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Glasses with WO 3 in place of CaO with the chemical formula 45B 2 O 3 +15TeO 2 +(18-X)CaO+22Na 2 O + XWO 3 : X = 0 (W-0), 1.5 (W-1.5), 3 (W-3), 4.5 (W-4.5), and 6 (W-6) mol% were prepared using the melt quenching method. A comprehensive study of the structural, physical, optical, and γ-ray protection properties of the prepared glasses was investigated. Density (ρ), molar volume (V m), UV–Vis measurements, the MCNP5 simulation code, and PhX software were employed to achieve the aims of this study. The density (ρ) of the W-X samples increased slightly from 2.45 g/cm3 to 2.62 g/cm3 as WO 3 content increased from 0 to 6 mol%. The molar volume (V m) evinced the same trend as ρ. In the UV range, significant absorption was observed, rising as the molar concentration of WO 3 increased. The direct optical gap (E opt.(dir.)) declined from 3.59 eV to 3.24 eV, while the indirect gap (E opt.(indir.)) declined from 3.27 eV to 2.36 eV. The Urbach energies (ΔE) ranged from 0.35 to 0.71 eV. The refractive index (n) increased from 2.33 to 2.59 as WO 3 content increased. The molar polarizability (α m) and molar refractivity (R m) increased. The linear-attenuation absorption (μ) order is: W-0 < W-1.5 < W-3 < W-4.5 < W-6. The W-6 glass sample possessed the lowest half- (HVL), and tenth- (TVL) value layer, as well as the lowest mean free path (MFP). Therefore, the W-6 glass sample offers the best gamma radiation shielding capability among the prepared W-X glasses. Within the investigated energy range, the effective atomic number (Z ef) varied from 30.773 to 13.234, 35.398–13.969, 39.089–14.670, 42.103–15.338, and 44.611–15.977 for the W-0, W-1.5, W-3, W-4.5, and W-6 glasses, respectively. At 0.080 MeV, the mass-attenuation absorption (μ m) of the investigated W-X glasses was higher than for TBLMC-X (TeO 2 –B 2 O 3 –Li 2 O–MoO 3 –CuO) and TS-X (9SiO 2 –Al 2 O 3 –Na 2 O–B 2 O 3 –TeO 2) glasses. [ABSTRACT FROM AUTHOR]

This work investigates the significant effects of SrO on the structural, physical, and UV–visible (UV–Vis) characteristics and the γ-ray and neutron shielding ability of samarium sodium borotellurite glasses with the composition (46.5-X)B2O3 + 0.5Sm2O3 + 15TeO2 + 18Bi2O3 + 20Na2O + XSrO, where X = 0 (SrO0)–12 (SrO12)% with steps of 3 mol.%, designated as SrOX. The glass samples were prepared via the well-known melt quenching technique. The amorphous nature of the fabricated glasses was confirmed by XRD. The density (ρ) of the SrOX samples increased gradually from 3.73 ± 0.01 g/cm3 to 4.04 ± 0.01 g/cm3. The direct optical gap increased from 2.94 ± 0.01 eV to 2.98 ± 0.01 eV, and the indirect gap increased from 2.74 ± 0.01 eV to 2.95 ± 0.01 eV. Several absorption peaks were found for 4f5–4f5 electronic transitions from ground manifold 6H5/2 to excited samarium ion manifold states. The free volume (Vf), packing density (Pd), ion concentration (N), polaron radius (rp), internuclear distance (ri), field strength (F), molar volume of the boron atoms (Vb), and average boron–boron distance (dBB) changed significantly as the SrO concentration varied in the glass network. The linear attenuation coefficient (µ) followed the order: SrO0 < SrO3 < SrO6 < SrO9 < SrO12. The synthesized SrO12 glass sample had the lowest half-value layer (HVL). The fast neutron removal cross-section (FCS) values of the SrOX glass samples were 0.085 cm−1, 0.085 cm−1, 0.085 cm−1, 0.086 cm−1, and 0.086 cm−1 for samples SrO0, SrO3, SrO6, SrO9, and SrO12, respectively. The obtained results showed that the proposed compositions can be used in optical applications as well as γ-ray and neutron shielding materials. [ABSTRACT FROM AUTHOR]

Effect of Dy2O3 on the properties of borotellurite glasses, (B2O3)0.2–(TeO2)0.22 – x–(ZnO)0.28–(Li2O)0.20–(WO3)0.10–(Dy2O3)x; x = 0.01 to 0.06 has been investigated. Density increased and molar volume decreased with increase of Dy2O3 and they were explained in terms of composition. Glass transition temperature increased and thermal stability decreased with increase of Dy2O3 content. Conductivity increased and its activation energy decreased up to 0.04 mole fraction of Dy2O3 and behaved in opposite way for higher amounts of Dy2O3. These results are ascribed to network changes occurring around 0.04 mole fractions of Dy2O3. For the first time the effect of Dy2O3 on conductivity has been reflected in this fashion. Polaron hopping distance, polaron radius and Debye's temperature were determined and discussed appropriately. [ABSTRACT FROM AUTHOR]

5CaF2–5BaF2 – 60B2O3–10TeO2 – (20-x)Na2O – xDy2O3: (0.5 ≤ x ≤ 2.5 mol percent) glasses were studied for their physical, mechanical, and gamma radiation resistance. The density of Dy0.5 and Dy2.5 glass samples containing 0.5 and 2.5 mol of Dy2O3 was changed from 2.98 to 3.09 g/cm3, respectively. The estimated values of longitudinal (LB-C) were altered from 171.085 to 165.390 GPa, bulk (KB–C) from 105.100 to 102.680 GPa, Young's (EB-C) from 128.602 to 122.674 GPa, and shear (SB–C) from 49.612 to 47.150 GPa for mechanical characteristics (GPa). The Poisson's ratio (σB-C) was varied between 0.296 and 0.300. The MCNPX code and Py-MLBUF online calculation platform were used to calculate mass attenuation coefficients for all Dyx-glasses. In terms of quantitative values, the acquired results are in good agreement. For all photon energies, the Dy2.5 glass sample exhibits the highest linear (μ) and mass (μm) attenuation coefficients. All analyzed Dyx-glasses exhibit a similar trend in half-value layer (T1/2) and mean free path (MFP), (T1/2, λ)Dy0.5 > (T1/2, λ)Dy1.0 > (T1/2, λ)Dy1.5 > (T1/2, λ)Dy2.0 > (T1/2, λ)Dy2.5. Over the whole gamma-ray energy range, the Dy2.5 sample has the highest effective atomic number (Zeff) values. Across the whole photon energy and penetration depth range, the Dy2.5 has the lowest EBF and EABF values. Because of the maximum contribution of Dysprosium (III)-oxide, the Dy2.5 sample can be deemed superior in terms of gamma-ray shielding qualities.

This paper presents a comparison study of absorption spectra of borotellurite glasses with compostion: 20TeO2 – 15Bi2O3 – 3TiO2 – (4-x) Na2CO3 – 1Tm2O3 - xHo2O3 where x = 0; 0.5; 1; 1.5; 2; 2.5 (mol%). All glasses are fabricated using melt quenching method. Absorption spectra were recorded at room temperature in the spectral range of 200 – 1100 nm. Within this range, glass with x = 0 mol % of Ho2O3 shows 2 absorption peaks which corresponds to electronics transition from 3H6 to state to 3F3 and 3H4. For x = 0.5; 1; 1.5; 2; 2.5 (mol%), nine absorption peaks corresponding to electronics transition from 3H6 to state to 5G5, 5G6, 1G4, 1G4, 5F3, 5F4, 5F5, 3F3, and 3H4 are shown. It is shown that absorption at 680 nm and 790 are insensitive to the addition of Ho2O3 in contrast to that at 580 nm and 650 nm.

Structural, dielectric and conductivity of multicomponent borotellurite glasses have been thorougly investigated. Noncrystallinity confirmed through XRD and structural units identified from FTIR spectra. Dielectric constant and loss decreased with increase of frequency and temperature. Polarization parameters such as molar volume, (Vm), molar refraction (Rm), molar polarizability (αm), electronic polarizability (αe) and metallization criterion (M) were determined. Power law behavior of ac conductivity has been verified and frequency exponent obtained. Activation energy of dc and ac conductivity obtained from Mott's small polaron hopping model fits and discussed. Frequency exponent decreased with temperature as predicted by correlated barrier hopping model. Hunt's model fit to conductivity data yielded similar frequency exponent values as obtained from power law. Linear relation between ac and dc conductivity has been observed as predicted by Barton, Nakajima and Namikawa theory. Time-temperature superposition principle has been verified by drawing master curves. [ABSTRACT FROM AUTHOR]

Borotellurite glasses of composition (0.4Li 2 O 0.4MgO)0.2TMO(1.4B 2 O 3 0.6TeO 2) with TMO: MoO 3 , WO 3 or Bi 2 O 3 were synthesized by standard melt quenching technique. The X-ray diffraction (XRD) technique confirmed the amorphous nature of the prepared samples. FTIR studies have explored the presence of structural units and bending vibrations. It was confirmed that the glassy matrix of these systems was based mostly on BO 3 /BO 4 units, and TeO 3 /TeO 4 units in less proportion. UV–vis spectroscopy was employed to examine some optical properties. Changes induced by the three transition metal oxides on the glassy matrix produce modifications in the optical band gap, Urbach's energy, refractive index and permittivity values, related to their different sizes regarding to their different ionic radius. A double analysis following the Tauc and the DASF methods confirms allowed direct inter-band electronic transitions in the studied glasses. In this work, we can observe that high values of density, high refractive index and high polarizability suggest that LMBT: Bi glass is suitable for activating with Dy3+ ions. • TMO (MoO 3 , WO 3 and Bi 2 O 3) improve the structure on the borotellurite glassy matrix. • LMBT:Bi exhibit high termal stability and is the most homogeneous glassy matrix. • Refractive index values for LMBT glasses are appropriate for use in w-LED. • LMBT:Bi is the best compound for activating with Dy3+ ions. [ABSTRACT FROM AUTHOR]

(80-x)B2O3-xTeO2-10Li2O-10Al2O3 (x = 10–60 mol%) glasses were prepared by a melt-quenching technique to investigate the effects of mixing B2O3 and TeO2 glass formers on DC conductivity and elastic properties of the glass system. The structural analysis revealed a competition between TeO2 and B2O3 formers, where, TeO4 functional group indicated bridging oxygen (BO) decreased with increasing TeO2 content, while BO4 units indicated BO fluctuated below 40 mol% prior to finally increasing which suggested that BO4 units became dominant above 40 mol% TeO2. At x = 40 mol% TeO2 content, the observed minima in the independent elastic moduli (longitudinal, CL and shear, μ) together with bulk, K, Young's and Y modulus was due to the presence of a high concentration of TeO3 and BO3 units indicating non-bridging oxygen (NBO). DC conductivity has also demonstrated a minimum at x = 40 mol% suggesting that the presence of MGFE contributed to the minima in elastic properties. [ABSTRACT FROM AUTHOR]

This work presents a study on the characteristics of the radiation attenuating behavior of oxy-fluoro borotellurite glasses with general formula TeO2–B2O3–LiF–BaO–Bi2O3. The mass attenuation coefficient (MAC) decreases pointedly as the energy goes up from 15 keV–0.15 MeV. The MAC for the tested samples lies within the range 40.032–50.170 cm2/g at 15 keV. We examined the effective atomic number (Zeff), and the results revealed that initially Zeff reaches the maximum values up to around 0.1 MeV and then Zeff decreases and reaches the minimum values between around 1 and 4 MeV. The Zeff lies within the range of 56.11–57.85 (at 15 keV). The Zeff of the tested samples increases with the increasing content of TeO2. The half value layer (HVL) was evaluated, and the effect of TeO2 and the energy on this parameter was discussed. The minimum HVL was reported at 15 keV and varied between 0.00463–0.00226 cm. [ABSTRACT FROM AUTHOR]

The borotellurite glasses whose chemical structure is (29.5–0.4x)CaO + 10CaF 2 + (60–0.6x)B 2 O 3 + xTeO 2 + 0.5Yb 2 O 3 (where x=10, 16, 22, 31, and 54 % mole. represent TCCBY1-TCCBY5, respectively) are Pb-free, thermally stable, and transparent glasses with attractive optical features for technological applications. The gamma-photons, electrons, protons, neutrons, carbon ions, fast neutrons, and fast neutron interaction parameters of these glasses are presented in this study to better understand the role of TeO 2 in influencing their radiation shielding properties and radiation protection applications. The photon mass attenuation coefficient was evaluated by XCOM computation and simulation using the FLUKA code. The FLUKA code was also used to evaluate the mass stopping powers of the charged radiations, while neutrons' cross sections were evaluated using standard expressions. For 0.015 MeV–15 MeV photons, the mass attenuation coefficients of the glasses fell from 17.9499 to 0.0246 cm2/g for TCCBY1, 20.5628 to 0.0263 cm2/g for TCCBY2, 23.2756 to 0.079 cm2/g for TCCBY3, 26.7487 to 0.0298 cm2/g for TCCBY4, and 33.3591 to 0.0335 cm2/g for TCCBY5. The photon half-value layer at 15 keV is reduced by about 19.57%, 32.68%, 48.84%, and 63.89% when the TeO 2 content increases from 10 mol to 16, 22, 31, and 54 mol, respectively. TeO 2 was found to suppress photon buildup in the glasses. The mass stopping powers of charged radiation increased as glass density decreased. The addition of TeO 2 into the glass structure increased the ability of the TCCBY glass to absorb fast neutrons by up to 54 % mole. The gamma radiation and fast neutron moderating ability of TCCBY5 glass compared to common shields and other materials is exceptional. The glass is recommended for the design of Pb-free, transparent, and efficient radiation protection structures. • Radiation shielding capacity of borotellurite glasses is estimated. • Monte Carlo simulations are carried out. • HVL is reduced by 63.89% at TeO 2 = 54 mol. • TCCBY5 glass system has a potential use in nuclear applications. [ABSTRACT FROM AUTHOR]

Six 1.0 mol% Er 2 O 3 -doped lead fluoride zinc borotellurite glasses comprising different alkali metal oxides and fluorides (K 2 O, Na 2 O, Li 2 O, KF, NaF, and LiF) have been synthesized via melting and quick-quench approach and structural, thermal, optical, chromatic, upconversion, and NIR (near-infrared) emission features and fluorescence decay times were explored. Main structural units BO 3 and BO 4 , as well as TeO 4 and TeO 3 , are affirmed in all glasses networks by Fourier transform infrared and Raman spectroscopy. For transition 4I 13/2 →4I 15/2 , σ emi (emission cross-section) has been assessed by applying Füchtbauer–Ladenburg and McCumber's theories. For Li 2 O and NaF constituting glasses, acquired peak absorption cross-section (4I 15/2 →4I 13/2) values are 0.999 × 10−20 cm2 and 1.093 × 10−20 cm2, while σ e m i M (4I 13/2 →4I 15/2) values are 1.064 × 10−20 cm2 and 1.174 × 10−20 cm2 individually. At various P (population inversion) values, calculated gain spectra revealed the C- band amplification from P = 40%. [ABSTRACT FROM AUTHOR]

• Optical and NIR luminescence features of Nd3+-doped borotellurite glasses are examined. • J-O parameters (Ω 2 , Ω 4 , and Ω 6) and radiative factors (A R , β R , β exp , and τ rad) are computed from absorption and emission spectra. • Nd3+:4F 3/2 emitting level decay curves are recorded under 808 nm LD excitation and analyzed. • 6.16 × 10‒21 cm2 & 53.68 nm are σ m a x e m i & Δλ eff of 4F 3/2 →4I 13/2 transition in Nd3+: Na glass (λ exci. = 584 nm). • 3.72 × 10‒21 cm2 & 51.62 nm are σ m a x e m i & Δλ eff of 4F 3/2 →4I 9/2 transition in Nd3+: K glass (λ exci. = 584 nm). Six 1.0 mol% Nd 2 O 3 -doped NaF+ZnO+BaO+TeO 2 +B 2 O 3 glasses containing single and mixed alkali oxides (K 2 O, Na 2 O, Li 2 O, K 2 O/Li 2 O, K 2 O/Na 2 O, and Na 2 O/Li 2 O) were prepared via melt-quenching approach and optical and NIR (near-infrared) emission traits including fluorescence decay times were explored. In all samples, Na ions comprising glass possesses 53.68 nm ∆λ eff (effective bandwidth), 6.16 × 10‒21 cm2 σ m a x e m i (peak emission cross-section), and 3.31 × 10‒26 cm3 σ m a x e m i × ∆λ eff (gain bandwidth) for transition 4F 3/2 →4I 13/2 for O-band amplification, and also owns larger σ m a x e m i , σ m a x e m i × ∆λ eff , and optical gain for 4F 3/2 →4I 11/2 for NIR lasing action at 1.06 μm. Further, K ions constituting glass holds larger full width at half maximum (= 46.23 nm) or better ∆λ eff (= 51.62 nm), moderate branching ratios (β R (= 42.37%) and β exp (= 19%)), and higher radiative decay time (= 662 μs) and τ meas (= 76.10 μs) for transition 4F 3/2 →4I 9/2 for ∼0.9 μm laser operation. [ABSTRACT FROM AUTHOR]

The glasses with the composition 20PbO-(10-x)CdO-10TeO -60B O -xCuO (0.5=x=2) were prepared by melt quenching technique. X-ray diffractograms revealed the amorphous nature of the glasses. Optical absorption spectra are recorded at room temperature. Optical band gap (E) and Urbach energies were determined. Electron Paramagnetic opt 2+ Resonance (EPR) studies were carried out by introducing Cu2+ as the spin probe. EPR spectra of all the glass samples were recorded at X-band (≈9.7 GHz) frequencies. From the EPR spectra spin-Hamiltonian parameters were evaluated. It -4 -1 -4 was observed that (g ≈2.360, g≈2.080) g >g >g (2.0023) and (A≈136x10 cm, A ≈30 x10-4 cm-1) A1 >A1. From these values it is concluded that the ground state of Cu2+ is (²Bfg) and the site symmetry around Cu ion was 1g tetragonally distorted in octahedral sites. It was observed that the intensity of the EPR spectra increases with increase of CuO concentration, which shows that more number of Cu ions are participating in the resonance. The optical absorption spectra revealed broad absorption band, which is assigned to transition. From the EPR and Optical 1g 2g data bonding coefficients were evaluated and discussed. [ABSTRACT FROM AUTHOR]

Borotellurite glasses in the composition, (B 2 O 3 ) 0.2 –(TeO 2 ) 0.3 –(CoO) x –(Li 2 O) 0.5-x ; x = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45 and 0.50 have been synthesized and their non-crystalline nature confirmed by XRD. Density of the glasses increased and molar volume decreased up to x = 0.3 and reversed their trends for x > 0.3. The glass transition temperature is increased up to x = 0.30 and decreased for x > 0.3. Changes in density, molar volume and glass transition temperature around x = 0.3 may be ascribed to structural/topological modifications occurring in the glasses. Polaron parameters have been determined. Thermal stability is found to increase with increasing x. Activation energy for dc conduction at high temperature has been determined by applying Mott's small polaron hopping model. Conductivity and activation energy were found to pass through minimum and maximum respectively for x around 0.30, which may be due to a changeover of conduction mechanism from predominantly ionic regime to electronic regime. This transition can be attributed to the interaction between electrons and alkali ions. This result is of significance both scientifically and technologically. Mott's variable range hopping model has been employed to understand conductivity at low temperature for the present glasses. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis and the characterization of Yb 3 + -doped calcium borotellurite (CaBTeX) glasses with composition 10CaF 2 –(29.5 − 0.4x)CaO–(60 − 0.6x)B 2 O 3 –xTeO 2 –0.5Yb 2 O 3 (x = 10, 16, 22, 31 and 54 mol%). The results of XRD confirm the amorphous character of all the samples. The density, molar volume, refractive index and electronic polarizability values show an increase with TeO 2 content. Otherwise, the optical band gap energy shows a decrease with the increase of TeO 2 content. The replacement of CaO and B 2 O 3 by TeO 2 changes the glass structure, which decreases the excited Yb 3 + /cm 3 and, consequently, the luminescence intensity. The temperature dependence of luminescence was studied for all the samples up to 420 K. The fluorescence lifetime does not change significantly due to TeO 2 addition. In addition, absorption and emission cross section were calculated and present high values as compared to other tellurite and phosphate glasses. [ABSTRACT FROM AUTHOR]

Ternary lithium borotellurite glasses of composition(Li 2 O) y [(2TeO 2 ) x -(B 2 O 3 ) 1 − x ] (1 − y ) ( y = 0.33 and 0.40; and 0 ≤ x ≤ 1) reveal a negative network former mixing effect, implying that their electrical conductivities and ionic mobilities are lower than those expected by linear interpolation between their binary endmembers. For the y = 0.33 system, the room temperature ionic conductivity decreases from ~ 10 − 8 (Ω·cm) − 1 to 10 − 11 (Ω·cm) −1 , while the activation energy increases from ~ 0.7 to 1.0 eV with increasing tellurium content. The structural foundations of the network former mixing effect have been probed by multinuclear solid state NMR spectroscopy. Static 125 Te NMR spectra can be modeled by considering inhomogeneous broadening due to the chemical shift anisotropy effects, subject to Gaussian distributions of principal tensor values. The lineshape parameters are only weakly dependent on glass composition. 11 B magic angle spinning (MAS)-NMR studies reveal that the fraction of four-coordinate boron species, B (4) , increases moderately with increasing tellurium content. Overall, the data suggest that the concentration of heteroatomic connectivities is relatively low, suggesting chemical segregation and/or incipient phase separation into binary lithium tellurite and lithium borate units at the atomic- or the nanoscale. Static 7 Li NMR spectra at low temperatures are governed by the strength of homonuclear 7 Li 7 Li and heteronuclear 7 Li 11 B/ 7 Li 10 B magnetic dipole-dipole interactions. Considering the second moments for the dipolar magnetic interactions in the lithium-diborate model compound, the second moments of the 7 Li NMR lineshapes could be successfully modeled by a random spatial distribution of the Li + ions. Phenomenological modelling of the motional narrowing effects observed with increasing temperature results in a consistent description of the negative network former mixing effects in terms of activation energies and dynamic heterogeneities. The negative network former mixing effects is stronger in the system with lower lithium ion content ( y = 0.33). [ABSTRACT FROM AUTHOR]

In this study, 10CaF 2 – (29.9–0.4x)CaO – (60-0.6x)B 2 O 3 – xTeO 2 – 0,1Er 2 O 3 (x = 10, 16, 22, 30 and 50 mol %) glasses were synthesized, and their optical and spectroscopic properties were investigated. X-ray diffraction, density, glass transition temperature (Tg), crystallization temperature (Tx), refraction index, luminescence, radiative lifetime and optical absorption measurements were carried out. Molar volume ( V m ), thermal stability (Tx-Tg), electronic polarizability ( α m ), optical bang gap energy ( E g ) and Judd-Ofelt (JO) parameters Ω t (2,4,6) were also calculated. The results are discussed in terms of tellurium oxide content. The increase of TeO 2 in the glasses composition increases density, refractive index and electronic polarizability. The optical band gap energy decreases varying from 3.37 to 2.71 eV for the glasses with 10 and 50 mol% of TeO 2 , respectively. The optical absorption coefficient spectra show characteristic bands of Er 3+ ions. Furthermore, these spectra in NIR region show a decrease of hydroxyl groups as a function of TeO 2 addition. Luminescence intensity and radiative lifetimes at 1530 nm show an increasing with the TeO 2 content. The JO parameters of Er:CaBTeX glasses follow the trend Ω 2 > Ω 4 > Ω 6 and the quality factor values (Ω 4 /Ω 6 ) were between 1.37 and 3.07. By comparing the measured lifetime with the calculated radiative decay time, quantum efficiency was calculated. The luminescence emission intensity at 1530 nm decreases with the increase of temperature. The lifetime values show a slight trend to decrease with the temperature increase, from 300 to 420 K, for all the samples. [ABSTRACT FROM AUTHOR]

Borotellurite glasses containing different rare-earth (RE) ions (Er, Tm, and Pr) with the nominal composition (50–x) B 2 O 3 –10 TeO 2 –10 MoO 3 –10 ZnO–10 Na 2 O–10 SrO–(x) Er 2 O 3 /(x) Tm 2 O 3 /(x) Pr 2 O 3 (x = 0, and 1.0 mol%) were prepared by the melt quenching technique. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements confirm the amorphous nature for the prepared glasses and energy dispersive X-ray analysis (EDAX) confirms that all the elements present in the respective glasses. The presence of various functional groups such as O B O bond bending vibrations and specific vibrations of Na + , and Sr 2 + bonds, vibrations of metal cations such as Zn 2 + , B O stretching vibrations of the BO 4 tetrahedral units, stretching vibrations of B O bonds of pyroborate groups, vibrations due to BO 2 O − triangles linked with BO units, stretching vibrations of B O bonds involving nonbridging oxygen (NBO) and being part of a boron-oxygen network, alkali or alkaline tetra borate groups, isolated diborate groups, pentaborate, tetraborate and diborate units, symmetric bending vibrations of TeO 4 tbps and symmetric stretching of the Te eq O ax Te bond, stretching and bending vibrations of Te O Te linkages in TeO 4 (tbps), TeO 3 + 1 polyhedra and TeO 3 (tps), and stretching vibrations of Mo O Mo linkages or vibrational modes of MoO 4 2 − tetrahedral units including stretching vibrations of ZnO 4 − structural units, and non-hygroscopic nature of the glasses are confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Raman spectra, respectively. The thermal properties of the glasses were studied by simultaneous thermal analysis (STA) technique and from the differential scanning calorimetry (DSC) profiles the glass transition temperature (T g ), onset crystallization temperature (T x ), and crystallization temperature (T c ) are identified and from these values, the calculated thermal stability values are varied in the temperature range 88–103 °C with different rare earth ions incorporation. From the measured optical absorption spectrum of the host glass, direct and indirect optical band gap energies were evaluated and the values of indirect optical band gap energies calculated from the absorption spectrum (E opt ) matches well with the values of optical band gap energies (E opt asf ) calculated from absorption spectrum fitting (ASF) method, and the glass has Urbach energy value 0.627 eV. The fundamental absorption edge wavelength (λ edge ) shows red-shift with RE ions doping into the host glass due to the formation of non-bridging oxygens. [ABSTRACT FROM AUTHOR]

CoO and LiO mixed with borotellurite glasses in the compositions, (BO)-(TeO)-(CoO)-(LiO), where x = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, and 0.50 were synthesized by fast cooling the melt to room temperature. Absence of crystalline phases in the samples was confirmed by X-ray diffraction studies. Changes in dielectric properties with frequency and temperature over wide ranges have been measured. Dielectric constant and loss increased with increase in CoO content. AC conductivity has been analyzed using Mott's small polaron model and activation energy was determined. Activation energy decreased and conductivity increased with increase in CoO content up to 0.3 mole fractions, and they behaved oppositely for higher concentration of CoO. This observed change of trend in activation energy and conductivity at 0.3 mole fraction of CoO ascribed to switch over of conduction mechanism occurring from predominantly ionic to electronic regime. For the first time, a transition of conduction mechanism is observed in borotellurite glasses. Temperature and composition independent relaxation mechanism in these glasses has been confirmed by plotting the scaled conductivity master curves. Hunt's model has been invoked to understand the frequency dispersion of conductivity. [ABSTRACT FROM AUTHOR]

Zinc borotellurite glasses doped with lanthanum oxide were successfully prepared through melt-quenching technique. The amorphous nature of the glass system was validated by the presence of a broad hump in the XRD result. The refractive index of the prepared glass samples was calculated by using the equation proposed by Dimitrov and Sakka. The theoretical value of molar refraction, electronic polarizability, oxide ion polarizability and metallization criterion were calculated by using Lorentz-Lorenz equation. Meanwhile, expression proposed by Duffy and Ingram for the theoretical value of optical basicity of multi-component glasses were applied to obtain energy band gap based optical basicity and refractive index based optical basicity. The optical basicity of prepared glasses decreased with the increasing concentration of lanthanum oxide. Metallization criterion on the basis of refractive index showed an increasing trend while energy band gap based metallization criterion showed a decreasing trend. The small metallization criterion values of the glass samples represent that the width of the conduction band becomes larger which increase the tendency for metallization of the glasses. The results obtained indicates that the fabricated glasses have high potential to be applied on optical limiting devices in photonic field. [ABSTRACT FROM AUTHOR]

Borotellurite glasses with formula 60BO−10ZnO−(30 − x)NaF− xTeO ( x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density ( ρ) was determined by the Archimedes method at room temperature. The density ( ρ) and molar volume ( V ) were found to increase with increasing TeO content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivity ( σ ) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO content from 0 mol.% to 15 mol.%. [ABSTRACT FROM AUTHOR]

In this work, the glass formation in Calcium Borotellurite (CBTx) system and their optical properties were studied. Six glass samples were prepared by melt-quenching technique and the samples obtained are transparent, lightly yellowish, without any visible crystallites. The results showed that TeO 2 addition increases the density, the electronic polarizability and, consequently, the refractive index. The increase of electronic polarizability and optical basicity suggest that TeO 2 addition increases the non-bridging oxygen (NBO) concentration. The increase of TeO 2 shifts the band edge to longer wavelength owing to increase in non-bridging oxygen ions, resulting in a linear decrease of optical energy gap. The addition of TeO 2 increases the temperature coefficient of the optical path length (dS/dT) in room temperature, which are comparable to phosphate and lower than Low Silica Calcium Alumino Silicate (LSCAS) glasses. The values of dS/dT present an increase as a function of temperature for all the samples measured. The results suggest that CBTx is a good candidate for rare-earth doping and several optical applications. [ABSTRACT FROM AUTHOR]

This research reports the optical and luminescence properties of new tellurite glass system with nominal composition of x (Sm 2 O 3)–10MgO–30B 2 O 3 −(60− x)TeO 2 , where x = 0, 0.5, 1.0, 2.0 and 3.0 mol% synthesized via fast cooling melt-quenching method. The physical characteristic, UV–visible, refractive index, and photoluminescence spectroscopy techniques were used to examine the structural changes and optical performance of the glasses. No sharp peak appeared in the diffraction of XRD region proved the amorphous state of the glasses. The bulk density of the prepared glass samples presented an increasing trend from 4.105 to 4.403 g/cm3 meanwhile the molar volume showed opposite pattern with range value of 28.69–29.39 cm3/mol. The highest density governed by glass sample with concentration of samarium ions at 3.0 mol%, which is 4.403 g/cm3. The optical absorption spectra were characterized to determine the energy band gap, Urbach energy, and refractive index of the glasses. The obtained values for refractive index is in between 2.481 and 2.575 meanwhile for Urbach energy is 0.238–0.319 eV. The optical absorption spectra reveal eleven energy transitions bands centered at 4G 9/2 , 4I 11/2 , 4F 3/2 , 4G 5/2 , 6F 11/2 , 6F 9/2 , 6F 7/2 , 6F 5/2 , 6F 3/2 , 6H 15/2 , 6F 1/2 from ground state of 6H 5/2. Four strong emission peaks occurred in photoluminescence, with the highest red emission peak at 600 nm. Chromaticity coordinates of the glass samples were determined as well as the dominant wavelength and colour purity, using CIE Chromaticity diagram 1931. • New tellurite glass series (60- x)TeO 2 –30B 2 O 3 –10MgO- x (Sm 2 O 3) have been successfully fabricated. • The density increase with the increase of samarium concentration. • The transitions from 6H 5/2 state to 6H, 6F, and 4I follow the energy selection rule. • The optical band gap increase in the range of 2.415 eV–2.706 eV and 2.892 eV–2.979 eV for both transition. • Glass sample MBTGSm-2.0 produce the highest red emission intensity. [ABSTRACT FROM AUTHOR]

This paper reports the influence of bismuth ions (Bi+) on photoluminescence properties of Tm 2 O 3 doped borotellurite based glasses (BTGS) with the composition (64-y)B 2 O 3 –30TeO 2 – 5NaF- yBi 2 O 3 –1Tm 2 O 3 , where y = 0, 4, 8, 12 and 16 wt% for the near-infrared (NIR) emission applications. All glasses were prepared using the melt-quenching method and confirmed to exhibit amorphous nature by the X-ray diffraction (XRD) technique. The absorption spectra in the wavelength range of 300–2100 nm and emission spectra in the wavelength range of 400–2200 nm were studied. Increase of y wt. % value increases the 3H 4 →3F 4 and 3F 4 →3H 6 (near-infrared, NIR emission) intensities due to cross-relaxation (CR) and enhanced energy transfer processes between the active centres (Bi+ and Tm3+ ions), which are strongly influenced by bismuth content (Bi+) in the glass matrix. Based on Judd-Ofelt theory, the intensity parameters Ω 2 , Ω 4 and Ω 6 for each glass were determined and found to follow the trend Ω 2 >Ω 4 >Ω 6 similar to the recently reported photonic glasses. Using the Ω λ parameters and reduced matrix elements, the calculation for the emission transition probability (A), radiative lifetime (τ R), branching ratio (β R) and emission-cross sections (σ P E) of 3H 4 , 3H 5 , and 3F 4 energy levels were done and found to be slightly higher than fluoride and other oxide-based glasses because of the high density and refractive index values of the present samples. • Glass compositions (64-y)B 2 O 3 –30TeO 2 –5NaF-yBi 2 O 3 –1Tm 2 O 3 , where y = 0, 4, 8, 12 and 16 wt%, were synthesized using melt-quench method. • The absorption and emission spectra of the glasses were recorded and analysed. • Judd-Ofelt and radiative parameters of the glasses have been evaluated. • Cross-relaxation and enhanced energy transfer processes between bismuth and thulium ions were discussed. [ABSTRACT FROM AUTHOR]

This study aimed to investigate a specific lithium-fluoro borotellurite glass system based on (60-x)B 2 O 3 -xTeO 2 -5LiF–5BaO–5Bi 2 O 3 (x = 25, 35, 45, 55, 65, 75, and 85 mol %) composition encoded as BTLBB1- BTLBB7 in terms of their optical, mechanical characteristics, and gamma ray attenuation competencies. The Rmolar possess the values 22.064, 21.546, 21.038, 20.860, 19.998, 18.936, and 20.024 (cm3/mol), while the αmolar possess the values 8.755, 8.550, 8.348, 8.278, 7.936, 7.514, and 7.946 (cm3) for BTLBB1, BTLBB2, BTLBB3, BTLBB4, BTLBB5, BTLBB6, and BTLBB7, respectively. Values of χ(3) were 5.189 × 10−12, 5.150 × 10−12, 4.995 × 10−12, 4.448 × 10−12, 4.624 × 10−12, 4.995 × 10−12, and 5.812 × 10−12 (esu), while values of n 2 o p t i c a l were 7.821 × 10−11, 7.768 × 10−11, 7.558 × 10−11, 6.813 × 10−11, 7.054 × 10−11, 7.558 × 10−11, and 8.656 × 10−11 for BTLBB1, BTLBB2, BTLBB3, BTLBB4, BTLBB5, BTLBB6, and BTLBB7, respectively. The highest μ m values were found for BTLBB7 glass sample (TeO 2 = 85 mol%) and obey the trend: (μ m) BTLBB7 > (μ m) BTLBB6 > (μ m) BTLBB5 > (μ m) BTLBB4 > (μ m) BTLBB3 > (μ m) BTLBB2 > (μ m) BTLBB1. The T 1/2 values were reported as 0.105 cm, 0.092 cm, 0.082 cm, 0.075, 0.067, 0.058 and 0.057 cm for those BTLBB1, BTLBB2, BTLBB3, BTLBB4, BTLBB5, BTLBB6 and BTLBB7 at 0.1 MeV photon energy, respectively. The BTLBB7 sample has the highest overall effective atomic numbers Z eff (55.04), while BTLBB1sample has the lowest values (50.33) at 0.1 MeV photon energy. The BTLBB1sample was reported the maximum EBF and EABF values, while the minimum values were reported for the BTLBB7 sample. The investigated glasses can be used as good candidate for optical fibers, photonic devices, and superior in terms of gamma-photon attenuation capability. • Samples of lithium-fluoro borotellurite glasses were chosen. • Optical and mechanical properties were investigated. • γ-ray attenuation properties have been examined. • Glasses can be used as good candidate for optical applications. • Glasses are superior in terms of gamma-photon attenuation capability. [ABSTRACT FROM AUTHOR]

A new series of Er3+ ions doped Oxy Chloro Boro Tellurite glasses were prepared by melt-quenching method. Various spectroscopic properties were determined from absorption, excitation and photo-luminescence spectra. The Judd-Ofelt intensity parameters Ω λ (λ=2,4,6) were estimated based on absorption spectra. A strong luminescence band was observed at 1536nm under the excitation wavelength of 522nm. The gain coefficient of 1.53μm emission was estimated to probe the utility of glasses in broad band amplification technology. Inokuti-Hirayama model was employed to decay curves, to comprehend the nature of energy transfer between erbium ions. The stimulated emission cross-sections (σ sec), branching ratios (β R), quantum efficiencies (η%) and gain cross-section (σ sec xτ R) for Er3+ ions doped OCBT glasses were evaluated and compared with other reported glass samples. Based on the highest stimulated emission cross-section, branching ratios, quantum efficiencies and gain cross-sections, it is suggested that 1mol% of Er3+ ions doped OCBT glass is more suitable for NIR region optical device applications. • Er3 doped OCBT glasses were prepared by melt quenching method. • mol% of Er3+ ions in OCBT glasses is optimum for maximum intensity. • A strong NIR emission band is observed around 1536 nm. • OCBTEr1.0 glass is useful for solid state NIR lasers and EDFA applications. [ABSTRACT FROM AUTHOR]

In the present report, erbium doped zinc borotellurite glasses were irradiated with 50 kGy gamma radiation using a60Co radioisotope source. The effect of gamma irradiation on the physical, structural, optical and spectroscopic properties of erbium doped zinc borotellurite glasses was studied. Also the shielding properties of the un-irradiated glasses were studied with the help of Phy-X/PSD software. The gamma irradiation caused some structural changes as indicated by FTIR and Raman studies which may be due to the formation of the new structural units. Its influence on the optical properties like band gap (direct and indirect band gap), Urbach energy and refractive index were analyzed with the help of UV–Vis–NIR spectrometer. The UV–Vis–NIR absorption spectra showed increase in absorption after the gamma irradiation. The optical band gap value decreased for the irradiated samples. The spectroscopic properties such as stimulated emission cross-section, bandwidth, lifetime etc. Got marginally modified due to gamma irradiation. The shielding properties of the un-irradiated glasses were improved with the increasing rare earth concentration. The glasses with rare earth doping showed less changes in their properties after gamma irradiation which indicates that these glasses are more resistant to gamma radiation as compared to the base glass. [Display omitted] • The Er3+-doped zinc borotellurite glasses were further subjected to 50 kGy gamma ray dose using a60Co radioisotope. • The effect of gamma irradiation on the structure was found to be more dominant in the undoped sample then the doped sample. • The spectroscopic properties of the glasses were slightly modified by the irradiation. • The shielding properties of the glasses were improved after rare earth doping. [ABSTRACT FROM AUTHOR]

Dy3+, Eu3+ co-doped borotellurite (HKMTZ) glasses are fabricated successfully by pressureless solid-phase reaction for potential applications in white light-emitting diodes (WLED). A novel effect of individual emission of dual-modes between Dy3+ and Eu3+ is observed firstly which reveals the multicolor mechanism that can be tuned easily from reddish-orange (2746 K) to nature-white (4588 K) to cool white (7889 K). And dual-modes emissions of Dy3+ and Eu3+ with independent light-emitting are enabled to be observed under 393 nm excitation due to the strong competition between Dy3+ and Eu3+. Moreover, replacing traditional packaging technology of LED to regard as color-converter has been come up as an efficient method to promote properties of luminescence and thermal stability. The aforesaid phenomena of photoluminescence results demonstrate that Dy3+, Eu3+ co-doped HKMTZ glass is an excellent candidate with tunable multicolor which may possess promising applications for WLED. [Display omitted] • Dy3+, Eu3+ doped HKMTZ glasses are fabricated by solid-phase method as WLED material. • A novel effect of individual emission of dual-phase is identified between Dy and Eu. • Multicolor regulation can be tuned from reddish-orange to nature-white to cool white. • HKMTZ glasses can emit superior white illumination under UVB and UVC excitation. • New research effect for multicolor tuning WLED provides a new dimension of thinking. [ABSTRACT FROM AUTHOR]

A set of WO 3 doped zinc-lithium-dysprosium-borotellurite glasses in the compositions, (B 2 O 3) 0.2 –(TeO 2) 0.3-x –(ZnO) 0.28 –(Li 2 CO 3) 0.2 –(Dy 2 O 3) 0.02 –(WO 3) x ; x = 0.02 to 0.12 (labeled as W1, W2, W3, W4, W5 and W6 respectively) have been synthesized. Amorphous nature of the samples has been confirmed and density measured. Molar volume, oxygen packing density and field strength were determined. Optical absorption spectra were recorded. Band gap values are found to increase with WO 3 content up to 0.08 mol fractions and decreases for further amounts of WO 3. Urbach energy behaved in the opposite fashion to that of band gap with WO 3 content. These results are attributed to bonding defects and the number of non-bridging oxygen. Refractive index, molar refractivity, molar electronic polarizability, reflection loss, metallization ratio, oscillator strengths and Judd-Ofelt (J-O) intensity parameters have been determined. Based on the observed trends of JO intensity parameters, lasing ability of the glasses and their optical quality has been discussed. Photoluminescence (PL) spectra have been recorded and they exhibited three bands namely, 4F 9/2 → 6H 15/2 (blue), 6H 13/2 (yellow) and 6H 11/2 (red). The observed ratio of intensity of yellow to blue band inferred that asymmetry around rare earth ions decreases with increase of WO 3 content. Using PL decay profiles, the lifetime (τ exp) for yellow emission has been determined. Using the values of τ exp and estimated radiative lifetime (τ R) , the quantum efficiency (η) has been determined and for 4F 9/2 → 6H 13/2 transition and, it is found to be in the range from 43% to 67% for the present glasses. Based on JO parameters, quantum efficiency and other radiative parameters, W4 glass is proposed for lasing in yellow region. For the first time, effect of WO 3 on the optical properties of zinc-lithium-dysprosium-borotellurite glasses has been thoroughly investigated. Image 1 • Borotellurite glasses mixed with ZnO, Li 2 O, Dy3+ and WO 3 were synthesized. • Increase in density, OPD etc., revealed increase in compactness of net work. • Optical band gap increased with WO 3 content up to 0.08 mole fractions and decreased for amounts. • Based on JO parameters, four of the present glasses are judged to be of good optical quality. • Based on quantum efficiency and other quantities, one of the glasses is proposed for yellow lasing. [ABSTRACT FROM AUTHOR]

Mixed glass former of composition 70 x TeO 2 +(1- x)B 2 O 3 +15Na 2 O+15K 2 O where x = 0–0.7 mol% have been prepared by melt quenching method to investigate their structural, AC conductivity, and dielectric properties. The variation of conductivity (σ′) with TeO 2 showed a non-linear behaviour, where decrease to a minimum value at x = 0.4 mol% before increasing for x > 0.4 mol%. The minimum is suggested to be due to the low migration of Na+ and K+ ions caused by the mixed glass former effect (MGFE). Meanwhile, dielectric constant (ε′) showed a slight increase for x ≤ 0.4 mol% followed by a large increase for x ≥ 0.5 mol% TeO 2. The large increase in dielectric constant (ε′) for x ≥ 0.5 mol% is suggested to be due to the presence of some crystalline phase within the amorphous matrix. Structural analysis of the present glass system reveals N 4 reached minima at x = 0.2 mol% and 0.4 mol% with addition of TeO 2 which attributed to the structural changes due to the conversion of BO 4 to BO 3 units. Glass transition temperature, T g exhibited a non-linear increase for x ≤ 0.5 mol% followed by a large increase at x > 0.5 mol%. The conduction mechanism at low frequency region was found to be Inverse – Overlapping Large Polaron Tunnelling (Inverse – OLPT) for x ≤ 0.5 mol%, while the mechanism transformed to the OLPT model for x = 0.7 mol%. The electric modulus of the present glass system showed an asymmetric peak of M' , that reflected a non-Debye type relaxation. Image 1 • AC conductivity and dielectric properties of 70[xTeO 2 +(1-x)B 2 O 3 +15Na 2 O+15K 2 O glasses were studied. • N 4 values reached minima at x = 0.2 mol% and 0.4 mol% which attributes to the structural changes due to the conversion of BO 4 into BO 3 units. • AC conductivity minimum at x = 0.4 mol% was attributed to mixed glass former effect (MGFE). • Improved dielectric properties with increase in TeO 2 content. [ABSTRACT FROM AUTHOR]

Glasses with chemical composition {[(TeO₂) 0.7 (B₂O₃) 0.3 ] 0.8 [SiO₂] 0.2 } 1-x {Sm₂O₃ NPs} x where x = 0.01 to 0.05 molar fraction have been fabricated using conventional melt-quenching method. Fourier transform infrared (FTIR) spectra reveal the presence of TeO 3 , SiO 2 and BO 3 structural units in the glass network. The existence of samarium oxide nanoparticles was recorded through high resolution transmission electron microscopy (HR-TEM) with particle size of 71.74 nm. Meanwhile, the optical properties of fabricated samples were determined by UV–vis analysis. The variation in the optical band gap identifies the modification in the glass network to the formation of bridging oxygen (BO) and non-bridging oxygen (NBO). Other optical parameter including refractive index, Urbach energy, electronic polarizability, oxide ion polarizability and optical basicity were determined. The metallization criterion values obtained is in the range of 0.403 to 0.409, which suggest that the glass material has a huge potential applications, in non-linear optics fields. [ABSTRACT FROM AUTHOR]