Materials Science Forum Vol. 846

Abstract: Borotellurite glasses were generally applied in rare earth optical materials due to their excellent physical properties. Samarium doped borotellurite glasses have been identified as one of the potential candidate for optical applications. Therefore, the aim of this study is to identify the physical properties of Sm³⁺ doped borotellurite glasses by mean of their density, molar volume, microhardness and X-ray diffraction. In this study, the Sm³⁺ doped borotellurite glasses of the system (70-x)TeO₂-20B₂O₃-10ZnO-xSm₂O₃ as the samarium trioxide varies from (x = 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) have been prepared by melt-quenching method. The amorphous nature of the prepared glass samples have been confirmed through XRD spectral analysis. The values of density are found to vary from 4.541g/cm³ to 4.837g/cm³ as well as the values of molar volume as it varies from 29.118cm³/mol to 28.314cm³/mol with the increase of Sm³⁺ content. The physical properties corresponding to compositional changes have been analysed and the result are reported and presented.

Abstract: The luminescence properties of rare earth in glass are interesting to study and being one of attractive properties in development of laser. A series of Eu^3+/Dy³⁺ co-doped magnesium tellurite borophosphate glass has been prepared with nominal composition 50B₂O₃-15P₂O₅-25MgO-10TeO₂. The amorphous phases of the sample were characterized using X-ray diffraction pattern and the presence of a broad hunch shows that the sample in an amorphous state. For Eu^3+/Dy³⁺ co-doped borophosphate glass sample of consist five peaks where Eu³⁺ emission were located at 611 nm, 662 nm and 699 nm due to the transition of ⁵D₀-⁷F_J ( J = 2, 3, 4) while the Dy³⁺ emission is due to transition ⁴F_9/2-⁵H_J/2 (J = 15 and 13). Furthermore, glass sample showed exponential decay curve and lifetime for glass sample is determined.

Abstract: Nickel nanoparticles are incorporated in Sm³⁺ doped zinc phosphate glass having a composition of 40ZnO-(58-x)P₂O₅-1Sm₂O₃-xNiO, with x = 0.0 and 2.0 mol% prepared by melt quenching technique. Sample characterizations are made by means of X-ray diffraction, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). X-ray diffraction shows that the glass is in amorphous state. The transmission electron microscopic (TEM) image reveals the existence of Nickel nanoparticles having a particles size in the range of 5.5 – 21.8 nm. The magnetization M(H) curve reveals that the glass displays an anomalous hysteresis behavior at room temperature. It is observed that the initial curve of magnetization lies positively as a function of magnetic field under 1000 H (O.e).

Abstract: The demand for tunable surface plasmon (SP) of embedded metal nanoparticles (NPs) in rare earth doped inorganic lasing glasses is ever-growing. Following melt quenching method Er³⁺ doped zinc-boro-tellurite glasses containing silver (Ag) NPs are prepared. Glasses are heat treated (thermally annealed) at varying temperatures and time duration to alter the NPs morphology which generates SP. The annealing assisted SP resonance mediated modification in spectral features is discerned. Samples heat treatment at 410 °C for 6 hrs duration ensures the reduction of Ag+ ions to Ag^o NPs. Thermally annealed glasses are characterized via XRD, UV–Vis-IR absorption, photoluminescence spectroscopy, and TEM imaging. XRD spectra confirm the amorphous nature of the glass and TEM image reveals the existence of homogeneously distributed spherically shaped silver NPs of average diameter ~4.5 nm. NPs are found to grow with the increase of both annealing time and temperature. The UV–Vis spectra exhibit seven absorption bands corresponding to 4f–4f transitions of Er³⁺ ions in the wavelength range of 500-650 nm. The localized SPR band is evidenced at 550 and 580 nm. Heat treatment causes a red shift of the plasmon peaks ascribed to the alteration in glass refractive index. Furthermore, the glass sample annealed for 6 hrs displays maximum enhancement in the emission intensity corresponding to the peaks centered at 536 (²H_11/2→⁴I_15/2), 550 (⁴S_3/2→⁴I_15/2) and 632 nm (⁴F_9/2→⁴I_15/2). This enhancement is primarily attributed to the local field effect of the silver NPs. Admirable features of the results suggest that our systematic method for heat treatment in tuning NPs size assisted SPR may contribute towards the development of functional glass.

Abstract: Pure SnO₂ and Pt doped SnO₂ (0≤Pt≤10wt.%) ceramics have been successfully fabricated in the form of pellet by sintering at 1000 °C for 3 h. The resistance of the samples in air and in reducing gases (200 ppm H₂ and 200 ppm CO) was determined by measuring current – voltage (I-V) characteristics via two-probe method between 150 to 450 °C. All samples show a decrease in resistance with an increase in temperature both in air and in gases. However, the values of resistance in gases are lower compared when the same samples were in air, due to gas molecules reactions with surface oxygen species which affect potential barrier to decrease and causes resistance to reduce. The resistance of the doped samples also increased by 279 - 1226% with an increase in Pt doping in SnO₂, due to Pt surface states density.

Abstract: Spectral features modification of rare earth (RE) doped tellurite glasses via controlled manipulation of metallic nanoparticles (NPs) is the current challenge in achieving enhanced lasing action. Triggering the localized surface plasmon resonance (SPR) of NPs in the glass generates tremendous applied interests especially in solid state lasers and nanophotonics. Despite several promising features of RE doped zinc-boro-tellurite glass, the low absorption and emission cross-section of RE ions prohibit them from fabricating efficient lasers. This drawback needed to overcome and significant enhancement of spectral features is required. Co-doping by rare earths and/or embedding metallic NPs (acts as sensitizer) are demonstrated to be the alternative route to surmount such shortcomings. Series of glass samples with composition 74TeO₂–15B₂O₃–10ZnO– 1Sm₂O₃ – (x)Ag, where 0 ≤ x ≤ 0.1 mol% (in excess) are prepared using melt quenching method and the impacts of silver (Ag) NPs concentrations in altering their photoluminescence properties are inspected. The XRD spectra confirmed the amorphous nature of prepared glasses and the presence of Ag NPs are evidenced in EDX spectra. TEM micrographs revealed the distribution of Ag NPs with average size 7.2 nm. Absorption spectra revealed eight bands which most intense between ⁶F_11/2 and ⁶F1_/2. Photoluminescence spectra exhibited three prominent peaks corresponding to the transition from the excited state ⁴G_5/2 to ⁶H_5/2, ⁶H_7/2, and ⁶H_9/2 states, respectively. Our observation may be useful for the development of tellurite glass based nanophotonic devices.

Abstract: A series of (x) paper ash- (80-x) cullet – 20 Kaolin clay where 10 ≤x≤30 weight % has successfully been prepared using solid state reaction method. The ceramic density and hardness has been determined using Archimedes and Vickers hardness method respectively. The dielectric constant and dielectric loss has been determined using impedance analyzer. The obtained density is descending from 2.18 gcm^-3 to 1.90 gcm^-3 and hardness is increased up to 871.8 Mpa. The decrement of density and hardness as the cullet content increases is due to the non uniform vitreous areas formed in between ceramic particle. The variation of the dielectric constant and dielectric loss tangent are found to decrease with increasing of frequency which suggest the dipolar polarizability properties. It is found that the maximum value of dielectric constant is 3000 and minimum dielectric loss tangent is 0.166.

Abstract: A series of tellurite glass containing samarium ion and silver nanoparticles with a composition of (89.6-x)TeO₂-10MgO-(x)Sm₂O₃-0.4AgCl with 0.2 ≤ x ≤ 1.0mol% have been synthesized by a conventional melt quenching technique. The X-ray diffraction pattern verified the amorphous nature of glasses. A systematic study on the relationship between Sm₂O₃ concentration and the physical properties of the glass has been made. The effect on the progressive replacement of TeO₂ by Sm₂O₃ on density, molar volume, refractive index and electronic polarisability has been investigated. The results show that density and ionic packing density are in the range of 4.91-5.04 g cm^-3 and 0.444 – 0.455, respectively, increases as the amount of Sm₂O₃ is increased up to 0.8 mol% and decrease afterward. However, the molar volume which is in between, 29.59-30.26 m³ mol^-1 decreasing as the amount of Sm₂O₃ is increased up to 0.8 mol% and increase thereafter. Meanwhile the refractive index which is deduced from optical energy band gap is found to possess a value in the range of 2.37 to 2.45 and electronic polarisability is in the range of 7.14-7.51ų. All the results will be discussed with respect to the glass composition.

Abstract: The vulnerability of varistor ceramics to electrical degradation during operation not only affects their nonlinear properties but also leads to shortening of device’s lifetime by increasing the risk of failures including melting, fire or even explosions. In this study, ZnO-Pr₆O₁₁-Cr₂O₃ varistor ceramics were prepared through modified citrate gel method and solid state-sintering at 1250 °C for 1 hour. The stability of their nonlinear properties under prolonged application of DC electrical field in high temperature ambient was investigated. Degradation process was accelerated by applying direct current (DC) electrical field of 15 % below the breakdown field point of ceramics for 54 hours consecutively at temperature of 30 to 125 °C. The findings indicate that ZnO-Pr₆O₁₁-Cr₂O₃ ceramics exhibited its susceptibility to electrical degradation after prolonged electrical and thermal stresses application. Its nonlinear coefficient has reduced by 4.4 % reduction, the breakdown field has reduced by 9.9 % and the leakage current density increased by 13.7 % in comparison to its initial value. Degradation process in varistor ceramics of ZnO-Pr₆O₁₁-Cr₂O₃ was a direct response to collapsed Double Schottky Barrier at ZnO grain boundary.

Abstract: Optimizing the rare earth doping in inorganic binary glasses for tuneable structural and optical properties is ever-demanding for lasing glass. A series of Er³⁺ and Nd³⁺ doped lithium niobate tellurite glasses with compositions of (70-x-y)TeO₂–15Li₂CO₃–15Nb₂O₅–(x)Er₂O₃–(y)Nd₂O_3, where x = 0.0, 1.0 mol % and 0 ≤ y ≤ 1.0 mol% are synthesized using melt-quench technique. Influence of Nd³⁺ ion concentrations on physical and optical behaviour is examined. X–Ray diffraction pattern confirm the amorphous nature of glasses. The strong dependence of spectral properties on rare-earth dopant indicates the alteration in structures and bonding of glass network. The structural properties of the glass represented by the FTIR spectrum indicate that as Nd₂O₃ content increases, the sharp infrared absorption peaks are shifted from 474.7 cm^-1 to 499.4 cm^-1. These peaks are due to Nb-O, Te-O-Te and O-Te-O bond linkage bending vibrations. For TeO₄ trigonal bipyramid, the peak occurred at 676.5 cm^-1 whereas for TeO₃ trigonal pyramid, two infrared band peaks are found at 787.5 cm^-1 and 887.6cm^-1, respectively. The absorption peaks around 1382.7 cm^-1 is due to the Te – O – Nb stretching vibration while peaks at 1635.5cm^-1 and 3411.7 cm^-1 are due to the stretching vibrations of the hydroxyl group participating in the strong metal bonding as well as in the hydrogen bonding, respectively.