Niobium Tellurite Glasses Research Articles

Probing the elasticity and radiation protection potential of neodymium(III) doped zinc and niobium tellurite glasses: An integrated simulated and applied physics perspective

The present work scrutinizes the radiation protection features and mechanical characteristics of neodymium zinc-tellurite of composition (TeO2)75-(ZnO)10 – (Nb2O5)15−x - (Nd2O3)x: x = 0–9 mol%. An MCNP Monte Carlo simulation code and Phy-X software were performed to evaluate the radiation shielding parameters (e.g., linear attenuation coefficient (μ), mass attenuation coefficient (μm), half value layer (H1/2), etc. of the investigated TZNNdx glasses. Results revealed that the increasing of Nd2O3 concentration in TZNNd-glasses from 1 to 9 mol% had a positive effect on their elastic parameters: Young's modulus increased from 52.949 to 55.44 GPa, bulk modulus changed from 31.189 to 34.411 GPa, and the PR varied from 0.217 to 0.228 for TZNNd1 to TZNNd5. Compared to prior research on similar compositions, our findings indicate a more pronounced enhancement in both mechanical and Radiation shielding properties, suggesting an optimized composition strategy. The linear attenuation coefficient (μ) increased in the order TZNNd0 < TZNNd3 < TZNNd5 < TZNNd7 < TZNNd9. The half-value layer varies inversely with the linear attenuation coefficient and varies from 0.004 to 3.600 cm for TZNNd0, 0.003–3.453 cm for TZNNd3, 0.003–3.346 cm for TZNNd5, 0.003–3.253 cm for TZNNd7, and 0.003–3.159 cm for TZNNd9. Throughout the considered energy spectrum, the range of Zeff for the glasses varied from 44.98 to 30.51, 46.31 – 31.51, 47.13 – 32.18, 47.89 – 32.85, and 48.61 – 33.53 for TZNNd0, TZNNd3, TZNNd5, TZNNd7, and TZNNd9, respectively. Also, the values of fast neutron removal cross-section ΣR were calculated and showed a steady increase as the partial densities of Nd and oxygen of the TZNNd-glass systems increased. The FNRCS (∑R) of the TZNNd glass samples have FNRCS values of 0.093, 0.106, 0.107, 0.108, and 0.109 cm−1 for TZNNd0, TZNNd3, TZNNd5, TZNNd7, and TZNNd9, respectively Generally, one can conclude that the additive of Nd2O3 to Nb2O5-TeO2-ZnO glasses enhances their mechanical properties and increases their ability to absorb neutrons and photons to apply in nuclear medicine applications.

Structure of bismuth tellurite and bismuth niobium tellurite glasses and Bi2Te4O11 anti-glass by high energy X-ray diffraction.

Glass and anti-glass samples of bismuth tellurite (xBi2O3–(100 − x)TeO2) and bismuth niobium tellurite (xBi2O3–xNb2O5–(100 − 2x)TeO2) systems were prepared by melt-quenching. The bismuth tellurite system forms glasses at low Bi2O3 concentration of 3 to 7 mol%. At 20 mol% Bi2O3, the glass forming ability of the Bi2O3–TeO2 system decreases drastically and the anti-glass phase of monoclinic Bi2Te4O11 is produced. Structures of glass and the anti-glass Bi2Te4O11 samples were studied by high-energy X-ray diffraction, reverse Monte Carlo simulations and Rietveld Fullprof refinement. All glasses have short short-range disorder due to the existence of at least three types of Te–O bonds of lengths: 1.90, 2.25 and 2.59 Å, besides a variety of Bi–O and Nb–O bond-lengths. The medium-range order in glasses is also disturbed due to the distribution of Te–Te pair distances. The average Te–O co-ordination (NTe–O) in the glass network decreases with an increase in Bi2O3 and Nb2O5 mol% and is in the range: 4.17 to 3.56. The anti-glass Bi2Te4O11 has a long-range order of cations but it has vibrational disorder and it exhibits sharp X-ray reflections but broad vibrational bands similar to that in glasses. Anti-glass Bi2Te4O11 has an NTe–O of 2.96 and is significantly lower than in glass samples.

Spatially resolved X-ray fluorescence, Raman and photoluminescence spectroscopy of Eu3+/Er3+ doped tellurite glasses and anti-glasses

Strontium tellurite, lead tellurite and bismuth niobium tellurite glasses containing 1 to 2 mol% of Eu3+ and Er3+ were prepared by melt-quenching and found to contain anti-glass inclusions (droplet phase) of size of several micrometers. Anti-glasses are disordered crystals that have long-range order of the cations such as Sr2+, Pb2+, Bi3+, Nb5+ and Te4+ but have a disordered arrangement of the anions (O2−), therefore these materials exhibit sharp peaks in the X-ray diffraction patterns due to the long range cationic order but the Raman spectra show broad bands due to the vibrational disorder. The glass matrix and anti-glass inclusions in the samples were characterized by synchrotron micro-X-ray Fluorescence (XRF), Raman and photoluminescence mapping studies. The XRF line analysis confirmed that the anti-glass and glass matrix phases have equal concentration of metal ions. The samples containing Eu3+ show intense red photoluminescence at an excitation wavelength of 375 nm, while Er3+ doped samples exhibit strong green emission by the up-conversion of infrared photons (980 nm). The spatially resolved XRF, Raman and photoluminescence spectroscopy found that the inclusions and the glass matrix have the same metal ion concentration, short-range order, TeO speciation and the light emission properties.

Acoustic relaxation of some lead niobium tellurite glasses

The longitudinal ultrasonic attenuation in xNb2O5−(1−x)TeO2, 0.1PbO −xNb2O5−(0.9 −x)TeO2 and 0.2PbO −xNb2O5− (0.8 −x)TeO2 tellurite glass systems was measured using the pulse echo technique at ultrasonic frequencies 2, 4, 6 and 8 MHz in the temperature range from 150 to 300 K. The absorption curves showed the presence of well-defined broad peaks at various temperatures depending upon the glass composition and operating frequency. The maximum peaks move to higher temperatures with the increase of operating frequency, indicating the presence of some kind of relaxation process. This process has been described as a thermally activated relaxation process, which happens when ultrasonic waves disturb the equilibrium of an atom vibrating in a double-well potential in the glass network structure. Results proved that the average activation energy of the process depends mainly on the modifier content. This dependence was analysed in terms of the loss of standard linear solid type, with low dispersion and a broad distribution of Arrhenius-type relaxation with temperature-independent relaxation strength. The experimental acoustic activation energy has been quantitatively analysed in terms of the number of loss centres (number of oxygen atoms that vibrate in the double-well potential).

Enhanced green upconversion by controlled ceramization of Er3+–Yb3+ co-doped sodium niobium tellurite glass–ceramics for low temperature sensors

Tellurite based glasses are well-known for their upconversion properties besides having a disadvantage of low mechanical strength dragging them away from practical applications. The present work deals with preparation of sodium niobium tellurite (SNT) glasses using melt quenching method, in which small quantities of boron and silicon in the form of oxides are added to improve their mechanical properties. Controlled heat treatment is performed to ceramize the prepared glasses based on the thermal data given by DTA. XRD and SEM profiles of the glass–ceramics which confirmed the formation of crystalline monoclinic Sodium Tellurium Niobium Oxide (Na1.4Nb3Te4.9O18) phase (JCPDS card No. 04–011-7556). Upconversion measurements in the visible region were made for the prepared Er3+–Yb3+ co-doped glasses and glass–ceramics with 980nm laser excitation varying the laser power and concentration of Er3+ ions. Results showed that the upconversion luminescence intensity was enhanced by ten times in SNT glass–ceramics compared to that in the SNT glasses. Decay curves give evidence of high performance of glass–ceramics compared to glasses due to ceramization and structural changes. Temperature dependent visible upconversion was performed to test the ability of efficient SNT glass–ceramic at low temperatures and variation of upconversion intensities was studied.

Effects of Nb 2 O 5 on thermal stability and optical properties of Er 3+ -doped tellurite glasses

Er3+-doped tellurite glasses with molar compositions of xNb2O5−(14.7−x)Na2O–10ZnO–5K2O–10GeO2– 60TeO2–0.3Er2O3 (x = 0,3,5,7 and 9) have been investigated for developing 1.5 μm fibre and planar amplifiers. The effects of Nb2O5 on the thermal stability and optical properties of Er3+-doped tellurite glasses have been discussed. It is noted that the incorporation of Nb2O5 (x = 5) increases the thermal stability of tellurite glasses significantly. Er3+-doped niobium tellurite glasses exhibit a large stimulated emission cross-section (7.2×10−21−10.7×10−21 cm2) and the gain bandwidth, FWHM×σepeak (274×10−28−480×10−28 cm3), which are significantly higher than that of silicate and phosphate glasses. In addition, the intensity of upconversion luminescence of the Er3+-doped niobium tellurite glasses decreases rapidly with increasing Nb2O5 content. As a result, Er3+-doped niobium tellurite glasses might be a potential candidate for developing laser or optical amplifier devices.

Structure of zinc and niobium tellurite glasses by neutron and x-ray diffraction**Some of these results have already been presented in thesis work: Yousef E 2003 Astudy of some physical properties of tellurite glass (Al-Azhar University, AssiutEgypt).

Neutron and x-ray diffraction experiments of high resolving power with neutrons from aspallation source and high-energy photons from a synchrotron have been performed oncompositional series of binary Zn, Nb and on mixed Zn/Nb tellurite glasses. The Te–O,Zn–O and Nb–O coordination numbers are determined by Gaussian fitting of thefirst-neighbour peaks in the neutron and x-ray data simultaneously. The transition ofTeO4 toTeO3 units with increasing fraction of a second component is indicated by decreasing total Te–Ocoordination numbers. This transition appears different for glasses with ZnO orNb2O5 additions. Details of the Te–O peaks suggest there are two species of Te–O bonds withlengths of and nm. The change of their fractions shows excellent agreement with the existence ofTeO4 trigonalbipyramids and TeO3 trigonal pyramids. All oxygen atoms from ZnO andNb2O5 areused for rupture of Te–O–Te bridges, which is accompanied with a change of nearly all participatingTeO4 toTeO3 groups. The tendency for a change decreases for glasses of higher second component content which is accompanied by the occurrenceof TeO4 groups with non-bridging oxygens. The Nb tellurite glasses show transition tonetwork-forming behaviour with the formation of Nb–O–Nb bridges. The fractions ofTeO3 unitsof ternary Zn/Nb tellurite glasses agree with an additivity behaviour of the modifying effects of ZnOand Nb2O5 additions.

Waveguide formation in niobium tellurite glasses by pico- and femtosecond laser pulses

We obtained a temporal and permanent refractive index change in niobium tellurite glasses by using ps- and fs-pulses, respectively. A He–Ne laser beam was guided by a line waveguide structure drawn by the fs-pulses, indicating positive refractive index change. It is suggested that the refractive index change by the ps-pulses is due to an increase in the absorption coefficient while that caused by the fs-pulses results from the rearrangement of the glass structure.

Time dependence and energy-transfer mechanisms in Tm 3+, Ho 3+ and Tm 3+–Ho 3+ co-doped alkali niobium tellurite glasses sensitized by Yb 3+

Glass samples with the composition (mol%) 80TeO 2–10Nb 2O 5–5K 2O–5Li 2O, stable against crystallization, were prepared containing Yb 3+, Tm 3+ and Ho 3+. The energy transfer and energy back transfer mechanisms in samples containing 5% Yb 3+–5% Tm 3+ and 5% Yb 3+–5% Tm 3+–0.5% Ho 3+ were estimated by measuring the absorption and fluorescence spectra together with the time dependence of the Yb 3+ 2 F 5/2 excited state. A good fit for the luminescence time evolution was obtained with the Yokota–Tanimoto's diffusion-limited model. The up-conversion fluorescence was also studied in 5% Yb–5% Tm, 5% Yb–0.5% Ho and 5% Yb–5% Tm–0.5% Ho tellurite glasses under laser excitation at 975 nm. Strong emission was observed from 1 G 4 and 3 F 2 Tm 3+ energy levels in all samples. The 5 S 2 Ho 3+ emission was observed only in Yb 3+Ho 3+ samples being completely quenched in Yb 3+/Tm 3+/Tm 3+ samples.

Raman scattering, differential scanning calorimetry and Nd 3+ spectroscopy in alkali niobium tellurite glasses

Alkali niobium tellurite glasses have been prepared and some of their properties measured by differential scanning calorimetry and Raman scattering. The vitreous domain was established in the pseudo ternary phases diagram for the system TeO 2–Nb 2O 5–(0.5K 2O–0.5Li 2O). Raman scattering shows that for samples in the TeO 2 rich part of the phase diagram the vitreous structure is composed essentially of (TeO 4) units connected by the vertices, as in the α-TeO 2 crystal. The addition of alkali and niobium oxides causes depolymerization to occur with structures composed essentially of (TeO 3) and (NbO 6) units. Samples with the composition (mol%) 80TeO 2–10Nb 2O 5–5K 2O–5Li 2O, stable against crystallization, were prepared containing up to 10% mol Nd 3+. The addition of this oxide increases the rigidity of the vitreous network shifting characteristic temperatures to higher temperatures. For the 10% Nd 3+ sample amorphous phase separation is assumed to exist from the observation of two glass transition temperatures. Spectroscopic properties such as Judd–Ofelt Ω λ intensity parameters, radiative emission probabilities, and induced emission cross sections were calculated. From these results and also from the emission quenching observed as a function of Nd 3+ concentration, we suggest that these glasses could be utilized in optical amplifying devices.