الفهرس 
Glass definition and kindsOnly 14 pages are availabe for public view
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Abstract
A melt quenching technique was used to successfully manufacture a series of
tellurite glass samples with the formula 80TeO2 - (20-X) WO3 - XNb2O5, where X
= 0, 1, 3, 5, 7.5, and 10 mol %. These samples were prepared using high-purity
chemicals. All of the prepared samples were amorphous in nature, pale yellow in
color, homogenous, transparent, clear, and free of imperfections and impurities.
Furthermore, no distinct peak was found in the XRD analysis.
Density ρ was measured using toluene as an immersion liquid, and it was
found that as the percentage of Nb2O5 increased, the density of the sample decreased.
The rationale behind this is that Nb2O5 has a lower density than both TeO2 and WO3.
In contrast, the molar volume values demonstrated an increase in the same structure
due to atomic rearrangement brought about by the substitution of Nb2O5 for WO3,
which increased the ring size and opened up the network.
The glass transition temperature (Tg), the crystallization temperature (Tc), and
the onset of crystallization temperature (Tx) were measured using the DSC technique
over a temperature range from room temperature to 600°C at a heating rate of
10°C/min. Powdered quantities of samples with masses ranging from 5 mg to 10 mg
were used for this measurement. The results of the quantitative analysis indicated
that when the percentage of Nb2O5 increased, the values of (Tg), (Tx), and (Tc) also
increased. As the percentage of Nb2O5 increased, the thermal stability value of the
glass (S) decreased, indicating that it can be heated above (Tg) without
crystallization.
In order to examine the internal structure of glass samples, an FTIR
spectrum covering the range 4000–400 cm-1 was employed. Tellurite glass has an αTeO2 crystalline pattern, which is made up of (TeO4) groups in the form of Te-eq Oax
-Te dimers. When modifier materials like Nb2O5 are added, the three-dimensional
network is altered, resulting in the creation of (NBO) types. As the (NbO6) units
penetrate the glass mesh network and the Te-O-Te bonds in these samples are
broken, they gradually transform into TeO3+1 and TeO3. The findings also
demonstrated that the infrared absorption band intensity through the samples
decreased with increasing Nb2O5 ion concentration. Also, no absorption band of
water or (OH) groups from outside air or any raw material appeared in the infrared
spectrum, which means that the prepared glass samples can be used in optical fiber
amplifiers.
Using the USN 60 system and the Digital Lecroy Oscilloscope, the pulse echo
method was applied at room temperature to study the mechanical properties.
Ultrasonic velocities measurement was used to ascertain the elastic properties of the
glass samples by comparing their prior velocities. The speed of the longitudinal and
transverse ultrasonic waves increases due to the increase in molar volume, which
increases the ultrasound waves’ propagation through the samples. The elastic moduli
(longitudinal elastic modulus L, volumetric elastic modulus K, shear elastic modulus
G, and Young’s modulus E), as well as the values of Poisson’s ratio and
Microhardness (H), were determined based on the velocity of ultrasonic waves.
The hardness of the samples increases as the concentration of Nb2O5
increases, as indicated by the values of elasticity coefficients rising with the contents
of Nb2O5 in the samples. This is caused by the production of BO as a result of TeO3
and NbO3 formation. The strength of the glass samples’ internal structure is further
supported by the results, which also indicated a rise in Debye temperature.
The values of elasticity coefficients were theoretically determined as an
extension of the mechanical property study, using the Bond compression model as
well as the Makishima and Mackenzie model. The findings showed that as Nb2O5
concentration increases, the nb decreases, and as ̅F increases the value of bond
compression bulk modulus slightly decreases. This indicates a discrepancy between
the results of theoretical calculations in the Bond model compression and the results
of actual measurements.
The Makishima and Mackenzie model’s results showed that when Nb2O5
concentration rises, the dissociation energy per unit volume rises as well. This is
because Nb2O5 replaces WO3, and tungsten oxide has dissociation energy of 67.8
J.cm-3
, while niobium oxide has dissociation energy equals 85.4 J.cm-3
. As a result,
the elasticity coefficients Em, Km, Lm and Gm increased. This shows that theoretical
computations based on the Makishima and Mackenzie model and actual
measurements agree.
These findings suggest that the thermal and mechanical characteristics of
niobium tungsten tellurite glass have been improved for use in a variety of
applications, particularly as a host material.