shown that increasing of antimony sulfoiodide (SbSI) content in the glass composition and the temperature increase lead to shift in the absorption edge towards long-wavelength range. The optical absorption edge E g α positions are determined. The slope change observed for the absorption edge in the temperature range of T g ÷ T c is conditioned by generation of nanocrystals of
3.1 MAXWELL’S COUNTING FOR FLOPPY MODES &AVERAGE COORDINATION NUMBER According to J. C. Phillips it may be valuable to consider the transitions between Z = 2.4 and 2.67 in the light of the constraint – counting argument originally proposed for amorphous covalent materials . Phillips gave the mechanical- constraint counting algorithms to explain glass forming tendencies. The strongest covalent forces between nearest neighbours serve as Lagrangian (mechanical) constraints defining the elements of localstructure (building blocks). Constraints associated with the weaker forces of more distant neighbours must be intrinsically broken leading to the absence of long-range order. The well known Phillips–Thorpe approach is based on comparing the number of atomic degrees of freedom with the number of inter-atomic force field constraints. If the number of degrees of freedom is greater than the number of constraints, the network is “floppy”; conversely, if the network becomes over-constrained, stressed-rigid structures will percolate throughout the entire network. According to Phillips, the tendency of glass formation would be maximum when the number of degrees of freedom exactly equals the number of constraints. For the composition Ge 10 Se 90-x Sb x (x = 0, 3, 6, 9, 12, 15, 18, 21, 24). The average coordination number Z was
Particularly, NPs can increase the yield of their weak optical transitions by generation of intense electric fields upon electromagnetic excitation where plasmonic metal nanostructures in the vicinity of the rare-earth (RE) ions alter their free space spectroscopic properties (Som and Karmakar 2008). This mechanism so-called nanometal enhanced fluorescence (NMEF) and it is due to the localized surface plasmons resonance (LSPR). Three main phenomena that govern the origin of the electromagnetic field enhancement are; the localized surface plasmons (LSP), the change of confinement at the metallic nanoparticles extremities and coupling the effect (Guillot and Chapple 2012).The metal nanocluster exhibited delocalized conduction electron which give absorption in the visible region due to intraband transitions (Udayabhaskar et.al., 2014). Thus excitation near to resonant value of the SPR is ascribed to the amplified local field. Due to this phenomenon, it is reported that energy transfer (ET) between ions RE and NPs is possible (Awang et.al., 2014). Thus nanoparticles would be the enhancer or quencher to the fluorescence of samarium ions in this glass. Therefore, this study will focus on the opticalproperties of the samarium ions for an optical tuning of the solid state luminescence materials.
Glass is an often-misunderstood material; in the general public lexicon, glass usually refers to soda lime silica type glasses, namely windows and drinking glasses. However, in the technical sense glass refers to a state of matter and is not specific to any particular material, element or compound. Glasses exist in metallic [99,100], organic [101–103] and non-silica based systems . While there are multiple definitions of a glass, the current definition of ‘glass is a non-equilibrium, non-crystalline condensed state of matter that exhibits a glass transition. The structure of glasses is similar to that of their parent supercooled liquid (SCL) and they spontaneously relax towards their SCL state. Their ultimate fate, in the limit of infinite time, is to crystallise’  is the most comprehensive definition to date. The formation method to produce the glass is not a defining metric either, glasses can be produced from the traditional melt quench method, or more modern sol-gel [106–108] or vapour deposition methods . Glass has been the driving technology for vital research in many disciplines, including biology (microscope lenses), chemistry (glassware), and astronomy (telescope lenses).
Enhancing the luminescence intensity and optical gain by inhibiting the concentration quenching effects remains challenging. Since the concentration quenching in the single rare earth doped materials limits their emission cross-section, the efforts have been tuned to increase the emission cross section of RE ions by developing co-doping methods (Guo et al., 2010; Silver et al., 2001). In this way, energy transfer mechanism between two different rare earth ions in the host would contribute to enhance or quench the visible emissions. Although there are some reports on co-doped tellurite glasses, but there is no report about the thermal structural and optical characterization of Sm 3+ /Yb 3+ co-doped sodium tellurite glasses. Controlled co-doping for the enhancement of luminescence and emission cross section are not well studied especially for (79.5-x)TeO 2 -20Na 2 O-xSm 2 O 3 -0.5Yb 2 O 3 , where x= 0, 0.5, 1.0, 1.5
prepared by sol-gel method. The amorphous nature of glasses are characterized using X- ray Diffraction (XRD) technique while the actual glass composition is determined using the Energy Dispersive of X-ray Analysis (EDAX). Meanwhile, the optical energy gap (E g ), Urbach energy (∆E) and the refractive index of glass are studied using UV-Visible
The structure of the as-quenched and annealed samples was examined by X-ray diﬀraction (XRD) measurements with Cu-K radiation (40 kV-40 mA). The local atomic structure was studied by ordinary XRD measurements with mono- chromatic Mo-K radiation operated at 45 kV-150 mA produced by a rotating anode X-ray generator. The observed diﬀraction proﬁles were corrected by air scattering, polar- ization, absorption and Compton scattering and then, con- verted to electron units per atom by the Krog-Moe-Norman method 13) to obtain an interference function, QiðQÞ estimated from the coherent scattering intensity in absolute units. The ordinary RDF was led by Fourier transformation of the QiðQÞ. The coordination number and interatomic distance between the constituent elements were calculated by ﬁtting the QiðQÞ and RDF with non-linear least square ﬁtting method. EXAFS measurements for the analysis of the local environments were performed on beam line BL-12C at the Photon Factory of the Institute of Materials Structure Science, High-Energy Accelerator Research Organization (KEK), Tsukuba, Japan and beam line BL-01B1 at SPring-8, Hyogo, Japan. All measurements were done in transmission geometry at room temperature. Measured spectra were analyzed using the program REX 2000 (Rigaku Corp.).
melt-quenching technique. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction. Optical absorption and fluorescence spectra were recorded at room temperature for all glass samples. The various interaction parameters like Slater-Condon, bonding and Lande’s parameters have been computed. Judd-Ofelt intensity parameters and laser parameters have also been calculated. The values of spontaneous emission probability (A) and stimulated emission cross-section( σ p ) are
(MO= ZnO, CaO and CdO) were prepared by conventional melt quenching method. The amorphous nature of these glasses was confirmed by X-ray diffraction. Differential scanning calorimetry analysis revealed reasonably good forming tendency of the glass composition. FTIR spectra were used to analyze the presence of BO 3 and BO 4 functional groups in the glass. Optical absorption spectra of these
This system study was carried out by systematically replacing calcium oxide with magnesium oxide to determine the effect o f replacing an ion with one o f the same valence, but with a differing ionic radius and to determine how this affects the solubility behaviour. It clearly demonstrates that the CaO content plays a major contribution in terms o f solubility behaviour. It can be seen from the curves that by systematically replacing CaO with MgO, the solubility curves lose their exponential nature. This might be deduced as evidence that CaO makes a significant contribution to controlling the solubility process more than for example sodium oxide or potassium oxide. This system has been calculated as 32 mol% o f valence oxide in total. A Ca 32 Na 23 P 45 ternary glass has a solubility value o f 1.00 x 10*06 g.cm'^.h'% which is lower (dissolves less quickly) than the glasses o f the corresponding magnesium quaternary system. This effect can not necessarily be explained by the fact o f Mg^"^ being the lighter ion (Ca 40.1g/mol Mg 24.3g/mol) (24). If that would be the case solubility values should be smaller. It might be the case that the magnesium ion is smaller and hence is able to leach through and out o f the glass structure more easily and therefore account for the higher weight loss and higher number.
It is well-known, the main reasons for the large Ω 2 values are the high degree of covalence between Dy 3+ and oxygen ions and the low symmetry (or the high disorder) of the coordination structure surrounding the Dy 3+ ion. The later is related directly with the B/Te content ratio. When the B/Te ratio increases, the coordination sphere around Dy 3+ is changed to the higher disorder due to more non-bridging oxygen ions and existence of the BO 4 → BO 3 conversion.
Binary glasses with the composition 40BaO-(60-x) B2O3: x Sm2O3 for x = 0 and 0.5 mol % were prepared by the melt-quenching technique. The prepared glass samples were characterized by optical absorption and photoluminescence spectra were recorded at room temperature. From the optical absorption studies it is found that five transitions from 6H5/2 → 4I11/2, 6P5/2, 6P3/2, 6P7/2 and 4D3/2 were observed at wavelengths 486 nm, 401 nm, 375 nm, 360 nm and 343 nm respectively. From the observed absorption edges optical band gap, the Urbach energies were calculated. The luminescence spectra exhibited conventional orange -red emission bands at around 563 nm, 600 nm, 647nm and 712nm corresponds to the 4G5/2 → 6H5/2, 6H7/2, 6H9/2 and 6H11/2 transitions respectively. The emission spectrum was observed under various excitation wavelengths. The emission spectrum measured is characterized through Commission International d'Eclairage (CIE) 1931 chromaticity diagram to explore its suitability for display and w-LED applications.
passivation of dangling bonds, resulting in a range of Si-QD size from 2.5 to 3 nm (estimated by X-ray diffraction). A low energy implant leaves the Si implant concentration peak near the vacancy peak . This fact means that during the annealing process Si-QDs are forming in a region of high defect concentration, in turn the formation of stoichiometric oxide is retarded, meaning a higher concentration of sub-oxide states will remain, as compared to higher energy implanted samples. Chen et al. report the observation of all four oxide states (not seen in this work), which is evidence of structural disorder, assuming the same branching ratio and spin- orbit split as reported here. We estimate from their work a BE shift for the n=1,2,3,4 oxide states from pure Si of +1.2, +2.5, +3.6 and +4.5 eV, respectively, which are all larger than the standard values mentioned in Sec. 7.3. Using the same charge correction procedure as this work, Chen et al. find no shift between QD sizes, while they do see all samples shifting to a lower BE from the reference Si-sample by ≈ 0.6 eV. As Chen et al. does not give a clear account of this shift in BE, we assume that the presence of structural disorder is to account for this phenomena.
The very high sensitivity and elemental specificity afforded by X-ray absorption spectroscopy makes it an excellent method for studying the composition and electronic structure of complex systems such as GZNO solid solutions. Hard X-ray spectroscopy was employed to study the local chemical environment of Ga and Zn in GZNO solid solution nanocrystals. At both zinc and gallium K-edges the X- ray cross section (σ) is small, hence the penetration depth of hard X-rays is much greater than the sample thickness (nanocrystal diameter) and the bulk properties of the GZNO samples are being probed at these energies when collected in transmission and fluorescence detection modes, and there is usually little saturation effect since the appropriate sample thickness can easily be prepared. The Ga and Zn K-edges measure the 1s →np transitions (n ≥ 4 for Zn and Ga) and are highly sensitive to oxidation state and local chemical environment of the absorbing atom. Since Ga and Zn are neighbours in the 3rd row of the periodic table (Zn Group 12 and Ga Group 13), their absorber atom phase shift is very similar; also, O and N have a very similar back scattering phase (nearly linear in k space) and monotonic backscattering amplitude. We would expect that in an ideal solid solution the absorption edges of Ga and Zn would be nearly identical as both absorbers would exist in the same chemical environment, in this case a wurtzite structure containing a distribution of N and O nearest neighbours. In a non-ideal solid solution we would expect the minor
In recent years, the nonlinear opticalproperties of glasses containing metal nanoparticles (NPs) were studied extensively [1-5].These materials are of great interest with respect to both the physics of low- dimensional structures and their application for various nonlinear devices. Metal NPs-doped glasses have been used with particular success for generation of ns and ultrashort pulses in visible and near-infrared solid-state lasers.These nanocomposite glasses can be prepared through various techniques like the sol–gel , melt- quench , ion implantation  and ion-exchange  methods etc. Among these, melt quench technique is one of the oldest, conventional and most successful techniques. Further, metal NPs have gained a lot of attention because of their optical nonlinearities, which are substantial due to the surface plasmon resonances (SPR) lying in the visible region. The dispersive third order nonlinear susceptibility χ (3) of metal nanoclusters are very strong when excited near the SPR due to the local field enhancement effect . Recently, J M P Almedia et al.  and B Karthikeyan et al.  and many others have been studied the nonlinear opticalpropertiesglasses containing metal nanoparticles at the wavelength corresponding to SPR under different pulse excitations. In particular, gold NPs have drawn much intension due to its high third order nonlinearity and fast response time as compared to silver and copper. In present paper, we investigate the nonlinear opticalproperties gold doped sodium triborate glasses prepared by melt quench technique at the wavelengths corresponding to SPR of Au NPs using ns pulses.
oxides improve the glass forming nature. Because of these properties, it has numerous applications in solid state devices, electro chemical, electro and electric optical devices . Transition metal ions are generally carried out as probes in glasses to give valuable information about electronic states and local structures with the aid of spectroscopic techniques . Zinc Oxide, an II-VI compound semiconductor with a huge band gap of about 3.4 eV and a large substantial binding energy (~60 meV), is a prominent material in optical devices which include blue, violet & UV- LEDs and LDs (Laser Diodes) . Due to its low melting point, they have been used as good sintering agent. The best transparency in a mid infrared region, lowest phonon energy (~550cm -1 ) and high refractive index (~2.3) of heavy metal oxides are best for photonics and optical communication network . Borate is an appropriate optical material as it is having more transparency, low melting point, high thermal stability and good solubility . _________________________________
The energy dispersive X-ray diffraction was carried out in IWCA 200 system connected to a LEO – stereo scan 440 scanning electron microscope. EDAX spectra of KAP, Co: KAP, Ni: KAP are shown in Fig.3a, 3b and 3c respectively. The atomic percentage of metals in each crystal is indicated in table 2. The level of Co and Ni doping in KAP is observed to be nearly equal. This reveals that KAP has nearly the same driving force to take in either Co or Ni in the same quantities in the crystal lattice. This appears to be true, because the
The value of experimental third order nonlinear susceptibility values  were found to be in the range (1.49- 3.04) x10 -13 esu, but the values of theoretical third order nonlinear optical susceptibility for all the studied sample, were found to be in the range (2.46-9.02) x 10 –13 esu, this means that all the studied samples are probably good candidates for nonlinear optical applications . Also, we found that third order nonlinear susceptibility increases with decreasing the optical energy gap and increasing the refractive index as is evident in figure 2 and figure 3.
mixture was then melted in a porcelain crucible at 950 0 C by placing in a muffle furnace. The homogeneous melt was quickly quenched between two brass plates. Glass samples of about 2mm thickness were obtained. Powder XRD measurements were carried out by using Philips X’Pert pro multipurpose X-ray diffractometer (employing monochromatic Cu-K radiation). Differential thermal measurements were carried out using a Mettler Toledo Differential Scanning Calorimeter (DSC) in the temperature range 100 0 C - 550 0 C at a heating rate of 10 0 C per min. Density of the bubble-free glass samples were measured by employing Archimedes principle using Toluene as an immersion liquid. The refractive index of the samples was measured by using Abbe refractometer by using a sodium vapor lamp at wavelength of 589.3 nm. Room temperature UV- Visible absorbance spectra in the wavelength range 300- 1000 nm of polished samples were recorded using spectrophotometer.
been synthesized by the conventional melt quench technique. The powder X-Ray diffraction analysis of the prepared samples confirms the amorphous nature of the samples. Density measurements for these glasses were done and physical parameters were studied. Structural properties of these glasses were analyzed through infrared spectra that were recorded between 1600cm -1 and 400cm -1 in transmission mode. The optical band gap for the glasses was obtained from plots between ℎ𝜈 against (𝛼ℎ𝜈) 2 and(𝛼ℎ𝜈)