Tbp Units Research Articles

Structures and Ligand Field Parameters of Sm<sup>3+</sup> Doped Tellurite Glass: Gold Nanoparticles Mediation

Controllable modifications of overall properties of rare-earth doped glasses via gold nanoparticles (Au NPs) mediation prompted gamut research interests. Such glass systems are interesting due to their technological prospects and well as fundamental understanding of surface plasmon resonance effects at metal glass interface responsible for diverse emerging attributes. This motivate us to determine the effects of varying concentration of Au NPs on the structure and ligand field parameters of samarium (Sm3+) doped zinc tellurite glass. Glass samples with composition (79-x)TeO2-20ZnO-1Sm2O3-xAuCl3, where 0 ≤ x ≤ 0.10 mol% are prepared using melt quenching method. X-ray diffraction pattern of all glasses confirmed their amorphous nature. Transmission electron microscopic images verified the existence of Au NPs in a glass matrix matrix with an average size of 10.52 nm. Two surface plasmons resonance band of gold are probed at 652 and 715 nm. Using the UV-Vis absorption spectral data, quantities such as nephelauxetic ratio, bonding parameter and Racah parameters are evaluated. Both bonding parameter and nephelauxetic ratio revealed a reduction with increasing concentration of Au NPs, where decrease in the ionic bonding between Sm3+ and surrounding ligand have clearly indicated an enhancement in the covalency. The values of Racah parameters are decreased as the concentration of Au NPs are increased. The observed reduction in the nephelauxetic function is attributed to the weakening of the localized d-electrons aroused from overlapping d-orbital and ligand orbital. Furthermore, the Raman spectra displayed the structural modification in terms of TeO4 trigonal bipyramidal (tbp) unit, where many TeO4 tbp units are converted into their TeO3 trigonal pyramid (tp) counterparts. Raman bands are found to be located around 102-105 cm-1, 420-424 cm-1, 657-661 cm-1 and 729-736 cm-1. Results are analyzed and compared. Present glass composition is asserted to be useful for the development of photonic devices.

Effect of TeO2 Addition on the Mobility of Silver Ions in Ag2O-B2O3-P2O5-TeO2 Glasses

The effect of adding TeO2 into (100-x)[0.5Ag2O−0.1B2O3−0.4P2O5]−xTeO2 glasses, with 0−80 mol% TeO2, on the structural changes and electrical properties has been investigated. The structure was studied by Raman spectroscopy and electrical properties have been studied over a wide temperature and frequency range by impedance spectroscopy. The addition of the third glass former, TeO2, to the glass network causes the structural transformation from TeO3 (tp) to TeO4 (tbp) which contributes to the changes in conductivity. The glasses with low TeO2 content show only a slow decrease in dc conductivity with addition of TeO2 due to the increase of the number of non-bridging oxygens, which increases the mobility of Ag+ ions. The steep decrease in conductivity for glasses containing more than 40 mol% TeO2 is a result of decrease of the Ag2O content and stronger cross-linkage in glass network through the formation of more Te-eqOax-Te bonds in TeO4 tbp units. The glasses obey scaling of the ac conductivity with respect to temperature indicating that the dynamic process is independent of temperature. However, the scaling of the spectra for different glasses revealed deviations from the Summerfield scaling due to the local structural disorder caused by structural transition in tellurite glass network.

Electrical mobility of silver ion in Ag2O-B2O3-P2O5-TeO2 glasses.

The effect of adding TeO(2) into (100 - x)[0.5Ag(2)O - 0.1B(2)O(3) - 0.4P(2)O(5)] - xTeO(2), with 0-80 mol % TeO(2) glass, on the structural changes and electrical properties has been investigated. DSC and thermodilatomery were used to study their thermal behavior, structure was studied by Raman spectroscopy, and electrical properties have been studied by impedance spectroscopy over a wide temperature and frequency range. The introduction of TeO(2) as a third glass former to the glass network causes the structural transformation from TeO(3) (tp) to TeO(4) (tbp) which contributes to the changes in conductivity. The glasses with low TeO(2) content show only a slow decrease in dc conductivity with addition of TeO(2) due to the increase of the number of nonbridging oxygens, which increases the mobility of Ag(+) ions. The steep decrease in conductivity for glasses containing more than 40 mol % TeO(2) is a result of decrease of the Ag(2)O content and stronger cross-linkage in glass network through the formation of more Te-(eq)O(ax)-Te bonds in TeO(4) tbp units. The glasses obey ac conductivity scaling with respect to temperature, implying that the dynamic process is not temperature dependent. On the other hand, the scaling of the spectra for different glass compositions showed the deviations from the Summerfield scaling because of the local structural disorder which occurs as a result of the structural modifications in the tellurite glass network.

Evolution of local structure in Ag 2O–TeO 2 glasses with addition of Ag 2O analyzed by pulsed neutron diffraction and Raman spectroscopy

The local structure of Ag 2O–TeO 2 glasses was studied by time-of-flight pulsed neutron diffraction (TOF-PND) and Raman spectroscopy. The results of Raman spectroscopy indicated that TeO 4 trigonal bipyramidal units (tbp) were converted to TeO 3 trigonal pyramidal units (tp) by addition of Ag 2O to TeO 2. Furthermore in PND, the structural parameters for each atomic pair were optimized in the Q-space, and the distances of the near neighbor Te–O correlations forming tbp units and tp units in the network were estimated with some accuracy.

Raman spectroscopic study of Nd-doped 10Na 2O–90TeO 2 glasses

Over the Nd 2O 3 concentration region from 0.1 to 2.5 mol%, our Raman spectroscopic study showed that adding Nd to a base 10Na 2O–90TeO 2 tellurite glass converts TeO 4 trigonal bipyramid (tbp) units to TeO 3 trigonal pyramid (tp) units and possibly some terminal TeO 3+1 polyhedra. The Nd effect on the speciation of tellurite structural groups is similar to that of other monovalent (such as alkalis), divalent (such as Zn), and trivalent (such as La) metal cations. The previously observed Nd–O local structural transition was also found in the current study. Namely, a transition near 1 mol% Nd 2O 3 was observed in the correlations, both band position and intensity, between two Raman stretching vibration bands near 600 and 730 cm −1 . The former represents the stretching vibration mode of TeO 4 tbp units and the latter represents the stretching vibration mode of TeO 3 tp units. A Raman band, near 465 cm −1 , represents a bending vibration mode of Te–O–Te (or O–Te–O) linkages. Our study showed a significant decrease in the E-band intensity of the glass with 2.5 mol% Nd 2O 3. It follows that a considerable structure disruption of the tellurite network takes place when the Nd cation is close to its solubility limit.

High-temperature structure of K 2O–TeO 2 glasses

The structural change of K 2O–TeO 2 glasses ( xK 2O:TeO 4, x:5, 10, 15, 20, 25 and 30 mol%) from room temperature to a temperature higher than the melting point ( T m) was studied by the use of Raman spectroscopy, XRD (X-ray diffraction), X-ray RDF (radial distribution function) and XAFS (X-ray absorption fine structure) spectroscopy. The Raman results indicated that TeO 4 trigonal bipyramid (tbp) units convert to TeO 3 trigonal pyramid (tp) units with increasing temperature and by the addition of K 2O to the K 2O–TeO 2 glasses. We found that a 10K 2O · 90TeO 2 (mol%) glass mainly consists of TeO 4 tbp unit, while 20K 2O · 80TeO 2 (mol%) and 30K 2O · 70TeO 2 (mol%) glasses are composed of the mixture of TeO 4 tbp and TeO 3 tp units. The high-temperature XRD and X-ray RDF results are in agreement with the results of high-temperature Raman spectroscopy. Furthermore, the XAFS spectroscopy shows that potassium ions have a similar local structure in all of the K 2O–TeO 2 glasses studied.