superior attenuation factors for photons and fast neutrons signifying included PbO positive effect.

Density, Molar Volume and IR Studies of Lithium Doped Bismuth Lead Borate Glasses

Structural analysis of 15Bi2O3-(50-x)PbO-35B2O3-xLi2CO3, x = 0,5,10,15 and 20) of lithium doped bismuth lead borate glass system (BPBL) using density, molar volume, and IR absorption spectra has been carried out for These glasses were prepared by the most reliable conventional melt quenching technique. Densities and molar volumes have been measured as a function of Li2CO3 content. Almost linear variation in the density and the molar volume has been observed in the present glasses and is attributed to the role of Li+ in these glasses. IR spectra of these glasses exhibit characteristic vibrations due to the borate network. The band at 400 cm−1-600 cm−1 due to absorption refers to metallic and cationic vibrations of metallic cations of Bi3+ and Li+.

Optical spectroscopy of chromium doped bismuth-lithium borate glasses

The optical absorption, photoluminescence, and electron spin resonance spectroscopies were used to investigate the effect of Bismuth oxide on a chromium doped borate glass system of composition 14.5% Li2O – 0.5% Cr2O3 – (85-x)% B2O3 – (x)% Bi2O3, x = 0.0, 1.0, 3.0, 5.0 and 8.0, synthesized by conventional melt quenching technique. Two sets of Cr characteristic absorption bands were identified in the ultraviolet and visible regions. The intensity and/or peak position for these transitions could be readily tuned through Bi2O3 additives. The ligand field analysis applied to the absorption spectra revealed high field sites for Cr ions as inferred from the resulting Dq/B values. The presence of Cr6+ and Cr3+ ions is further supported by the development of well-defined photoluminescence peaks. The electron spin resonance spectra complement these optical findings and clearly identify resonance signals ascribed to Cr3+ and Cr5+, the latter in particular evolves monotonically with Bi2O3 content.

Influence of heavy metal oxides to the mechanical and radiation shielding properties of borate and silica glass system

Six borate and silica glasses with varying compositions were investigated for their mechanical and radiation shielding viability. Makishima-Mackenzie elastic model was utilized to study the elastic properties of the investigated glasses. The obtained results illustrated that PbO and Bi2O3 oxides reduced the glass samples' mechanical properties. For instance, the bulks' model decreased between 68.15 and 44.10 GPa, the shear model also followed the same trend and decreased from 31.95 to 23.33 GPa, reducing the PbO and Bi2O3 ratios in the studied glass samples. Monte Carlo N-Particle Transport Code (MCNP-5) was utilized to evaluate the investigated glasses' shielding capacity. The obtained results depict that the highest linear attenuation coefficient (LAC) occurred at 0.356 MeV; it takes values 0.618, 1.024, 1.161, 1.271, 1.963, and 2.071 cm−1 for G1, G2, G3, G4, G5, and G6. Based on the simulated values of LAC, other shielding properties such as transmission rate (TR), radiation protection efficiency (RPE), half-value layer (HVL) were evaluated. The calculated results illustrated that the shielding properties enhanced with Bi2O3 and PbO insertion ratios.

Research on the effects of bismuth borate glass system on nuclear radiation shielding parameters

There has been an increasing number of research and development activities focusing on the use of different glass systems for their nuclear radiation shielding features. In this study a simulation study has been carried out at a wide photon energy region in order to investigate the radiation protection feature of bismuth borate glasses. This study has been conducted to evaluate the proficiency level of six different glass systems (70-x)B2O3 + xBi2O3 + 15ZnO + 15Na2O (where x = 0, 5, 10, 15, 20 and 25 mol%) exposed to photon, charged particle (H1) and (He+2) and neutron. For this investigation, transmission factors (TF), mass attenuation coefficient (MAC), half value layer (HVL), tenth value layer (TVL), mean free path (MFP), effective atomic number (Zeff), effective electron density (Neff) have been computed. The results confirm that the parameters of the examined glasses MAC, HVL, TVL, MFP, Zeff, and Neff are associated with photon energy and chemical composition. In addition, neutron effective cross-sections (∑R) have been computed for bismuth borates and it was seen a good harmony. The computations for present samples have been examined over a broad energy range from 0.01 to 20 MeV and theoretical results have been obtained by using MCNPX software for transmission factors. In addition, simulation results have been calculated with the WinXCom program. Furthermore, MSP and PR calculations of the bismuth borate glass have been performed to figure out the radiation shielding features. For that reason, the SRIM code has been used to simulate H1 and He+2 particles. Considering the results obtained from this research, which examines the radiation protection of bismuth borate glasses, indicates that the best shielding achievement (while the HVL, TVL, MFP, TF have the lowest and the highest (∑R) values) is reached at 25% Bi2O3. As can be seen in the results, the addition of bismuth affirms that the use of such glass systems improves the radiation protection feature. In particular, 25%Bi2O3 glass system has been proved to show superior shielding properties for gamma radiation in combination with charged particles. Since the glass sample with the highest bismuth additive is 25%Bi2O3, the most radiation protection effect is also seen in this example. The obtained material has a satisfactory radiation shielding property as bismuth is added to the mixture.

Investigation of optical and physical properties of zinc sodium bismuth borate glass system

A glass system with composition xZnO-(15-x)Na2O-15Bi2O3-70B2O3 (where x=0, 6, 8, 10, 12 mol %) have been prepared by conventional melt quenching technique in order to investigate the some physical and optical properties with impact of ZnO in the sodium bismuth borate glasses. The optical analysis of glass system is carried out by UV-Vis spectroscopic measurement technique. The optical study reveal that cut off wavelength and Urbach energy decreases while optical band gap increases with the addition of ZnO content. Further, the compositional dependence of different physical and optical parameters such as ion concentration, polaron radii, inter nuclear distance, molar refraction, molar polarizability, reflection loss, metallization criterion, refractive index and dielectric constant have also been evaluated.

Effect of bismuth and lithium substitution on radiation shielding properties of zinc borate glass system using Phy-X/PSD simulation

The radiation shielding properties of zinc borate glasses with lithium oxide replacing bismuth oxide were investigated using Phy-X/PSD. The glasses have a composition of (25-x)Bi2O3-60B2O3-15ZnO-xLi2O, where x = 5, 10, 15, 20 and 25 mol%, and are coded as S1, S2, S3, S4, and S5 in increasing Li2O content. Phy-X/PSD was used to determine the mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), half value layer (HVL), effective atomic number (Zeff), tenth value layer (TVL), and mean free path (MFP) of the investigated glasses. S1 was found to have the greatest MAC and LAC values, 0.415 cm2/g and 1.868 cm−1 at 0.2447 MeV respectively, while S5 had the least, 0.115 cm2/g and 0.301 cm−1 respectively at the same energy. The maximum HVL values was found at 1.46 MeV and are equal to 2.926 cm, 3.427 cm, 3.766 cm, 4.159 cm, and 5.222 cm for S1, S2, S3, S4, and S5 glasses, respectively. The minimum HVL values occurred at the lowest tested energy, 0.2447 MeV, and increased with increasing energy, meaning that the glasses are more effective at lower energies. The Zeff values inversely correlated with the Li2O content in the glasses, following the order of S1 > S2 > S3 > S4 > S5 at all energies. At 0.41 MeV, the Zeff values are equal to 25.15, 21.52, 17.42, 12.75, and 7.35 for S1, S2, S3, S4, and S5 respectively. At all energies, TVL decreased with increasing density; for instance, decreasing from 17.347 cm to 9.718 cm when density increased from 2.613 g/cm3 to 4.503 g/cm3 at 1.458 MeV. The MFP of the zinc borate glasses were compared against other shielding glasses and it was found that the S1 glass outperformed five of the other glasses at 0.2447 MeV and six of the others at 1.458 MeV. The results proved that the S1 glass, the glass with the greatest Bi2O3 content and density, has the greatest potential for radiation shielding applications.

Impact of Dy2O3 Substitution on the Physical, Structural and Optical Properties of Lithium–Aluminium–Borate Glass System

In this study, a series of Li2O-Al2O3-B2O3 glasses doped with various concentrations of Dy2O3 (where x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 mol%) were prepared by using a conventional melt-quenching technique. The structural, physical and optical properties of the glasses were examined by utilising a variety of techniques instance, X-ray diffraction (XRD), UV–Vis-NIR spectrometer, Fourier transform infrared (FTIR) and photoluminescence (PL). The XRD spectra demonstrate the amorphous phase of all glasses. Furthermore, the UV-vis-NIR spectrometers have registered optical absorption spectra a numbers of peaks which exist at 1703, 1271, 1095, 902, 841, 802, 669, 458, 393 and 352 nm congruous to the transitions from the ground of state (6H15/2) to different excited states, 6H11/2, 6F11/2 + 6H9/2, 6F9/2 + 6H7/2, 6F7/2, 6F5/2, 6F3/2, 4F9/2, 4I15/2, 4F7/2 and 6P7/2, respectively. The spectra of emission exhibit two strong emanation bands at 481 nm and 575 nm in the visible region, which correspond to the transitions 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2. All prepared glass samples doped with Dy2O3 show an increase in the emission intensity with an increase in the concentration of Dy3+. Based on the obtained results, the aforementioned glass samples may have possible applications, such as optical sensor and laser applications.

Effect of Mixed Transition Metal Ions in B2O3-V2O5-MoO3 Glass System

The effect of having two different transition metal oxides in a glass matrix is an interesting phenomenon to study, as this kind of composition leads to various anomalous effects in terms of electrical and other physical properties. The present series of glasses were explored for density and DC electrical conduction in borate glass systems containing molybdenum and vanadium oxides. The glasses were synthesized using the melt-quench method and their amorphous characteristics were established by XRD techniques. The glasses were explored for density and DC electronic conduction in a temperature range between 318 K and 473 K. The estimated density, molar volume and oxygen packing density (OPD) varied non-linearly with increasing MoO3 content. The DC conduction and activation energy attained maximum and minimum around 0.15 mole fraction of MoO3. This was attributed to the fact that with the addition of MoO3 up to x = 0.15 molar fraction, the V2+ transition metal ions and Mo5+ transition metal ions may create bond defects and non-bridging oxygen (NBO) by altering the bonds of boron-oxygen-boron, boron-oxygen-molybdenum, boron-oxygen-vanadium. As a result, at x = 0.15 mole fraction of MoO3, the glass linkage among the bonds becomes close or tightly packed. Consequently, the net movement of ions begins effortlessly over the pathways of the tightly packed glass system. The high-temperature conduction data were analysed following Mott’s small polaron hopping theory, and the low-temperature conduction data were analysed in terms of Mott’s and Greave’s variable-range hopping conduction models. Several polaron-related parameters were estimated and are discussed.

Observation of structural, spectral characterizations and correlation of physical parameters on VO<sup>2+</sup> ions doped Cadmium Lithium Sodium Borate glasses

A series of quinary 0.1 mol% VO2+ doped Cadmium Lithium Sodium Borate (CLNB) glass system with varying alkali (Li2O/Na2O) content were prepared by the classical melt quenching technique. The current research was carried out to observe the physical, structural and spectral parameters alter with the variation of alkali content in nonlinear manner. Physical properties such as the oxide ion polarizability ), optical basicity of prepared glass (th), Yamashita and Kuroswa’s interaction parameter ) and the third order nonlinear optical polarizability (c(3)) are calculated by compared with altering the alkali mol% and also correlate them with each other. Physical parameters are varying in non-regular pattern and were substantiated to presence of the mixed alkali effect in glass system. No sharp peaks were exhibited in XRD pattern and suggest that the prepared VO2+ doped CLNB glass systems possess the amorphous nature. FTIR spectra of glasses are revealed about the functional groups existed and bonding linkages between them. Optical absorption and EPR spectra of the vanadyl ion doped CLNB glass systems are confirmed the site symmetry of the dopant ion as tetragonally compressed octahedral site symmetry. The evaluated molecular bonding coefficients values are confirming the bonding nature of dopant ion.

Mixed-alkali effect on hardness and indentation-loading behavior of a borate glass system

In this work, we investigate the mixed alkali effect on both hardness and indendation-loading behavior of the 75B2O3•xLi2O•(25-x)Na2O (mol%) glass series. It is found that the mixed alkali effect manifests itself as a minimum in the extent of the indentation size effect (ISE). This minimum could be connected to that of the plastic deformation induced by pressure. We also study the structural responses to indentation using the Raman spectroscopy. The results show that indentation leads to both incorporation of three-coordinated boron (BIII) into medium-range order units and transformation of BIII into four-coordinated boron (BIV). This implies that the mixed-alkali effect on both hardness and indendation-loading behavior could be associated with the contributions of both short-range and medium-range order units to the structural changes.

Optical Spectroscopy and Excited-State Dynamics of Eu3+ -Doped Bismuth Borate Glasses Containing CuO.

Bismuth borate glasses containing phosphors and luminescent rare-earths are of interest for applications in light-emitting devices. Herein, the influence of CuO impurities on red-emitting Eu3+ -doped bismuth borate glasses of the 25Bi2 O3 -15BaO-10Li2 O-50B2 O3 type was investigated by various spectroscopic methods. The glasses were prepared by the melt-quench technique and characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, UV/Vis optical absorption (OA), and photoluminescence (PL) spectroscopy including decay kinetics assessment. The XRD data confirmed the amorphous nature of the glasses whereas FT-IR spectra indicated the basic structural features of trigonal BO3 units and BO4 tetrahedra. The OA analysis showed that addition of CuO up to 0.5 mol% results in significant growth of the visible Cu2+ absorption band around 715 nm, with slight decrease in the optical band gap energies assessed through Tauc plots. A drastic PL quenching of Eu3+ ions emission was evidenced concurring with the detrimental effect of Cu2+ . The assessment of the Eu3+ emission decay curves revealed significant lifetime decrease of the 5 D0 emitting state with increasing CuO concentration. An analysis of quenching constants was finally performed comparing results from integrated PL data with the emission decay rates. It is argued that the bismuth borate glass system supports an effective Eu3+ →Cu2+ energy transfer (more so than phosphates) in connection with a strong spectral overlap between Eu3+ emission and Cu2+ absorption.