Indirect Optical Band Gap Research Articles

Effect of ZnO on Structural, Physical and Optical Properties of Heavy Metal Oxides Doped Tellurite Glasses

A conventional technique has been used to prepare Heavy Metal Oxides (HMO) doped ternary tellurite glasses. The batch composition of samples were as (90-y)%TeO2-10%WO3-x%ZnO, (y=5%,10%,15%, and 20%). ZnO alter the optical and physical properties of the glasses are investigated. The thermal characteristics of the produced samples are studied using differential scanning calorimetry, and their structural conformation is determined using XRD. The existence of structural units is shown by Raman spectroscopy. Other parameters of glass samples have been calculated, including density, molar volume, polaron radius, and intermolecular distance. The absorption spectra of samples were measured in the spectrum range of 350nm to 1000nm, and the refractive index, direct and indirect optical energy band gaps, and Urbach’s energy were determined.

Linear and non-linear optical properties of boron carbide thin films

Boron carbide films deposited by PECVD are subjected to post deposition vacuum annealing and plasma treatment for investigation of changes in the structure, linear and non-linear optical properties of the films. Deconvolution of core level XPES spectra of B1s, C1s and O1s indicates changes in the surface chemical states of the constituent atoms after post deposition treatments. Particle size estimated from XRD spectrum is found increasing from 135 to 140 nm after annealing. Envelop method is used to estimate refractive index, extinction co-efficient, and thickness from their measured optical transmission spectra in VIS-NIR region (400–1400 nm). The refractive index value is found to be 1.619, highest for the vacuum annealed boron carbide film. Direct and indirect optical bandgap remains same after vacuum annealing (Eg = 2.84), the plasma treatment causes a slight decrease in the bandgap. 5% decrease in film thickness is observed after post deposition annealing and plasma treatment owing to film densification. Energy loss in the medium measured in terms of tanδ and ELF’s reveals that the vacuum annealing of the film reduces the electromagnetic and electron energy loss in the film. Non-linear refractive index estimated using Ticha and Tichy relation exhibits similar trend as the linear refractive index spectra.

Studying spectroscopic, cyclic voltammetry, and electrical properties of novel 4-amino antipyrine derivative for photonic applications

The present work aims to synthesize a new antipyrine derivative and then study its optical properties in the form of thin films with the aim of using the obtained results in the fabrication and designing of new optoelectronic devices. A N1,N3-bis(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)malonamide, dpdp novel organic compound has been successfully synthesized in dimethylformamide (DMF) medium by the chemical reaction between 4-aminoantipyrine and malonyl chloride. The obtained dpdp compound is characterized quantitatively and qualitatively by using micro elemental analysis, FTIR spectroscopy, 1H– & 13C–NMR, and thermogravimetric measurements. Two steps weight loss of 84 % (calcd. mass loss 37.25 %) is recorded in the temperature range of 25 °C to 800 °C. Thin films of the novel organic dpdp were successfully grown by the thermal evaporation technique. FSEM images show the surface topology of the as-deposited thin film which is characterized by high quality, continuous, and crystalline granular surface with an average particle size of 70 nm. The cyclic voltammetric analysis showed that the energy difference between the HOMO and LUMO equals 2.43 eV. The calculated values of the optical band gap transitions deduced from the diffuse reflectance spectra are found to be 2.27 eV, and 3.44 eV for the powder and the as-deposited dpdp thin films, respectively. The photoluminescence spectra analysis showed that the as-deposited film dpdp is characterized by a main green peak centered at 530 nm. The optical transflection spectra showed that the calculated values of the indirect optical band gap transitions are found to be 3.53 eV for the as-deposited thin film which slightly increased to 3.63 eV after annealing at 373 K and 423 K for 4 h. Spectral variations of the refractive index and the specific polarizability showed one peak around 400 nm which fades by annealing treatment at 373 K and 423 K. The dc electrical resistivity activation energy of the free charge carriers was estimated.

Combined experimental and TD-DFT/DMOl3 investigations, optical properties, and photoluminescence behavior of a thiazolopyrimidine derivative

We present here the FT-IR, DFT computation, XRD, optical, and photophysical characterization of a heterocyclic compound with thienopyrimidine and pyran moieties. TD-DFT/DMOl3 and TD-DFT/CASTEP computations were used to study the geometry of isolated and dimer molecules and their optical behavior. The indirect (3.93 eV) and direct (3.29 eV) optical energy bandgaps, HOMO–LUMO energy gap (3.02 eV), and wavelength of maximum absorption (353 nm) were determined in the gas phase with M062X/6-31+G (d, p). A thin film of the studied molecule was studied using XRD, FT-IR, and UV–Vis spectroscopy. The average crystallite size was found as 74.95 nm. Also, the photoluminescence spectroscopy revealed that the compound exhibited different emission bands at the visible range with different intensities depending on the degree of molecular aggregation. For instance, solutions with different concentrations emitted blue, cyan, and green light. On the other hand, the solid-state material produced a dual emission with comparable intensities at λmax = 455, 505, and 621 nm to cover the entire visible range and produce white emission from a single material with CIE coordinates of (0.34, 0.32) that are very similar to the ideal pure white light. Consequently, these findings could lead to the development of more attractive new luminous materials.

Optical and structural characteristics of pulsed DC magnetron sputtered Ce1−xTixOy coatings

This contribution investigates the impact of adding transition metal of Ti to CeOy samples at various concentrations referring to 0, 15.84, 24.46, 34.46, 36.23, 38.46, 45.38% and pure TiOy, correspondingly. The samples were fabricated by the magnetron sputtering technique. X-ray diffraction (XRD) configurations demonstrate the presence of α-Ce2O3 and Ce2O3 phases with increased Ti contents in the systems. X-ray photoelectron spectroscopy (XPS) experimentation confirms the purity of the S1-sample (CeO2) and the purity of the S8-sample (TiO2). Further XPS analysis reveals that Ti incorporation in the doped systems functions as a reducing agent because of the existence of α-Ce2O3 and Ce2O3 phases. Moreover, based on UV–vis spectroscopy results, the studied samples exhibit indirect optical energy band-gaps reduced from 2.6 to 2.35 eV with the increase of Ti concentrations of 0–45.38% in (S1-S7), respectively. In reference to bandgap 2.35 eV, a slight rise in band gaps was detected for S3 sample. However, an observable increase in the band gap of 2.9 eV occurred for S8 (pure TiO2). Optical analysis of the calculated energy loss parameters demonstrates that all the studied samples reveal small amounts of energy loss. Our results suggest that the improved optical properties of Ti-doped CeOy films could serve for various optical applications.

Influence of nanocomposite (1-x)CdS/xCuS on optical characteristics of PVA/CMC/PEG blended polymer; effect of ratio (x)

PVA/CMC/PEG blended polymers loaded with (1-x)CdS/xCuS nanocomposites (x = 0, 0.3, 0.5, 0.7, 1) were formed applying the thermolysis and casting techniques. Rietveld analysis of synchrotron x-ray diffraction data measured for (1-x)CdS/xCuS manifested a single hexagonal phase CuS (x = 1.0) and biphasic structure, hexagonal and cubic, for CdS (x = 0.0); composite samples (x = 0.3, 0.5, and 0.7) exhibited the three phases with varied percentages. Average crystallite size for all nanofillers ranged 4–12 nm. The surface morphology and chemical compositions of the different blends were investigated using SEM and EDS techniques. The effect of loading PVA/CMC/PEG blends with multi phases CdS–CuS nanocomposite on the optical linear and nonlinear behaviors was explored using diffused reflectance technique. The direct and indirect optical band gaps (Eg) values determined for PVA/CMC/PEG are 5.62 and 5.18 eV, respectively, which reduced to (4.2, 4.5, 4.47, 4.56, 3.89) and (3.43, 3.9, 3.74, 3.98, 3.18) eV upon loading with (1-x)CdS-xCuS for x = 0, 0.3, 0.5, 0.7, and 1, respectively. The refractive index of all loaded blends increased non monotonically with (x) reached its highest value for λ ≥ 500 nm upon loading with x = 0.0 (CdS). The fluorescence (FL) intensity of the blended polymers nearly quenched upon loading with CuS (x = 1.0) and greatly enhanced for x = 0.5.

Structure and tunable broadband near-infrared luminescence of Cr3+ in borophosphate glass

In this work, a series of Cr3+ ion-doped borophosphate glasses were prepared by the melt-quenching method. The structure, optical absorption, and near-infrared luminescence properties of the borophosphate glasses were investigated in detail. The results showed that Cr2O3 plays a modifier role in borophosphate glass consisting of borate and phosphate groups. The indirect optical bandgap and Urbach energy were found to vary in the range of 3.293–3.344 eV and 0.290–0.394 eV, respectively. Meanwhile, the Cr3+ ions located in a weak crystal field environment were confirmed by a Dq/B value of less than 2.3. Under the excitation of 440 nm, the as-prepared glasses exhibit broadband near-infrared (NIR) luminescence with an FWHM of about 210 nm and demonstrate a significant spectral red-shift from 858 nm to 894 nm. When the Cr2O3 content is greater than 0.30 mol%, the fluorescence intensity appears obvious concentration quenching. This work illustrates the potential application prospects of Cr3+ ion-doped glass materials as broadband NIR fluorescent devices.

Effect of annealing temperature on the optical characteristics of Se80Te15Ge5 films for opto-electronic applications

An evaporation process was used to deposit Se80Te15Ge5 thin films. The annealed films are amorphous below 373 K and polycrystalline above 423 K, according to X-ray diffraction measurements. Optical constants for these films were calculated at 323,373 and 423 K annealing temperatures. The single oscillator model is used to investigate the refractive index. The nonlinear refractive index and third-order nonlinear susceptibility are calculated. The absorbance coefficient was computed, revealing an indirect optical band gap value that decreases with annealing temperature. This decreases as the annealing temperature rises.

Bath temperature role in tailoring the properties of chemically bath deposited tin sulfide films

In this paper, the structural, optical and electrical properties of tin sulfide thin films are reported. Thin films are deposited (at different bath temperatures) by chemical bath deposition to investigate the role of bath temperature on the film properties. X-ray diffraction patterns reveal the structural phase transition from cubic to orthorhombic at 75 ºC bath temperature. FTIR spectra of cubic and orthorhombic films confirm dominant bond stretching of sulfur (S) and tin (Sn) atoms. Films deposited at different bath temperatures exhibit homogeneous and uniform surface morphology with surface roughness ≤ 45 ± 3 nm. Optical characterization shows that the cubic phase films have direct energy band gap (Eg) which is observed to be decreased (2.20 eV to 1.76 eV) with increasing bath temperature (55 ºC to 65 ºC). At 75 ºC bath temperature, the obtained film crystallizes in orthorhombic crystal structure and has an indirect optical energy band gap, Eg = 1.04 eV. A remarkable decrease in energy band gap is observed which is due to the structural phase transition (from cubic to orthorhombic) at 75 ºC bath temperature. Cubic and orthorhombic SnS films have electrical resistivity ρ ≤ 2.123 × 103 Ω.cm. Bath temperature is observed to play an important role in tailoring the crystal structure and energy band gap of chemically bath deposited tin sulfide thin films. Results suggest that the tin sulfide films can be deposited with required combination of properties for optical and energy harvesting devices.

AInSn2S6 (A = K, Rb, Cs)─Layered Semiconductors Based on the SnS2 Structure.

RbInSn2S6 and CsInSn2S6 are yellow two-dimensional (2D) semiconductors featuring anionic SnS2-type layers of edge-sharing (In/Sn)S6 octahedra. These structures are directly derived from the parent structure of SnS2 by replacement of Sn4+ atoms with A+ and In3+ atoms. The compounds crystallize, isotypic to the ion-exchange material KInSn2S6. They adopt the triclinic space group R3̅m (no. 166). The compounds have similar indirect optical band gaps of 2.31(5) eV for Rb and 2.47(5) eV Cs. The measured work functions for each material are ∼5.38 eV. The density functional theory-calculated effective mass values exhibit strong anisotropy due to the 2D nature of the crystal structures and in the case of CsInSn2S6 for hole carriers along the a, b, and c crystallographic directions are 0.30 m0, 0.34 m0, and 2.54 m0, respectively, while for electrons are 0.06 m0, 0.07 m0, and 0.47 m0, respectively.

An imidazole ligated zinc(II) transition metal complex as a “turn-off” fluorescent sensor for the selective and sensitive detection of brilliant blue FCF

Synthetic colors play a significant role in the food industry and processing sector whereas food safety incidents caused by the illegal addition of colors have gotten more successive. In this study, a highly selective novel zinc incorporated imidazole based metal complex (ZL1) was developed from ligand 2-[(1H-imidazole-2-ylmethylene)-amino]-4-methyl-phenol (L1) in 1:2 (metal:ligand) molar ratio. It was characterized quantitatively using standard spectroscopic techniques. The vital fluorescence properties such as stokes shift, lifetime and quantum yield values were evaluated for the rapid and non-destructive detection of brilliant blue FCF (BB) by the inner filter effect where the emission spectra of ZL1 were overlapped with the absorption spectra of BB. In the presence of BB, a bright yellow colored solution of ZL1 with an emission at 570 nm was quenched with a peak shift observed at 540 nm. It also illustrated the lower detection limit of 2.67 × 10-8 M in the linear range of 1 × 10-6 M to 5 × 10-6 M under optimal conditions. To attain more idea about the properties of a compound, indirect optical band gap energies (Eg) were found using a tauc plot. Encouragingly, the non-toxic property of ZL1 towards myogenic cell line H9c2 was done using a cytotoxicity study and showed excellent photostability. The theoretical approach for geometry optimization, vibrational band assignments, frontier molecular orbitals, and absorption spectrum of the ZL1 were investigated by DFT/B3LYP/6–311 + G(d,p) methods. The theoretical ultraviolet and infrared spectrum of the complex was obtained in vacuum state. Also, the elucidation of the quenching mechanism of fluorescence sensing was proposed with the help of cyclic voltammetry studies. In addition, the practical application of ZL1 was applied to access the BB in food samples showing its potential in food quality control in the future.

SPR coupled luminescence enhancement of Er3+/Au NPs -doped multicomponent tellurite glasses

Glasses of the composition (59.6-x)TeO2+10K2O+10P2O5+10B2O3 +10ZnF2+0.4Er2O3+xAu2O3 (x = 0.1, 0.2, 0.3 and 0.4 mol%) were produced by means of melt-quenching method and thoroughly analyzed using EDS, XRD, TEM, DSC, UV–Visible–NIR absorption and photoluminescence (PL) techniques. These Au incorporated glasses were investigated for their surface plasmonic resonance (SPR) coupled luminescence enhancement. The plasmonic absorptions of gold have been evidenced through the presence of absorption bands at 599 nm and 652 nm. Direct and indirect optical band gap and the urbach energies were estimated from the absorption spectra. Well dispersed nanoparticles having an average size of 10 nm was verified by TEM analysis. Plasmonic coupled enhancement in the characteristic emission of Er3+ ions and in other spectral parameters were traced and quantified. The visible as well as NIR emission spectra, Judd-Ofelt spectroscopic parameters and other critical spectroscopic properties were computed, which were further characterized via CIE diagram to analyse the suitability of the prepared glasses for optical applications. The studies revealed that the prepared glasses impart enormous scope in the field of solid-state lasers and color display devices.

Tailoring the structural and optical properties of HiPIMS TiO2 thin films for photovoltaic applications

Titanium dioxide (TiO2) thin films are deposited onto glass and silicon <100> substrates by high power impulse magnetron sputtering (HiPIMS) at various substrate positions from the substrate-holder center (x = 0, 10, 20 and 30 mm). The structural analysis conducted through XRD and Raman spectroscopy shows that all the films deposited at lower radial distance (x = 0–20 mm) are identified as pure anatase phase of TiO2, while those deposited at 30 mm contain a small trace of rutile phase with anatase phase remaining dominant. AFM analysis reveals homogenous surfaces with low values of roughness (2.6–3.8 nm) and a decrease of grain size with the substrate position. The films exhibit high refractive index and large indirect optical band gaps (3.25–3.38 eV). Finally, UV-blocking and antireflection characteristics are studied.

Physico-Chemical Properties of TiO2 Coatings Derived From Acid Catalyst-Free Precursor via Spin Coating

The present method of producing titania (TiO2) coatings involves the addition of an acid catalyst to prolong the shelf life of the initial precursor. However, this method has complex chemical routes that favor rutile TiO2 and result in higher bandgap energy. In this current work, unheated and heated TiO2 coatings were successfully prepared via spin-coating using an acid catalyst-free titania precursor. The TiO2 coatings were thoroughly investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman, Fourier transformed infrared (FTIR), and UV-Visible spectroscopic techniques. From XRD and Raman data, the unheated coating is amorphous, while the heated sample consists of anatase polymorph of TiO2. The FTIR results revealed traces of organic residues for the heated sample due to the organic nature of the precursor used. SEM showed that both samples were not uniform, porous, and consisted of spherical micro/nanostructured particles with some aggregation ascribed to the nature of the precursor. Diffuse reflectance indicated an absorption band edge at the UV region and showed similar absorption spectra to commercial TiO2 powder. However, a redshift of the UV-Vis reflectance spectra of the heated sample was observed. Using the baseline approach, the indirect optical bandgap of the unheated TiO2 coating decreased from 3.31 to 3.26 eV (± 0.2 eV) after the heat treatment, which is due to the crystallization of the sample into anatase TiO2.

Optical band gap and luminescence study of yttrium doped neodymium lead borotellurite glass system

"Glasses of composition (49-x)H3BO3-35TeO2-15PbO-1.0Nd2O3-xY2O3 (x = 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) were successfully prepared by a melt-quench method. The effect of Y2O3 on the optical properties of the glasses were investigated by using Uv-Vis NIR and photoluminescence spectroscopy. X-ray diffraction pattern of the prepared glasses exhibits amorphous nature. Absorption spectra of the glasses are recorded in the range 400 – 1100 nm and shows eleven absorption peaks. In order to determine the optical band gap of the glass sample, the Uv-Vis NIR measurement has been carried out in the room temperature. The values of direct and indirect optical band gap initially decreasing before increasing, which were attributed to structural changes induced by the inclusion of Y2O3. The luminescence spectra were obtained under 581 nm wavelength."

Photoluminescence downshifting studies of thermally stable Dy3+ ions doped phosphate glasses for photonic device applications

Trivalent dysprosium (Dy3+) activated barium zinc lithium phosphate (BaZnLiP) glasses were prepared by employing melt quench routes. To understand the possible applicability of the prepared glasses in photonic device applications, numerous structural, optical, and radiative characteristics have been explored in detail. The non-crystalline character of BaZnLiP glass has been confirmed with the help of an X-ray diffraction pattern. The titled glasses doped with Dy3+ ions show several absorption peaks in the 330–1800 nm range with an indirect optical band gap of 3.41–3.76 eV. The Judd-Ofelt (J-O) theory was employed on the absorption profiles and estimated various radiative parameters for the Dy3+ ions activated BaZnLiP glasses. The Dy3+ ions activated glasses exhibit intense excitation at 350 nm and three sharp visible emissions at blue (4F9/2 → 6H15/2), yellow (4F9/2 → 6H13/2), and red (4F9/2 → 6H11/2). To ascertain the lasing potentialities of BaZnLiP glasses, the stimulated emission cross-section and branching ratios have been assessed by correlating the emission spectral information with the radiative parameters calculated from the absorption spectral features. The colorimetric properties show the coordinates situated in a bright white region. Temperature-dependent photoluminescence (TD-PL) spectral features recorded revealed the thermal stability of the as-prepared glasses. The explored distinctive features for Dy3+ ions activated BaZnLiP glasses suggested the superiority and direct utility of the as-prepared glasses in advanced photonic device applications such as lasers and w-LEDs.

Role of rubrene additive for reinforcing the structural, optical, and dispersion properties of polyvinyl alcohol films towards optoelectronic applications

A conventional casting method was used to produce promoted polyvinyl alcohol (PVA) films via rubrene additive. The 1.2 g of PVA dissolved in 120 ml of distilled water and doped with various concentrations (0, 0.1, 0.3 and 0.4 wt%) of rubrene dye. The influence of rubrene dopants on the structural properties of PVA was studied using FTIR and XRD techniques. The semicrystalline nature of the PVA polymer was established by the XRD pattern. FT-IR analysis shows changes in peaks intensities of PVA and their widths are expanded in the presence of rubrene dopants which indicates the interactions between the functional groups of PVA and the rubrene dopants. XRD patterns exhibit the existence of rubrene inside the PVA structure leads to form cross-linking which enhances the amorphous nature within the doped PVA samples. The optical characteristics were investigated using spectrophotometric measurements of transmittance T(λ), reflectance R(λ), and absorbance A(λ) in the spectral range of 200–2500 nm. The indirect and direct optical band-gap values of PVA films decreased from 5.15 eV and 5.69 eV to 3.63 eV and 4.50 eV as rubrene doping ratio was increased from 0 to 0.4 wt%, respectively. The refractive index dispersion region was explained using the single oscillator (Wemple–DiDomenico) model. The extracted values of dispersion energy (Ed), dielectric constant at infinite frequency (ε∞) and lattice dielectric constant (εL) of PVA/rubrene composite films increased from 0.74 eV, 1.31 and 1.35 to 5.35 eV, 3.47 and 4.35; respectively, whereas oscillator energy (Eo) decreased from 2.41eV to 2.17 eV as rubrene contents increased from 0 to 0.4 wt%, respectively. Indeed, these changes in values of dispersion parameters is evidence to the cross-linking bonds between the host polymer and the rubrene dopants. The improvement of optical properties of PVA/rubrene films demonstrates their applicability as eco-friendly packaging materials, particularly in flexible optoelectronic and microelectronic devices.

Architecture of a dinuclear Co(II) complex based on 3-amino-1,2,4-triazole-5-carboxylic acid: molecular structure, thermal behavior, optical properties, and DFT calculations

The dinuclear compound [Co2(Hatzc)2(H2O)6](NO3)2·4H2O containing the polytopic ligand Hatzc‒ = 3-amino-4H-1,2,4-triazole-5-carboxylate was synthesized and characterized. Single-crystal X-ray diffraction showed that two monoanionic N,O-chelating Hatzc‒ ligands bridge two Co(II) ions in a µ-N1,N2 fashion. Both Co(II) centers are further coordinated by three H2O ligands making up an octahedral coordination. A complex network of intra- and intermolecular O‒H···O and N‒H···O hydrogen bonding interactions characterize the structure. Hirshfeld surface analysis, ATR–FTIR, and FT-Raman spectroscopy in combination with density functional theory (DFT) calculation of vibrational modes confirm this multitude of H bonds. Thermogravimetric and differential thermal analysis experiments under an argon atmosphere in the temperature range of 25–900 °C showed thermal stability till about 100 °C and multi-step decomposition yielding Co2O3 at about 280 °C. The octahedral environment of Co(II) was confirmed by UV–vis absorption spectroscopy, which shows weak absorption bands at around 520 nm assignable to electronic d‒d transitions alongside with π‒π* transitions dominating the 250–350 nm range. Time-dependent DFT calculated excited states agree very well in terms of energy match with the observed transitions. The direct and indirect optical band gap values were determined using the Tauc plot method to 3.33 eV and 2.75 eV, respectively, indicating semiconducting properties.

Modifications of optical, structural, chemical and morphological properties of molybdenum disulfide (MoS2) sputtered thin films under high dose gamma radiation

Molybdenum disulfide (MoS2) is considered to be a promising member of Transition metal dichalcogenides (TMDCs) displays significant physical and chemical peculiarities that make it promising candidate for extensive applications in nano and micro optoelectronic device applications, energy harvesting and light and gas detection devices. In the present work, we illustrated the influence of gamma ray irradiation on optical, morphological, structural and electronic peculiarities of 2D MoS2 thin films. 2D MoS2 thin films were grown by DC sputtering technique. The synthesized thin films samples were exposed to gamma radiation with 1500 kGy dose. There are significant structural and morphological alterations occur in thin films of MoS2 after exposure to gamma irradiation. From the absorption spectra Urbach energy, indirect optical band gap energy, absorption edge, and extinction coefficient were calculated. Alterations that occur in optical, structural, morphological and electronic parameters after the exposure of gamma irradiation have been corresponding with radiation instigated compositional and structural defects. The peculiarities of virgin and gamma exposed MoS2 thin films with 1500 kGy gamma-ray dose from Co-60 source were studied by UV spectrophotometer, X-ray diffraction (XRD), Rutherford Backscattering Spectroscopy (RBS), X-Ray photoelectron spectroscopy (XPS), Photoluminescence (PL) spectroscopy, Atomic Force Microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR).

DC conductivity, optical properties and Judd-Ofelt evaluation of 20Li2O-xBi2O3-(78-x)TeO2-1Er2O3-1Ag mixed ionic-electronic glasses

20Li2O-xBi2O3-(78-x)TeO2-1Er2O3-1Ag glass system was prepared by melt quenching, and its DC conductivity, optical and spectroscopic properties were investigated. Its amorphous nature was confirmed by x-ray diffraction analysis. Results showed that DC conductivity σdc initially increased at x < 7 mol% and then decreased to a minimum at x = 11 mol% Bi2O3. UV–vis–NIR absorption spectra indicated six transition bands centered at 1496, 979, 799, 653, 544, and 521 nm corresponding to 4I13/2, 4I11/2, 4I9/2, 4F9/2, 4S3/2, and 2H11/2 Er3+ transitions, respectively. Analysis on optical absorption edge by Tauc’s plot revealed maximum in direct Eoptd(3.609 eV) and indirect optical energy bandgap Eopti(3.259 eV) at x = 11 mol%. Judd–Ofelt intensity parameter Ω2was calculated from optical absorption data to describe the intensity of electron transitions within the 4 f shells of Er3+ ions in the glasses. A minimum Ω2 was obtained at x = 11 mol%. The minimum values of σdc and Ω2 at x = 11 mol% are related to the presence of high bridging oxygen in the mixed ionic-electronic region that influences the symmetry of surrounding Er3+ ions.