Influence of Ho2O3 on Optimizing Nanostructured Ln2Te6O15 Anti‐Glass Phases to Attain Transparent TeO2‐Based Glass‐Ceramics for Mid‐IR Photonic Applications

The transparent TeO2‐based glass‐ceramics (GCs) have yet to achieve the breakthrough in photonic technologies, because of poor understanding in optimizing the growth of nanostructured crystalline phases. In the present investigation, the size effect of phase‐separation‐induced, nanostructured Ln2Te6O15‐based (Ln: Gd, Ho) “anti‐glass” phase in Ho2O3‐modified TeO2‐based TTLG (in mol%, 80TeO210TiO25La2O35Gd2O3) glass has considered to achieve transparent GCs. Raman study of TTLG glass reveals the presence of TeO3, TeO3 + 1, and TeO4 units with average TeO coordination number as 3.49. The formation of nanostructured Ln2Te6O15 phases in GCs is confirmed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. Furthermore, TEM analysis confirms that an increase of Ho2O3 concentration has reduced the size of phase‐separated domains in nanoscale with superstructure formation to attain transparent GCs. The superiority of this obtained transparent GCs as photonic material for near‐IR (NIR) to mid‐IR (MIR) range has been established by the realization of enhanced luminescence intensities and bandwidth at ≈2900 nm (Ho3+: 5I6 → 5I7) and ≈2050 nm (Ho3+: 5I7 → 5I8). This study offers an opportunity to fabricate the various accessible lanthanide ions‐doped and/or co‐doped TTLG glass with control over nanostructure, to design a series of GCs which are transparent from visible to MIR range

Cooling rate effects on the structure of 45S5 bioglass: Insights from experiments and simulations

Due to its ability to bond with living tissues upon dissolution, 45S5 bioglass and related compositions materials are extensively used for the replacement, regeneration, and repair of hard tissues in the human body. However, the details of its atomic structure remain debated. This is partially due to the non-equilibrium nature of glasses, as their non-crystalline structure is highly dependent on their thermal history, namely, the cooling rate used during quenching. Herein, combining molecular dynamics (MD) simulations with cooling rates ranging over several orders of magnitude and experimental studies using nuclear magnetic resonance (NMR), we investigate the structure of the nominal 45S5 bioglass composition. These results suggest that the MD simulation results when extrapolated to experimental cooling rates can provide a reasonable estimate of the structure of 45S5 bioglass. Finally, based on these results, we suggest the propensity of the phosphate group to form isolated orthophosphate species. Overall, these results reconcile the simulation and experimental results on the structure of 45S5 bioglass, and particularly on the speciation of the phosphate group, which may be key in controlling the bioactivity of 45S5 bioglass

Electrical and mechanical properties of Na2.8Ca0.1Al2Ga0.5P2.7O12 glass based electrolyte materials: Influence of Ag+ ion-exchange

Sodium super ionic conductor (NASICON) based glass is emerging as solid electrolyte material for Na-ion batteries. In the present study, we report the influence of Ag+ -> Na+ ion-exchange process on the electrical, optical, structural and mechanical properties of NASICON type glass with a chemical formula of Na2.8Ca0.3Al2Ga0.5P2.7O12 (NCAGP). Ag+ ion exchange process was carried out by dipping NCAGP glass in AgNO3 molten salt at 300 degrees C for 15 min (IE15min) and 30 min (IE30min). The diffusion depth of Ag+ ions was measured to be about similar to 7 mu rn and similar to 25 mu m for IE15min and IE30min samples, respectively. The dc conductivity values were obtained from base (NCAGP), IE15min and IE30min bulk glass samples through the complex impedance plots at a temperature range of 75 degrees C-200 degrees C. With the increase in ion-exchange time, the dc conductivity slightly diminished on account of marginally increase in activation energy (Ea) values. Optical absorption spectra for 30 min ion-exchanged glass revealed the localized surface plasmon resonance (LSPR) band, confirming the reduction of Ag+ ion to Ag-0 metal with an increase in ion-exchange time from 15 min to 30 min. Presence of Raman vibrational peak at 233 cm(-1) has also confirmed the formation of Ag-O bonds. The mechanical hardness values obtained through Vickers indentation method reveal enhanced hardness and crack resistance of bulk glasses with the ion-exchange treatment by causing compressive stress on the surface of NCAGP glass. The threshold load for the crack generation is increased from 0.5 kgf (4.9 N) to 2 kgf (19.6 N) after the ion-exchange treatment. Overall, improved mechanical and good electrical properties reveal the applicability of IE15min NCAGP glass as an electrolyte material for Na-ion batteries

Bandwidth enhancement of MIR emission in Yb3+/Er3+/Dy3+ triply doped fluoro-tellurite glass

Enhanced bandwidth of MIR emission from Yb3+/Er3+/Dy3+ triply doped low phonon oxide glass system has been reported in this work. With considerable gain cross-section, the MIR emission bandwidth can be stretched from similar to 2600 to 3100 nm (similar to 500 nm) which is practically not possible to obtain from Er3+ or Dy3+ ions singly doped systems. Co-doping of Dy3+ ions not only quenches the unfavourable visible up-converted emissions from Er3+ ions but also mitigates the prominent similar to 1.5 mu m emission. A broad MIR emission on superimposition of Er3+ similar to 2.76 mu m and Dy3+ similar to 2.95 mu m emissions was obtained owing to the efficient energy transfer (ET) Yb3+ -> Er3+ -> Dy3+ upon similar to 980 nm excitation. The present glasses can be fiberized to develop compact and tunable MIR solid state fiber laser sources

Insights into Er3+ ↔Yb3+ energy transfer dynamics upon infrared ~1550 nm excitation in a low phonon fluoro-tellurite glass system

Highly upconverting, monolithic transparent inorganic glass co-doped with Er3+/Yb3+ ions have been explored in view of their easy integration with Si-PV cell. A ~4 fold enhancement in the photo-current of mc-Si-PV cell has been observed using a Er3+/Yb3+ co-doped sample compared to Er3+ ions singly doped glass. The role of Yb3+ ions on the enhancement of photo-current has been discussed in light of the Er3+↔Yb3+ energy transfer mechanism involved from IR to NIR and VIS upconversion process upon IR ~1550 nm excitation. The influence of excitation pump power and donor Er3+ ion concentration on the energy transfer upconversion (ETU) as well as excited state absorption (ESA) energy transfer mechanisms and its effect on the upconversion emission properties have been described in detail. The prominence of ETU or ESA process were elaborated considering the decay dynamics of NIR upconversion emission upon ~1550 nm excitation

Bandwidth enhancement of MIR emission in Yb3+/Er3+/Dy3+ triply doped fluoro-tellurite glass

Enhanced bandwidth of MIR emission from Yb3+/Er3+/Dy3+ triply doped low phonon oxide glass system has been reported in this work. With considerable gain cross-section, the MIR emission bandwidth can be stretched from ~2600 to 3100 nm (~500 nm) which is practically not possible to obtain from Er3+ or Dy3+ ions singly doped systems. Co-doping of Dy3+ ions not only quenches the unfavourable visible up-converted emissions from Er3+ ions but also mitigates the prominent ~1.5 µm emission. A broad MIR emission on superimposition of Er3+ ~2.76 µm and Dy3+ ~2.95 µm emissions was obtained owing to the efficient energy transfer (ET) Yb3+  →  Er3+  →  Dy3+ upon ~980 nm excitation. The present glasses can be fiberized to develop compact and tunable MIR solid state fiber laser sources

Structure and Conductivity Correlation in NASICON Based Na3Al2P3O12 Glass: Effect of Na2SO4

Identifying the factors influencing the movement of sodium cations (Na+) in glasses accelerates the possible options of glass-based solid electrolyte materials for their applications as a promising electrolyte material in sodium-ion batteries. Nevertheless, due to the poor correlation between the structure and conductivity in glass materials, identifying the factors governing the conductivity still exists as a challenging task. Herein, we have investigated the DC-conductivity variations by correlating the structure and conductivity in sodium superionic conductor (NASICON) based Na3Al2P3O12 (NAP) glass (mol%: 37.5 P2O5-25.0 Al2O3-37.5 Na2O) due to the successive substitution of Na2SO4 for Al2O3. Structural variations have been identified using the Raman and magic-angle spinning nuclear magnetic resonance (MAS-NMR) (for P-31, Na-23, and Al-27 nuclei) and conductivity measurements have been done using the impedance spectroscopy. From the ac-conductivity spectra, the correlations between mean square displacement (MSD) and dc-conductivity and between the Na+ concentration and dc-conductivity have also been evaluated. Raman spectra reveal that the increase in the Na2SO4 concentration increases the number of isolated SO42- sulfate groups that are charge compensated by the Na+ cations in the NAP glass. MAS-NMR spectra reveal that the increase in Na2SO4 concentration increases the concentration of non-bridging oxygens and further neither S-O-P nor S-O-Al bonds are formed. Impedance spectroscopy reveals that, at 373 K, the DC conductivity of the NAP glass increases with increasing the Na2SO4 up to 7.5 mol% and then decreases with the further increase. In the present study, we have shown that the mobility of sodium cations played a significant role in enhancing the ionic-conductivity. Further, we have shown that inter-ionic Coulombic interactions and the structural modification with the formation of SO42- units significantly influence the critical hopping length of the sodium cations and consequently the mobility and the ionic conductivity. The present study clearly indicates that, based on the compositions, glass materials can also be treated as strong-electrolyte materials

Insights into Er3+ <-> Yb3+ energy transfer dynamics upon infrared similar to 1550 nm excitation in a low phonon fluoro-tellurite glass system

Highly upconverting, monolithic transparent inorganic glass co-doped with Er3+/Yb3+ ions have been explored in view of their easy integration with Si-PV cell. A 4 fold enhancement in the photo-current of mc-Si-PV cell has been observed using a Er3+/Yb3+ co-doped sample compared to Er3+ ions singly doped glass. The role of Yb3+ ions on the enhancement of photo-current has been discussed in light of the Er3+ Yb3+ energy transfer mechanism involved from IR to NIR and VIS upconversion process upon IR similar to 1550 nm excitation. The influence of excitation pump power and donor Er3+ ion concentration on the energy transfer upconversion (ETU) as well as excited state absorption (ESA) energy transfer mechanisms and its effect on the upconversion emission properties have been described in detail. The prominence of ETU or ESA process were elaborated considering the decay dynamics of NIR upconversion emission upon similar to 1550 nm excitation. (C) 2017 Elsevier B.V. All rights reserved