Abstract: Makishima and Mackenzie model was used to
simulation of acoustic properties (longitudinal and shear ultrasonic
wave velocities, elastic moduli theoretically for many tellurite and
borate glasses. The model was proposed mainly depending on the
values of the experimentally measured density, which are obtained
before. In this search work, we are trying to obtain the values of
densities of amorphous glasses (as the density depends on the
geometry of the network structure of these glasses). In addition, the
problem of simulating the slope of linear regression between the
experimentally determined bulk modulus and the product of packing
density and experimental Young's modulus, were solved in this
search work. The results showed good agreement between the
experimentally measured values of densities and both ultrasonic wave
velocities, and those theoretically determined.
Abstract: The changes of the optical and structural properties of
Bismuth-Boro-Tellurite glasses pre and post gamma irradiation were
studied. Six glass samples, with different composition [(TeO2)0.7
(B2O3)0.3]1-x (Bi2O3)x prepared by melt quenching method were
irradiated with 25kGy gamma radiation at room temperature. The
Fourier Transform Infrared Spectroscopy (FTIR) was used to explore
the structural bonding in the prepared glass samples due to exposure,
while UV-VIS Spectrophotometer was used to evaluate the changes
in the optical properties before and after irradiation. Gamma
irradiation causes profound changes in the peak intensity as shown by
FTIR spectra which is due to the breaking of the network bonding.
Before gamma irradiation, the optical band gap, Eg value decreased
from 2.44 eV to 2.15 eV with the addition of Bismuth content. The
value kept decreasing (from 2.18 eV to 2.00 eV) following exposure
to gamma radiation due to the increase of non-bridging oxygen
(NBO) and the increase of defect in the glass. In conclusion, the glass
with high content of Bi2O3 (0.30Bi) give smallest Eg and show less
changes in FTIR spectra after gamma irradiation which indicate that
this glass is more resistant to gamma radiation compared to other
glasses.
Abstract: Series of tellurite glass of the system 78TeO2-10PbO-
10Li2O-(2-x)Nd2O3-xEr2O3, where x = 0.5, 1.0, 1.5 and 2.0 was
successfully been made. A study of upconversion luminescence of
the Nd3+/Er3+ co-doped tellurite glass has been carried out. From
Judd-Ofelt analysis, the experimental lifetime, exp. τ of the glass
serie are found higher in the visible region as they varies from
65.17ms to 114.63ms, whereas in the near infrared region (NIR) the
lifetime are varies from 2.133ms to 2.270ms. Meanwhile, the
emission cross section,σ results are found varies from 0.004 x 1020
cm2 to 1.007 x 1020 cm2 with respect to composition. The emission
spectra of the glass are found been contributed from Nd3+ and Er3+
ions by which nine significant transition peaks are observed. The
upconversion mechanism of the co-doped tellurite glass has been
shown in the schematic energy diagrams. In this works, it is found
that the excited state-absorption (ESA) is still dominant in the
upconversion excitation process as the upconversion excitation
mechanism of the Nd3+ excited-state levels is accomplished through a
stepwise multiphonon process. An efficient excitation energy transfer
(ET) has been observed between Nd3+ as a donor and Er3+ as the
acceptor. As a result, respective emission spectra had been observed.