Gamma-ray shielding and structural properties of barium-bismuth-borosilicate glasses

Niobium-containing tellurite glass with starting composition of (90 − x)TeO2–10Nb2O5–(x)ZnO (x = 0–15 mol%) have been prepared by melt-quenching method and the effect of reduction of TeO2 with simultaneous increase in ZnO on elastic properties was studied. Ultrasonic longitudinal and shear velocity showed initial decrease of 3.52% and 2.37%, respectively, at x = 5 mol%. For x > 5 mol%, longitudinal velocity showed weak recovery but shear velocity showed steady recovery with ZnO and recorded 0.95% increase in value at x = 15 mol% compared to x = 0 sample. Shear and Young's moduli recorded similar drop at x = 5 mol% followed by strong recovery at x > 5 mol%, while longitudinal and Bulk modulus showed weak and no recovery, respectively, with x. Infrared (IR) absorption spectra showed increase in intensity of NbO6-assigned peak accompanied by increase in intensity of ZnO4 tetrahedra and TeO4 trigonal bipyramid (tbp) assigned peaks indicating formation of both non-bridging oxygen, NBO and bridging oxygen, BO, respectively, with addition of ZnO. The initial drop in ultrasonic velocity and related elastic moduli observed at x = 5 mol% indicates weakening of network rigidity of the glass system due to structural modification as a direct effect of TeO2 reduction and existence of NBO. However, further replacement of TeO2 by ZnO at x > 5 mol% contributed to increase in BO causing rigidity of the glass network to improve. In addition, hardness, H, was observed to increase with ZnO indicating increase in connectivity of the glass network while Poisson's ratio, σ, decreased indicating increase in cross-link density of the glass system. The combined results of ultrasonic velocity and IR absorption spectra suggest that the role of TeO2 is very critical in the ternary glass system as, although ZnO addition showed improved rigidity due to recovery of shear modulus, the weakening of longitudinal and Bulk moduli indicates ZnO is not fully effective as glass former in place of TeO2.

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Effects of concurrent TeO2 reduction and ZnO addition on elastic and structural properties of (90 − x)TeO2–10Nb2O5–(x)ZnO glass

The effect of MoO3 addition on the crystallization characteristics of 2Al2O3–23Li2O–(75 − x) B2O3 glass (where x MoO3 = 0, 10, 20, and 40 mol %) has been investigated The compositional dependence of the glass transition (T
 g), and crystallization (T
 c) temperatures was determined by the differential thermal analysis (DTA) It was found that both the T
 g and T
 c decrease with increasing MoO3 content The amorphous nature of the as-quenched glass and crystallinity of the produced glass–ceramics were confirmed by X-ray powder diffraction (XRD) analysis Glass–ceramics embedded with diomignite (lithium diborate, Li2B4O7) were produced from all investigated glasses by heat-treating the as-quenched glasses at the appropriate temperatures obtained from the DTA traces Addition of MoO3 to the glass composition at 10% MoO3, causes the formation of lithium molybdenum oxide (Li4MoO5) crystalline phase in addition to the diomignite phase Increasing MoO3 content to 20% causes a phase transformation of lithium molybdenum oxide from the (Li4MoO5) to the (Li2MoO4) phase and the formation of another lithium borate (Li4B2O5) phase in addition to the diomignite Further increase of MoO3 content to 40% results in another phase transformation to the lithium aluminum molybdenum oxide [LiAl(MoO4)2], and, in this case, the molybdenum content was excess enough to crystallize the molybdate (MoO3) itself Scanning electron microscopy (SEM) was used to characterize the morphology and microstructure of the formed solid solution phases The values of the T
 g decrease with increasing the MoO3 content The ultrasonic wave velocities and elastic moduli were determined using the pulse-echo method Both velocities (v
 L and v
 T) were increased as the MoO3 content, this increase can be attributed to the higher bond strength of Mo–O (607 kJ mol−1) than that of B–O (392 kJ mol−1)

Studying effect of MoO 3 on elastic and crystallization behavior of lithium diborate glasses

Optical and infrared absorption spectra of 3d transition metal ions-doped sodium borophosphate glasses and effect of gamma irradiation.

The Dy 3+ doped Zinc borophosphate glasses with the chemical composition (79- x )B 2 O 3 + x P 2 O 5 +10Li 2 O+10ZnO+1Dy 2 O 3 (where x =0, 10, 20, 30 and 50 in wt%) have been prepared by melt quenching technique. The prepared glass samples were characterized through optical absorption, emission and decay measurements. The bonding parameters, optical band gap and Urbach's energy values were calculated from the optical absorption spectra to explore the bonding nature of the Dy–O metal ligand and electronic band structure of the studied glasses. Judd–Ofelt ( JO ) intensity parameters were calculated from the absorption spectra by using the JO theory and it gives information about symmetry of the ligand environment around the Dy 3+ ion site. The Y / B intensity ratio and radiative properties were obtained from the emission spectra and the results were compared with the reported literature. The x , y chromaticity color coordinates of the studied glasses were analyzed using a CIE 1931 color chromaticity diagram and found that the x , y coordinates lie in the white light region. The decay curve measurements of the prepared glasses exhibit non-exponential behavior and are well fitted to Inokuti–Hirayama (IH) model to understand the energy transfer mechanism between Dy 3+ ions. The Q , R 0 and C DA values of the prepared Dy 3+ doped glasses were obtained from the IH model and the results were discussed and compared with the reported literature.

White light simulation and luminescence studies on Dy3+ doped Zinc borophosphate glasses

Glasses in the system (95−x) [0.25 Na2O–0.75 B2O3]–x P2O5–5 Fe2O3 (0⩽x⩽15 mol%), have been prepared by the melt quenching technique. Elastic properties and FT-IR spectroscopic studies have been employed to study the role of P2O5 on the structure of the glass system. Elastic properties Poisson's ratio, micro-hardness and Debye temperature have been investigated using sound wave velocity measurements at 4 MHz (both longitudinal and shear) at room temperature. The results showed that the density and the molar volume increase as both sound velocities and the determined glass transition temperatures decrease with increasing the contents of P2O5. Infrared spectra of the glasses reveal that the borate network consists of diborate units and is affected by the increase in the concentration of P2O5 content as a second network former. These results are interpreted in terms of the replacement of the diborate units with B–O–B bridges by phosphate units with non-bridging oxygens (NBOs). Therefore, the elastic moduli are observed to decrease with the increase in P2O5 content.

M.M. Mekawy

Papers

Structural studies of some phospho-borate glasses using ultrasonic pulse–echo technique, DSC and IR spectroscopy