Zahra Ashur Said Mahraz

Thermal stability and Judd-Ofelt analysis of optical properties of Sm3+-doped sodium tellurite glasses

Series of glasses based on (70-x) TeO2 – 20Na2O – xSm2O3 (x=0, 0.3, 0.6, 1, 1.2, 1.5 mol%) have been prepared using melt-quenching technique. The nature of the glass has been confirmed using X-ray diffraction; it is found that the glass samples are amorphous in nature. The thermal stability of the glass has been determined by means of Differential Thermal Analysis (DTA). From the DTA curve, the glass transition temperature (Tg), crystallization temperature (Tc) and melting temperature (Tm) have been identified and thermal stability is also calculated. The absorption properties of these samples are obtained by using UV-Visible-NIR spectrometer, the recorded absorption spectra exhibit nine absorption transition bands peaks corresponding to the transitions from ground level 6H5/2→6P3/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2. The emission characteristic of this glass is characterized using Photoluminescence (PL) spectroscopy at excited wavelength 404 nm, the emission spectra consisted of four emission bands at 561.95 nm, 598.69 nm, 643.77 nm and 704.56 nm which were assigned as a transition 4G5/2→6H5/2, 6H7/2, 6H9/2 and 6H11/2 respectively. From f-f intensity model the experimental oscillator strengths, fexp and theoretical oscillator strength fcal were calculated. Using Judd-Ofelt theory and fit process of least square, the phenomenological intensity parameters Ωλ (λ=2,4,6) were obtained, In order to evaluate potential applications of Sm3+ ions in telluride glasses, the spectroscopic parameters: transition probability AR, branching ratio Br, radiative life time τr, emission pick cross section σλ for each band were calculated. The comparative studies with other Sm3+ doped different glasses showed that present glasses could be a potential candidate for lasers.Series of glasses based on (70-x) TeO2 – 20Na2O – xSm2O3 (x=0, 0.3, 0.6, 1, 1.2, 1.5 mol%) have been prepared using melt-quenching technique. The nature of the glass has been confirmed using X-ray diffraction; it is found that the glass samples are amorphous in nature. The thermal stability of the glass has been determined by means of Differential Thermal Analysis (DTA). From the DTA curve, the glass transition temperature (Tg), crystallization temperature (Tc) and melting temperature (Tm) have been identified and thermal stability is also calculated. The absorption properties of these samples are obtained by using UV-Visible-NIR spectrometer, the recorded absorption spectra exhibit nine absorption transition bands peaks corresponding to the transitions from ground level 6H5/2→6P3/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2. The emission characteristic of this glass is characterized using Photoluminescence (PL) spectroscopy at excited wavelength 404 nm, the emission spectra consisted o...

Impact of Annealing Time on the Optical Response of Zinc-Boro-Tellurite Glass

Annealing time dependent optical properties of melt-quench synthesized Er3+-doped (0.5 mol%) zinc-boro-tellurite (ZBT) glasses containing silver (Ag) nanoparticles (NPs) (1.0 mol%) are reported. Heat treatment (HT) durations are varied to control NPs growth. Reduction of NPs sizes from 12.7 to 6.6 nm for HT time beyond 6 hr at 410 °C is ascribed to their diffusion limited growth. Surface plasmon resonance bands evidenced at 550 and 580 nm are red shifted. Luminescence intensity enhancement is majorly attributed to the local field effect of Ag NPs and quenching is due to the energy transfer from NPs to Er3+. Present glass compositions are promising for the development of photonic devices.

Tuning surface plasmon in erbium-boro-tellurite nanoglass via thermal annealing

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 Ago 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 (2H11/2→4I15/2), 550 (4S3/2→4I15/2) and 632 nm (4F9/2→4I15/2). 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.

Influence of Er3+ dopants on optical properties of boro-tellurite glass

The effect of the rare earth ion concentration on the physical and spectroscopic properties of Er3+-doped boro-tellurite glass is studied. Glasses with compositions 30B2O3+10ZnO+(60-x)TeO2+xEr2O3 (where x=0, 0.5, 1, 1.5 and 2mol%) are prepared by melt-quenching method. The structural analyses are made through XRD, FTIR and UV-VIS-IR absorption spectroscopy. IR-spectra reveal five absorption bands in the region of 450-1500 cm-1 for different B-O and Te-O vibrational groups. The UV-VIS-IR spectra exhibits seven absorption bands corresponding to the transitions from 4I15/2 ground state to 4I13/2, 4I11/2, 4I9/2, 4F9/2, 2H11/2, 4F7/2 and 4F3/2 excited states. The bonding parameters are determined from the optical absorption spectra and are found to be covalent in nature. The optical band gap energy values corresponding to the direct and indirect allowed transitions decreases while the Urbach energy and cut-off wavelengths increases by the introduction of Er3+ ions. Keywords: Er3+ ions, melt-quenching, boro-tellurite glass, optical band gap