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The PbGa 2 Se 4 crystal is a promising material for optoelectronic applications. It is caused by coexistence of the large polarized Pb cations and a huge contribution of anharmonic phonon subsystem caused by chalcogenide anions. In the present work the electronic and optical properties of the mentioned material were studied theoretically as well as experimentally by optical and X-ray photoelectron spectroscopy methods. The DFT approach has been used for the quantum chemical electronic properties calculations. Urbach rule and steepness parameters of the PbGa 2 Se 4 crystal have been evaluated for the first time. These parameters and Urbach energies increase with increasing temperature of the samples that is typical for the semiconducting materials. The XPS measurements of the investigated crystal reveal that all the spectral features are originated from core-level states of the constituent elements. Simultaneously these results also confirm non-reactivity of the PbGa 2 Se 4 surface. However, the titled single crystal possesses a number of intrinsic structural defects and vacancies thereby affecting its electronic properties. The electronic properties of PbGa 2 Se 4 are also affected by the existence of a strong electron–phonon interaction due to chalcogenide anions causing the decrease of an energy gap with temperature increasing. [ABSTRACT FROM AUTHOR]

Highlights: [•] Photoinduced enhancement of critical temperature in MgB2–Cr2O3 films was found. [•] Crucail role of electron–phonon interacton was shown. [•] Optimal ratio fundamental/SHG intensities was varied within 4:1 and 6:1. [Copyright &y& Elsevier]

Highlights: [•] Principal role of Au NP surface aggregation on the output photoinduced birefringence is shown. [•] The higher changes are obtained for the samples with sizes 30nm. [•] The process is slowly relaxed. [Copyright &y& Elsevier]

Abstract: The influence of crystallochemical affinity for crystals ZrGa2 and ZrGa3 on the optical properties was studied. We have calculated dispersion of optical constants . We have established that application of different exchange correlation potentials XC has no significant effect on the optical constant dispersion. Moreover, use of LDA, GGA and EVGGA has an insignificant effect on the corresponding optical features. The crystallochemical transformation between the two titled compounds leads to a spectral shift of the whole structure: for ZrGa3 it leads to higher energy shift with respect to ZrGa2. Moreover, one can see that the first spectral peak of for ZrGa2 which situated at around 0.5eV becomes very small for ZrGa3 but still situated in the same location. The first right hand side hump in – ZrGa2 which is located at around 1.5eV becomes pronounced and situated at around 2.2eV in – ZrGa3. For more complete information we have calculated dispersions of the electronic loss function, reflectivity and the optical conductivity. [Copyright &y& Elsevier]

Abstract: The glasses of the composition Li2O–ZrO2–SiO2: Pr2O3/Er2O3 mixed with three interesting sesquioxides (viz., Al2O3, Sc2O3, Y2O3) were synthesized. Optical absorption and fluorescence spectra (in the spectral range 350–2100nm were studied at ambient temperature. The Judd–Ofelt theory was applied to characterize the absorption and luminescence spectra of Pr3+ and Er3+ ions in these glasses. Following the luminescence spectra, various radiative properties like transition probability A, branching ratio β and the radiative life time τ for different emission levels of two rare earth ions have been evaluated. The radiative life times for the upper levels 3P0 (Pr3+) and 4S3/2 (Er3+) have also been measured and quantum efficiencies were estimated. The variations observed in these parameters were discussed in the light of changing environment of rare earth ions due to mixing of different sesquioxides in the glass network. [Copyright &y& Elsevier]

Abstract: An all electron full potential linearized augmented plane wave method, within a framework of GGA (EV-GGA) approach, has been used for an ab initio theoretical study of the effect of increasing tellurium content on the band structure, density of states, and the spectral features of the linear and nonlinear optical susceptibilities of the cadmium–selenide–telluride ternary alloys CdSe1−x Te x (x =0.0, 0.25, 0.5, 0.75 and 1.0). Our calculations show that increasing Te content leads to a decrease in the energy band gap. We find that the band gaps are 0.95 (1.76), 0.89 (1.65), 0.83 (1.56), 0.79 (1.44) and 0.76 (1.31)eV for x =0.0, 0.25, 0.5, 0.75 and 1.0 in the cubic structure. As these alloys are known to have a wurtzite structure for x less than 0.25, the energy gaps are 0.8 (1.6)eV and 0.7 (1.55)eV for the wurtzite structure (x =0.0, 0.25) for the GGA (EV-GGA) exchange correlation potentials. This reduction in the energy gaps enhances the functionality of the CdSe1−x Te x alloys, at least for these concentrations, leading to an increase in the effective second-order susceptibility coefficients from 16.75pm/V (CdSe) to 18.85pm/V (CdSe0.75Te0.25), 27.23pm/V (CdSe0.5Te0.5), 32.25pm/V (CdSe0.25Te0.75), and 37.70pm/V (CdTe) for the cubic structure and from 12.65pm/V (CdSe) to 21.11pm/V (CdSe0.75Te0.25) in the wurtzite structure. We find a nonlinear relationship between the absorption/emission energies and composition, and a significant enhancement of the electronic properties as a function of tellurium concentration. This variation will help in designing better second-order susceptibility materials by manipulating of the electronic structures of these materials with different compositions to achieve more delocalized atomic bonds. [Copyright &y& Elsevier]

Abstract: The glasses of the composition (45−x)ZnF2–xWO3–49TeO2:1.0Nd2O3/Sm2O3/Eu2O3 with x varying from 5 to 20mol% were synthesized. Optical absorption, fluorescence spectra (in the spectral range 400–2300nm) and also fluorescence decay were studied at ambient temperature. The Judd–Ofelt theory analysis was applied to characterize the absorption and luminescence spectra of Ln3+ ions in these glasses. Following the luminescence spectra, various radiative properties like transition probability A, branching ratio β and the radiative life time τ for 4F3/2 → 4I11/2, 4G5/2 → 6H7/2, 5D0 → 7F2 emission levels respectively for Nd3+, Sm3+ and Eu3+ doped glasses of these glasses have been evaluated. The variations observed in these parameters were discussed following of varying co-ordinations (tetrahedral and octahedral positions) and the valence states of tungsten ions in the glass network. A significant enhancement in the intensities of 4F3/2 → 4I11/2 (Nd3+), 4G5/2 → 6H7/2 (Sm3+) and 5D0 → 7F2 (Eu3+) emission lines has been observed with increase of WO3 content; this is attributed to the increase in the concentration W5+ ions in the glass network that acts as modifiers. The quantitative analysis of these results (with the aid of the data on ESR, IR and Raman spectral studies) has indicated that the glasses mixed with around 15mol% of WO3 have the optimum concentration for yielding the highest quantum efficiency with low phonon losses for the above-mentioned principal transitions. [Copyright &y& Elsevier]

Abstract: PbO–Sb2O3–B2O3 glasses mixed with different content of Pr2O3 (ranging from 0 to 0.6mol%) were crystallized. The samples were characterized by X-ray diffraction, transmission electron microscopy (TEM) and differential scanning calorimetric (DSC) techniques. The TEM studies indicated that the samples contain well defined and randomly distributed nanoclusters possessing the sizes within ∼30–40nm. The XRD spectra have exhibited diffraction peaks due to presence of Pb5Sb2O8, Pb3(SbO4)2, PbB4O7, β-PrSbO4, Pr3SbO7, Pr3Sb5O12 crystalline phases. From these spectra, it was identified that the antimony ions co-exist in Sb5+ state with Sb3+ state in the titled glass ceramic samples. The photo-induced birefringence (changes in refractive indices) caused by simultaneous exposure of the sample with the doubled frequency coherent laser beam (1.54μm and 0.77μm) was monitored by polarized probing beam of varying wavelength in the range of 750–1250nm. The induced birefringence exhibited a maximum at about 1000nm, a wavelength corresponding to 3H4 → 1G4 optical excitation transition of Pr3+ ion. We have established a correlation between the intensity of this transition and the birefringence dispersion. Principal role of the photo-occupation of this transition is identified. The variations of photo-induced birefringence with increase in the content of Pr2O3 is explained due to the increasing degree of disorder and increasing concentration of deformed PrO8 structural units in the glass ceramic. Further analysis of these results coupled with the data on IR and Raman spectral studies, has indicated that PbO–Sb2O3–B2O3 glasses crystallized with 0.6mol% of Pr2O3 exhibit maximal birefringence effects. [Copyright &y& Elsevier]

Abstract: PbO–Sb2O3–B2O3 glasses mixed with different concentrations of TiO2 (ranging from 0 to 1.5mol.%) were synthesized. The samples are characterized by X-ray diffraction, scanning electron microscopy and DSC techniques. A variety of properties, i.e. optical absorption, photoluminescence, infrared, ESR spectra, magnetic susceptibility, photo-induced birefringence (PIB) and dielectric properties (constant ɛ′, loss tan δ, a.c. conductivity σ ac over a wide range of frequency and temperature) of these glass–ceramics have been explored. The analysis of these results indicated that Ti ion surrounding ligands play principal role in the observed PIB and the sample crystallized with 0.8mol.% of TiO2 is the most suitable for the applications in non-linear optical devices. [Copyright &y& Elsevier]

Abstract: We present results of the band structure and density of states (DOS) for BaBiBO4 nonlinear optical single crystals, using full potential linear augmented plane wave (FP-LAPW) method. We have for the first time, performed the experimental investigations of the electronic density of the states. We have found that this crystal is a semiconductor with an indirect energy band gap. Theoretical results of the DOS spectra are in good accord with the X-ray photoelectron spectroscopy measurements with respect to peak positioning. The band structure can be thought as arising from a superposition of the BO3 and BiO5 clusters possessing substantially different ionicities. [Copyright &y& Elsevier]

Article reports design and synthesis, technology, crystal structure determination and results of photoinduced nonlinear optical investigations of novel TlInGe 2 S 6 crystals. We have discovered TlInGe 2 S 6 as a new type of laser induced nonlinear optical materials. Following the performed measurements we can use the titled crystals for laser operated coherent wavelength transformations. It was shown, that thin, photoinduced nanolayers formed by laser energies above the energy gap as well a near the phonon resonances possess promising nonlinear optical properties. Different types of cw lasers with the same powers of the photoinduced beams were used: SHG of the Nd:YAG laser (532 nm), fundamental Nd:YAG laser (1064 nm), and IR CO 2 laser with wavelength of 9400 nm. The crystal structure of novel quaternary thallium indium germanium sulphide TlInGe 2 S 6 determined by X-ray powder method possesses trigonal space group R 3. The as-derived TlInGe 2 S 6 crystalline alloy was probed employing the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) methods. Particularly, for the TlInGe 2 S 6 alloy surface, both pristine and 3.0 keV Ar + ion-irradiated, we have monitored the XPS valence-band and core-level spectra. These measurements indicate that the TlInGe 2 S 6 surface is rather stable with respect to Ar + ion-irradiation, which does not induce significantly near the surface layers sub-stoichiometry. Matching on a common energy scale of the XPS valence-band spectrum and the XES S Kβ 1,3 and Ge Kβ 2 bands indicates that main contributions of the S 3p and Ge 4p states are located in the upper and central portions of the valence band of TlInGe 2 S 6 , respectively, with significant contributions of these states in other valence-band parts as well. [ABSTRACT FROM AUTHOR]

Single crystals (Ga 55 In 45 ) 2 S 300 and (Ga 54.59 In 44.66 Er 0.75 ) 2 S 300 possessing space group P6 1 were successfully grown and explored with respect to laser induced piezooptics. Their structural properties were studied by Raman spectroscopy and additionally, dependence of different gamma ray doses on the photoinduced piezo-optical responses were also explored. Structural parameters were evaluated using the Rietveld methods following the X-ray diffraction data. The chemical composition of the synthesized samples was determined by EDS analysis. We discussed the influence of Er 3+ -doping on the crystal structure and piezo-optical properties. It was established that these crystals behavior is very sensitive to γ−irradiation dose and therefore they are promising for applications as elastooptical radiation sensors. [ABSTRACT FROM AUTHOR]

Highlights: [•] New type of optically operated rare earth doped borates is proposed. [•] Principal role of the pho9non subsystem in photoinduced electrooptics, SHG and piezooptics is shown. [•] The possibility to create the laser operated materials is shown for the such kind of sold state alloys. [ABSTRACT FROM AUTHOR]

Abstract: New composite membranes consisting of phosphosilicate (P2O5–SiO2) content and 1-ethyl-3 methylimidazolium tetrafluoroborate [EMIMBF4] ionic liquid were fabricated by sol–gel process. For all the prepared hybrid membranes, the interaction between the doped “hydrophilic” [EMIMBF4] ionic liquid and the inorganic phosphosilicate network was investigated by Fourier transform infrared spectroscopy. Average pore sizes and specific surface areas were investigated by the Brunauer–Emmett–Teller (BET) method. Thermogravimetry (TG) and differential thermal analysis (DTA) measurements confirmed that the hybrid membranes were thermally stable up to 220°C. Relatively a high conductivity of 1×10−2 S/cm (8.9×10−3 S/cm for 40wt% IL doped 60TMOS–30VTMOS–10PO(OCH3)3 (mol%) hybrid membrane) was obtained for 40wt% IL doped 30TMOS–30TEOS–30MTEOS–10PO(OCH3)3 hybrid membrane, at 155°C under anhydrous conditions. The hydrogen permeability was found to decrease within the range 10−11 to 10−12 mol/cmsPa for 40wt% IL doped membranes as the temperature increases from 20 to 150°C. [ABSTRACT FROM AUTHOR]

Abstract: PbO–Sb2O3–B2O3 glasses doped with different concentrations of Yb2O3 ranging from 0.2 to 0.6 (in mol%) have been synthesized and subsequently crystallized. The samples were characterized by X-ray diffraction, SEM and DSC techniques. The optical absorption and luminescence spectra have exhibited bands due to 2F7/2 → 2F5/2 and 2F5/2 → 2F7/2 transitions, respectively. Partial spectral overlap between emission and absorption bands has been observed. From these spectra, the absorption and emission cross-sections and fluorescence lifetime of Yb3+ ions has been evaluated. Following the obtained data, it was established that there is a less radiative trapping and enhanced fluorescence lifetime of Yb3+ ions in the glass ceramic samples with respect to those of amorphous samples. The reasons for such variations have been discussed in the light of variations in the oxidation states of antimony ions and changes in the structural units in the vicinity of Yb3+ ions in the glass network. [Copyright &y& Elsevier]

Abstract: We report theoretical calculation of the linear and nonlinear optical susceptibilities based on one of the most accurate methods for the computation of the linear and nonlinear optical susceptibilities of solids within density functional theory (DFT). The linear optical properties show negative uniaxial anisotropy indicating the strong anisotropy. Our calculations show that these crystals possess negative birefringence. The negative uniaxial anisotropy and birefringence will be in the favor of our calculated . These crystals possess very high first-order in the infrared spectral region. [Copyright &y& Elsevier]

Abstract: Density of electron states (DOS) measured by X-ray photoelectron spectra (XPS) on single crystals of a ternary oxyborate Na3La9O3(BO3)8 (NLBO) are reported for the first time. The Na3La9O3(BO3)8 ternary oxyborate nonlinear single crystals were synthesized by spontaneous crystallization on a iridium cylinder put in melts consisting of binary oxides. The novelty of the present work is that it describes the complete experimental picture of the total density of states (TDOS) for the valence band obtained by means of X-ray photoelectron spectroscopy. We compare the DOS obtained by XPS with band structure calculation. The latter was performed within the density functional theory, using a full-potential linear augmented plane wave (FP-LAPW) method. The valence band maximum (VBM) and the conduction band minimum (CBM) are located at Γ point of the Brilluoin zone resulting in a direct energy band gap of about 4.44eV comparing with our measured energy band gap (5.22eV). The VBM originates from O-p states, while the CBM is dominated by localized La-f states. We notice a different degree of hybridization between La-s, Na-s/p and O-s/p states in the valence and conduction bands. B-s is strongly hybridized with O-s states and B-p with O-p states in the VB at around −5eV. O-p states are weakly hybridized with La-s, Na-s/p at the VBM. [Copyright &y& Elsevier]

Abstract: A complex spectroscopic study of Ca4GdO(BO3)3 (GdCOB) doped with Pr3+ has been performed experimentally and theoretically using the ab initio configuration interaction (CI) calculation method. This approach is based on the numerical discrete-variational Dirac-Slater cluster calculations and numerical solution of the Dirac equation using the local density approximation. All relativistic effects are considered automatically by virtue of the relativistic Hamiltonian. The principal novelty of the approach is that during the calculations the molecular orbitals (MO) consisting of the atomic wave functions of the central ion (in this case, Pr3+) and its nearest ligands (O2−) are used. The principal advantage of the method consists in ab initio approach not requiring the fitting parameters like in the widely used crystal field approach or FLAPW requiring the muffin tin orbitals. Such a complete basis set allows not only to evaluate the main energy terms, but also to analyze the covalent charge transfer effects and to evaluate the energy separations between different MO groups. Using the GdCOB:Pr single crystals as good probes to check the introduced theoretical model, we report the calculations of the complete energy terms (including unoccupied excited MO) for the principal [PrO6]9− cluster. Theoretical simulations are verified by comparison with both the ground and excited state absorption. A particular interest presents estimations of the crystal field splitting of the localized Pr3+ 5d orbitals (10 Dq) (about 20,800cm−1) and energy separations between the 2p (O2−)–4f (Pr3+), 2p (O2−)–5d (Pr3+), and 2p (O2−)–6s (Pr3+) MO (13,300, 40,050, and 78,900cm−1, respectively). These values are in sufficient agreement with performed excited state absorption experimental data and available ground state absorption data including the low temperatures study at 4.2K. Several discrepancies between the calculated and measured intensities of the optical transitions can be explained by contribution of electron–phonon coupling and sample''s imperfections. In addition to the first principles calculations, crystal field theory was used to calculate the Pr3+ energy levels; a set of crystal field parameters for Pr3+ ion in GdCOB crystal is suggested. [Copyright &y& Elsevier]

A possibility to operate piezoelectric efficiency of δ-BIBO:Nd crystals using external nanosecond laser light at 1064 nm and 532 nm was shown. Depending on the kind of the photoexciting light the behavior of the output piezoelectricity was quite different. The measurements of temperature and temporary features for the photoinduced piezoelectricity confirmed the main role of the incorporation of Nd ions in the δ-BiB 3 O 6 structure with respect to piezoelectricity. The DFT simulations of the local charge density re-distribution were done using the norm-conserving pseudopotential method to confirm principal role of the space charge density redistribution. [ABSTRACT FROM AUTHOR]

Abstract For the Quaternary Chalcogenides BaCu 2 GeQ 4 (Q = S, Se) optoelectronic, structural and transport properties are explored using accurate all electrons FP–LAPW [full potential linearized augmented plane wave] method. The lattice constants calculated theoretically are established to be in fine agreement with the values that are measured experimentally. It is established that all the titled compounds are direct band gap semiconductors and this energy band gap is situated Γ- Γ symmetry points. At the same time the band gap magnitude decreases during replacement of S by Se. Optical constant dispersion like imaginary and real components of dielectric functions, extinction coefficients, refractive indices, reflectivity's, absorption coefficients, have been also calculated for these compounds. High absorption and the direct band gap characteristics of these compounds in the UV–Visible energy range indicate that these perovskite structures might be used in optoelectronic and optical devices working in the UV–Visible range of the energy spectrum. The calculated birefringence (−0.012 and −0.083) enhances the suitability of BaCu 2 GeSe 4 compared to BaCu 2 GeS 4 usually applied as nonlinear optical materials. The computed transport coefficients exhibit the anisotropic nature of the materials, in agreement with their electronic states. The transport properties show stronger carrier concentrations along the Ge-s, Ba-p and Cu-d orbitals, confirming that these orbitals are principal for the electrical transport features. The values of effective mass of electrons are computed by curvature of the CBM band 124 and 184 for BaCu 2 GeS 4 and BaCu 2 GeSe 4 respectively. Investigating of the thermoelectric power factor shows that BaCu 2 GeS 4 is much better than BaCu 2 GeSe 4 over the entire temperature interval which make it suitable for future technological applications. Graphical abstract Image 1 Highlights • Thermoelectricity of BaCu 2 GeQ 4 (Q = S and Se) compounds is explored. • The energy band gaps are of direct type with the extrema situated at R BZ points. • Plasmon resonances are observed in UV spectral range (6–12 eV). • Thermal conductivity of BaCu 2 GeSe 4 is lower than BaCu 2 GeS 4. [ABSTRACT FROM AUTHOR]

Abstract Using first principles density functional theory (DFT) simulations, the structural, electronic, optical and elastic properties of CaTa 2 O 6 oxide for cubic and orthorhombic phases are studied by highly accurate (FP-LAPW) method within the GGA + U approximation. The calculated lattice parameters are consistent with available experimental data. The electronic band structure calculations have shown that the band gaps in CaTa 2 O 6 are equal to 3.08 eV and 4.40 eV for the cubic and orthorhombic structures, respectively. For both the phases the main optical properties, e.g., absorption coefficient, dielectric constant, energy loss function, reflectivity are calculated and discussed in detail in the spectral range 0–14 eV. Cubic and orthorhombic phases exhibit significantly different optical characteristics. The electronic bonding characters of CaTa 2 O 6 with different symmetries are explored via charge density distribution mapping. Strong covalent bonding character dominates in both the phases of CaTa 2 O 6. Elastic properties of CaTa 2 O 6 for cubic and orthorhombic phases are also investigated. The stress strain method is used for the determination of elastic constants in both the phases. The bulk modulus, shear modulus, Young's modulus, along with the important elastic anisotropy factors and Poisson's ratio are studied in detail. Graphical abstract Image 1 Highlights • Electronic, and optical properties of CaTa 2 O 6 in cubic and orthorhombic phases are studied. • Energy band gaps were equl to 3.08 and 4.40 eV, respectively. • Optoelectronic features are due to Ca-s, Ta-p, O-p orbitals in (c.p.), Ta-p and O-(o.p.) • The Zener factor and Poison's ratio confirm elastically anisotropic characteristics. [ABSTRACT FROM AUTHOR]

Abstract Nitrido silicates are emerged as highly efficient luminescent materials (phosphors) that found considerable industrial application as white light emitting diodes (LEDs) have been studied with respect to band structure and related electronic structure parameters. They have tunable optical properties, as the band gap is of indispensable because it determines both the electrical and optical features of the material, which can be varied by the material composition (by doping technique). It is found also that the nitride (alumo) silicates "Sr 2 Si 5 N 8 : Eu2+" have wide industrial application as highly efficient red-emitting phosphor materials in pc-LEDs. In this report we apply density functional theory (DFT) within the GGA+U approach to study the structural, electronic and optical properties of Eu2+ and Ce3+ doped Sr 2 Si 5 N 8. The total energy has been optimized as a function of the unit cell volume. Electronic structure including, the electronic density of state (DOS), the band structure and the linear optical susceptibility are calculated for the relaxed structure applying the optimized lattice constant. The calculated optical dispersion of dielectric susceptibility are closely related to the corresponding electronic structure and our results are in very good agreement with experimental data. Graphical abstract Image 1 Highlights • Complex studies of band structure for Sr 2 Si 5 N 8 and doped compound with Eu2+and Ce+3 have been done. • Static value of real part for pure Sr 2 Si 5 N 8 is 2.1 while for Eu2+ doped Ce+3 2.6–2.9 • Plasmonic resonances appear at 12.5 eV and for doped – at 10.5 eV. • Main perspectives of eh further improvements of the optical constants are given. [ABSTRACT FROM AUTHOR]

Abstract In the present work, we investigate, in detail, the phase diagrams of the TlGaSe 2 –Zn(Cd,Hg)Se systems, which are quasi-binary and eutectic type. The solid phase solubility on the basis of components did not exceed 5 mol% at 670 K. The crystals of TlGaSe 2 : Zn+2(Cd+2, Hg+2)) solid solutions were prepared by Bridgman-Stokbarger method. It was established that the doping of Zn+2, Cd+2, Hg+2 leads to a slight decrease in the values of both the direct and indirect band gap energies with respect to the that in undoped TlGaSe 2 crystal. The temperature dependence of the band gap values for all the synthesized compounds is crucial for semiconductor applications. Also, the dominant mechanisms are proposed that contribute to the fundamental absorption edge tailing. Graphical abstract Image 1 Highlights • High quality TlGaSe 2 crystals, doped by Zn+2 or Cd+2 or Hg+2 crystals has been successfully growth for first time. • Single crystals were grown using a horizontal version of Bridgman -Stokbarger method. • Doping decrease of both the direct and indirect band gap energy with respect to the undoped TlGaSe 2 crystal. • Phase diagrams of the TlGaSe 2 –Zn(Cd)Se systems were investigated by DTA, XRD and microstructure analysis. [ABSTRACT FROM AUTHOR]

Abstract Optical and magnetic features of the A 2 V 2 O 2 (A = F e and C o) compounds are explored. Density functional theory (DFT) within a framework of FPLAPW (full-potential linearized augmented plane wave) method, as well as generalized gradient approximation plus the Hubbard parameter (GGA+U) and Hubbard on-site Coulomb interaction corrections are applied. U is evaluated assuming constraint generalized gradient approximation for transition metals Fe/Co and V. The calculated band structures for the Fe doped compounds demonstrate the metallic nature while for the Co doped we observe half metallicity possessing 100% spin polarization in the vicinity of the Fermi level. The influence of Fe/Co and V magnetic moment (μ B) on the electronic, magnetic and optical features is explored in details additionally. The optical constants reveal the strong response for A 2 V 2 O 2 (A = F e and C o) in the IR (infra-red region) and UV (Ultra Violet) regions. Graphical abstract Image 1 Highlights • A 2 V 2 O 7 (A = Fe and Co) band structure was studied by functional theory based on FP-LAPW. • The spin polarized structure is more stable as that of without spin structure. • From the Fermi surface Co 2 V 2 O 7 has higher electrical conductivity as compared to Fe 2 V 2 O 7. • Spin polarized magnetic moments is 19.356 μ B (Fe 2 V 2 O 7), 14.002 μ B (Co 2 V 2 O 7). [ABSTRACT FROM AUTHOR]

Recently Cu 3 SbSe 4 have attracted enhanced an interest due to abundant potential for extensive thermoelectric applications. To get a complete prediction of its thermoelectric performance and charge transport details it is important to have fundamental data concerning band structure. In the present work we have conducted comprehensive investigations of the electrical transport properties of Cu 3 SbSe 4 using first-principles DFT band structure calculations combined with the Boltzmann transport theory.The novel 0, 2, 4 and 6% strain Cu 3 SbSe 4 material within the frame of DFT (density functional theory) approach have been explored. First of all the electronic structure properties of the bulk material (LAO) are discussed and then the effects of different degree of strain on the electronic and thermoelectric properties are discussed.We have carried out full relaxation procedure of the atomic structure and found that a deviation by less than 1–5% from experimental data. The band structure dispersion and densityof states (total and partial) are presented. The thermoelectric properties (like Seebeck coefficient, electrical conductivity, thermal conductivity, power factor (PF) and Figure of Merit (ZT) have been discussed) versus temperature. The highest power factor obtained was equal to about 6.5∼7.0 × 10 11 W / m K 2 s at 850 K. This result suggests that p-type doping can enhance the thermoelectric properties of 0, 2, 4 and 6% strain Cu 3 SbSe 4 materials in the high temperature range. Our results demonstrates a reasonable agreements with the previous results and predict the great potential for enhancement of the thermoelectric performance of Cu 3 SbSe 4 . [ABSTRACT FROM AUTHOR]

New quaternary sulfide PbGa 2 GeS 6 crystal was synthesized from co-melting high-purity elements The studies of second harmonic generation and the third harmonic generation for new quaternary sulfide PbGa 2 GeS 6 crystal have shown that its nonlinear optical response is higher with respect to other similar compounds. The band structure analysis performed by X-ray spectroscopy methods and first principles DFT band structure calculations indicate that the main contributions of the S 3p states are located at the top of valence band, while those of the Ga 4p states give contribution to the central and upper portions of the valence band of the PbGa 2 GeS 6 compound. The calculations reveal that the band gap E g  = 2.445 eV is indirect and is formed between the valence Γ-point and the conduction X-point of Brillouin zone. The theoretically evaluated band gap energy is close to the experimental value, namely E g  = 2.37 eV at 300 K The present results allow recommending PbGa 2 GeS 6 for nonlinear optical application in the near IR spectral range. At the same time, the crystal possesses a good transparency in the mid-IR spectral range. [ABSTRACT FROM AUTHOR]

Magnesium and Copper co-doped Zinc oxide nanorods (ZnO NRs) were grown on glass substrates applying hydrothermal technique. They were investigated with respect to their structural and morphological insights through X-ray diffraction (XRD) patterns, field emission scanning electron microscope (FESEM) and atomic force microscope (AFM) technique. The nanorod diameters were found to vary within 105 nm–153 nm. The nanorods were hexagonal in shape with wurtzite structure and oriented along c -axis. Band gap magnitudes were evaluated from the UV–Visible absorption spectra and were found to be higher for Mg5%Cu2%ZnO nanorod sample owing to its smaller crystallite size. Photo-polarization did the additional alignment in the nanorod samples to observe optical nonlinearity of the first and second order. When the spectral energy of the laser beam matched with the energy of the absorption band edge of the samples, we observed also third harmonic generation (THG) besides second harmonic generation (SHG). Quantum chemical calculation using norm-conserving pseudo-potential method was applied to confirm the origin of the effects. [ABSTRACT FROM AUTHOR]

Comprehensive studies on piezo-optical (elasto optical) effects stimulated by bicolor coherent treatment using Er:glass laser, at λ = 1540 nm and its second harmonic generation (λ = 770 nm) insitu with mechanical stress, ultrasonic velocities and elastic coefficients of PbO−ZrO 2 −SiO 2 : TiO 2 glass ceramics were carried out as a function of concentration of crystallizing agent TiO 2 . The contribution to the piezo-optical effects is attributed to Pb 2 Ti 2 O 6 pyrochlore crystal phases appeared in the glasses during crystallization. The observed piezo-optical effects are attributed to simultaneous interference of the contributions due to the induced gratings (because of the bicolor treatment) and the piezo-optically originated birefringence. The variation of piezo optical coefficients, ultrasonic velocities and various elastic coefficients viz., Young's modulus, shear modulus, micro hardness etc., with the concentration of TiO 2 exhibited the maximal effect at 0.6 mol% content of TiO 2 . From the quantitative analysis these results together with the results of other studies ( viz., XRD, SEM, EPR, IR, optical absorption spectral studies), it is predicted that the PbO−ZrO 2 −SiO 2 glass crystallized with 0.6 mol% of TiO 2 is embedded with higher concentration of Pb 2 Ti 2 O 6 pyrochlore crystal phases (a crystal phase consisting of Ti 4+ ions) and such crystal phases are found to be responsible for observed maximal effects of all the mentioned properties for this sample. [ABSTRACT FROM AUTHOR]

This work reports the high-pressure and high-temperature (HP-HT) synthesis of pure monoclinic phase of GdNbO 4 :Bi 3+ phosphors. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence, and IR spectra were utilized to characterize the synthesized phosphors. The crystal structure distortions operated by the pressure leads to tunable emission varying from blue to yellow. A small increase of the probability of non-radiative energy transfer with increase of pressure is observed. It is shown that the efficiency of the energy transfer process is dependent on pressure. The calculations of CIE chromaticity coordinates were performed. [ABSTRACT FROM AUTHOR]

This study is mainly focused on electrical characteristics of PbO−ZrO 2 −SiO 2 : TiO 2 glass ceramics embedded with Pb 2 Ti 2 O 6 cubic pyrochlore crystal phases. The samples were synthesized by usual melt quenching technique and subsequent heat treating at crystallization temperature for prolonged times. The samples were characterized by XRD, SEM and DSC, IR, EPR and optical absorption spectroscopy techniques. Later, dielectric properties viz ., dielectric constant, loss tangent, electric moduli, electrical impedance and a.c. conductivity over wide ranges of frequency and temperature, have been measured as a function of TiO 2 content. The results of characterization techniques viz., XRD, SEM and DSC, indicated that the samples are embedded with multiple crystal grains (with sizes varying from 0.1 to 1 μm) cemented with residual glass phase. The volume fraction of the crystal grains is found to increase with increase of TiO 2 content. The XRD studies on PbO−ZrO 2 −SiO 2 :TiO 2 glass ceramics revealed that Pb 2 Ti 2 O 6 cubic pyrochlore crystal phase is the principal phase present in the bulk samples. The studies have also confirmed that a small part of Pb(Zr 0.5 Ti 0.5 )O 3 and Ti 2 O 3 crystal grains are also present in the titled glass ceramics. The results of IR spectral studies have indicated that there is an increasing degree of polymerization of glass network with increasing TiO 2 content up to 0.6 mol%. This is attributed to the presence of Ti ions predominantly in Ti 4+ state (in this concentration range of TiO 2 ) that take part in the network forming positions with TiO 4 and also substitutionally positioned octahedral sites. The results of optical absorption and EPR spectral studies have pointed out that a part of the Ti ions were reduced to Ti 3+ state and such ions were predicted to act as modifiers. These studies have also indicated that the concentration of Ti 3+ ions is higher in the samples crystallized with 0.8 and 1.0 mol%. The values of dielectric parameters are decreased with increasing of crystallizing agent. The decrease is attributed to the participation of Ti ions in the formation of Pb 2 Ti 2 O 6 cubic pyrochlore crystalline phases with TiO 4 structural units. Quantitative analysis of the dielectric properties of PbO−ZrO 2 −SiO 2 :TiO 2 glass ceramics together with the results of spectroscopic studies indicated that the electrical insulating strength is the highest for the glass crystallized with 0.6 mol% of TiO 2 . [ABSTRACT FROM AUTHOR]

In the present work, details of the crystal growth (Bridgeman method) and optical reflection spectroscopy for two single crystals (X = S, Te) were reported. Detailed ab-initio DFT calculations of the structural, electronic and optical properties of the crystals were performed for a deeper understanding of the experimentally obtained optical data. The special attention is paid to the electron charge density distribution, carrier mobility, optical reflectivity spectra and finally the anisotropy of the corresponding optical functions were studied. Were established a relations with carrier mobility, the optical anisotropy and electronic band structures for the titled crystals and compared with the optical reflectance spectra, covering the range of principal inter-band transitions. The origin of the calculated bands and effects of the anion substitution (Se by Te) on the crystal properties are studied. The role of screening effects is discussed by a comparison of the GGA and LDA approaches, including the electronic band dispersion and effective masses anisotropy. The possible changes of the inter-band transition are considered. The relation between the space charge density distribution and optical features is established. Finally was explained the origin of the observed discrepancies between the experimental and theoretical data. [ABSTRACT FROM AUTHOR]

Six optically transparent zinc molybdenum borotellurite glasses containing different network modifier ions (alkali, alkaline, and heavy metal oxides) with compositions, 60TeO 2 –10B 2 O 3 –10MoO 3 –10ZnO–10M (mol%) (M = Li 2 O, Na 2 O, K 2 O, MgO, CaO, and PbO) were prepared by melt quenching technique. For all these glass matrices, physical, structural, thermal, and optical properties have been studied. The physical properties of all the glasses were evaluated with respect to the glass composition. The structure of the glasses was monitored by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray analysis (EDAX), Attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and Raman spectroscopy. The XRD and SEM measurements reveal the amorphous nature for all the prepared glasses and EDAX confirms that all the elements present in the respective glasses. The presence of various functional groups such as stretching vibrations of the TeO 4 trigonal bi-pyramid structure, asymmetrical stretching vibrations of the TeO 3 trigonal structural units, B–O bond stretching in BO 4 groups, asymmetric stretching vibrations of B––O bond in trigonal BO 3 units from various types of borate groups, stretching vibrations of Mo–O–Mo linkages, corner shared MoO 6 octahedra units, stretching vibrations of Mo–O − bonds in MoO 6 units, including stretching vibrations of ZnO 4 − structural units, and non-hygroscopic nature of the glasses are confirmed by ATR-FTIR and Raman spectra, respectively. It is established that the glass network is primarily a mixture of TeO 4 , TeO 3 /TeO 3+1 and BO 4 , BO 3 structural units. The thermal properties of the glasses were obtained by performing simultaneous thermal analysis (STA). For these glasses, from the differential scanning calorimetry (DSC) profiles the glass transition temperature (T g ), onset crystallization temperature (T x ), crystallization temperature (T c ), and melting temperature (T m ) are identified and from these values, all relevant thermal parameters were evaluated to obtain complete thermal behavior of the synthesized glasses. The calculated thermal stability values have been varied in the temperature range of 106–189 °C with different modifier ions incorporation. For alkali metal oxides incorporated glasses reduced glass transition temperature (T rg ) values almost coincide with classical two-third rule while alkaline and heavy metal oxides based glasses weakly obey this rule in our study of relationship between glass transition temperature (T g ) and melting temperature (T m ). From the measured optical absorption spectra of all the glasses, direct and indirect optical band gap energies were evaluated and the values of indirect optical band gap energies calculated from absorption spectra ( E opt ) match well with the values of optical band gap energies ( E o p t a s f ) calculated from absorption spectrum fitting (ASF) method. The optical absorption cut-off wavelengths have shown a gradual spectral red shift from Li to Pb oxides based glass compositions indicating the decrease of rigidity of the glasses. Optical band gap energies were calculated to be within the range of 2.325–2.655 eV for direct and 1.790–2.378 eV for indirect transitions and both direct and indirect band gap values decreases monotonically from Li to Pb oxides introduced glass. The structural, thermal, and optical features of all the synthesized tellurite rich glasses with different modifier ions are understood and our comprehensive analysis could contribute towards the development of suitable fiber Raman amplifiers. [ABSTRACT FROM AUTHOR]

Tuning the structural, thermal, and optical properties of low phonon energy glasses such as tellurite glasses (phonon energy ∼750 cm −1 ) with suitable rare earth dopants is a key issue in the fabrication of solid state lasers and optical amplifiers. In this work, (70-x) TeO 2 -10 WO 3 -10 ZnO-5 TiO 2 -5 Na 2 O-(x) Pr 2 O 3 (x = 1.0–5.0 mol %) glasses were synthesized with high optical quality and characterized using X-ray diffraction (XRD), Scanning electron microscopy and Energy dispersive X-ray analysis (SEM-EDAX), Attenuated total reflectance-Fourier transform infrared (ATR-FTIR), Raman spectroscopy, Thermo-gravimetric analysis (TGA), Differential scanning calorimetry (DSC), optical absorption and luminescence techniques. The XRD and SEM measurements reveal the amorphous nature of all the prepared glasses and EDAX confirms all the elements present in the respective glasses. The presence of various functional groups such as stretching vibrations of Te–O bonds in the [TeO 4 ] trigonal bi-pyramid units, symmetrical stretching or bending vibrations of Te–O–Te or O–Te–O linkages at corner sharing sites along the chains of TeO 4 , TeO 3 and TeO 3+1 , stretching vibrations of W–O – and W O bonds in WO 4 tetragonal or WO 6 octagonal units, vibrations of Zn–O bonds from ZnO 4 groups, including non-hygroscopic nature of the glasses are confirmed by ATR-FTIR and Raman spectra, respectively. For Pr 3+ -doped glasses, from the DSC profiles the glass transition temperature (T g ), onset crystallization temperature (T x ), crystallization temperature (T c ), and melting temperature (T m ) are identified and the evaluated thermal stability values varied in the temperature range of 169–220 °C with increasing Pr 3+ doping concentration. Further, the Pr 3+ -doped tellurite glasses demonstrate excellent glass stability with higher criterion of Hruby’s value (H R ) between 1.9 and 3.9. From the measured optical absorption spectrum, experimental oscillator strengths are calculated and used to evaluate three phenomenological Judd-Ofelt (J-O) intensity parameters Ω λ ( λ = 2, 4 and 6) and respective radiative properties such as radiative transition probabilities (A R ), the branching ratios (β R ), and the radiative lifetime (τ R ) of metastable states for 1.0 mol % Pr 3+ -doped glass. Five main emission transitions at 3 P 0 → 3 H 5 (530 nm; green) with a shoulder at 543 nm, a weak band at 1 D 2 → 3 H 4 (592 nm; orange), 3 P 0 → 3 H 6 (615 nm; orange), 3 P 0 → 3 F 2 (649 nm; red), and 3 P 0 → 3 F 3 (686 nm; red) upon exciting at 486 nm ( 3 H 4 → 3 P 0 ) wavelength are observed from the luminescence spectra of Pr 3+ -doped tellurite glasses. Following the energy level diagram, Pr 3+ ion concentration quenching on the luminescence intensity has been explained by a non-radiative energy transfer between the ions through cross-relaxation and energy migration processes. The concentration dependent structural, thermal, and optical behaviors of Pr 3+ -doped tellurite glasses are understood and our systematic analysis could contribute towards the development of suitable optical devices fabrication. [ABSTRACT FROM AUTHOR]

We have found substantial increase of the infrared third harmonic generation (THG) for the fundamental wavelength 9.4 μm of microsecond CO 2 laser for Bi 2 Fe 4 O 9 microcrystalline powders. Additional enhancement of the THG signal was achieved by use of Er:glass 20 ns laser generating at 1540 nm before the IR probing of the THG. At the same time the analogous effect for the photoinduced two-photon absorption (TPA) was substantially less. The observed effect is explained within a framework of phenomenological description. Principal role here is played by magneto-electric interactions due to interactions of ferroelectric polarizations and ferromagnetic states. The observed effect may be used for creation of IR laser magneto-optical materials. [ABSTRACT FROM AUTHOR]

Exploring better Gamma, X-Ray and IR-Mid-R detectors, adequately sensitive to ambient temperatures and environmental conditions, is highly desirable. Therefore, following this path, we present detecting opportunities, based on data of experimental and theoretical investigation of the electronic and optical properties, photocurrent behavior at different bias voltages as well as the reflection for the He-Cd cw laser after irradiation by three different IR laser wavelengths, for recently grown TlPb 2 BrI 4 single crystal with strong anisotropic, two-dimensional (2D) layered structure. The X-ray photoelectron spectroscopy brings data on binding energy values of core levels of TlPb 2 BrI 4 for both as-grown and Ar+-ion-treated crystal surfaces as well as for elucidation of the energy distribution of the valence electronic states. In opposite to well-known IR-detector materials, TlPb 2 BrI 4 crystal surface shows high chemical stability concerning Ar+-ion bombardment. Further, we carry out ab initio band-structure calculations to gain curves of total and partial densities of states and to elucidate the principal optical constants of TlPb 2 BrI 4. The present studies indicate that, in spite of the fact that the TlPb 2 BrI 4 crystal contains two very hazardous/toxic chemical elements, thallium and lead; however, it is chemically stable and reveals very low hygroscopic behavior when being exposed to environmental conditions. [Display omitted] • Measurements of the time-resolved photocurrent are performed for TlPb 2 BrI 4 crystal. • Explanation of conversion rate of TlPb 2 BrI 4 crystal in the framework of the layered 2D structure is made. • IR photoinduced changes in reflectivity geometry of TlPb 2 BrI 4 are explored. • Crystal structure of novel layered TlPb 2 BrI 4 compound is refined. • Electronic structure and optical properties of TlPb 2 BrI 4 crystal are studied in detail. [ABSTRACT FROM AUTHOR]

Novel AgGa 0.95 In 0.05 Ge 3 Se 8 single crystalline alloys were grown via Bridgman–Stockbarger route and characterized by XRD analysis. The titled compounds were used for laser stimulated piezoelectricity studies. Following the results of differential thermal method as well as XRD phase analysis the phase equilibrium diagrams of AgGaGe 3 Se 8 –AgInGeSe 4 and AgGaGe 3 Se 8 –‘AgInGe 3 Se 8 ’ sequences were built. The specific features of phase diagrams demonstrate the possible high sensitivity of the such kind of crystal to external light and mechanical fields. Piezoelectric coefficient of the crystal was found to be strongly sensitive to illumination with 532 nm cw laser light which led to up to 90% decrease of the piezoelectricity. Photo-thermal contribution to the observed drop in piezoelectric voltage was excluded. [ABSTRACT FROM AUTHOR]

Calcium doped zinc oxide nanorods on ZnO seed layers were grown by hydrothermal method. Photoinduced bicolour laser treatment was done on the samples and the effective second order nonlinear coefficient ( d eff ) has been measured. The morphology of the samples was investigated by the field emission scanning electron microscope (FESEM) images. The structural parameters acquired from X-ray diffraction (XRD) patterns have been correlated with the measured d eff . The results have revealed that 15 mol% Ca doped ZnO nanorod showed maximum d eff because of the Lorentz local field established along the length of the nanorod. The aspect ratio and stress play a significant role in enhancement of d eff . The nonlinearity has been correlated with the absorption cross sections. [ABSTRACT FROM AUTHOR]

An increase of second order nonlinear optical efficiency was established for Cr 3+ doped β-BaTeMo 2 O 9 (BTMO) nanocrystallites (with sizes varying within up to 150 nm range) under influence of two coherent beams of 532 nm nanosecond pulsed lasers at power densities up to 600 MW/cm 2 . It was found that maximal enhancement of optical second harmonic generation was achieved for BTMO:Cr 3+ nanocrystallites possessing sizes about 60–80 nm. Occurrence of some quasi-periodic space radial grating was observed as well. This is a consequence of competition between the photo-polarization and photo-thermal effects. Band structure simulations within a framework of the norm-conserving pseudopotential were performed. [ABSTRACT FROM AUTHOR]

Single crystals of three oxide compounds containing stoichiometric Nd, doped with Yb 3+ ions, namely K 5 Nd(MoO 4 ) 4 (KNM), RbNd(WO 4 ) 2 (RNW), and NdAl 3 (BO 3 ) 4 (NAB) were grown from melts using Czochralski method or top seeded solution growth technique. Nd 3+ fluorescence characteristics were measured in dependence of Yb 3+ content and temperature. It was established that increasing Yb 3+ content results in a decrease of the Nd 3+ lifetime. However, the corresponding decay times values were quite different and varied from 9.5 μs for NAB up to 60 μs for KNM and 3.3 μs in RNW. Judd–Ofelt theory was applied to estimate the intrinsic lifetime of the 4 F 3/2 emitting level of Nd 3+ for all three crystals. The calculated lifetime values are much higher than the measured values. This effect is attributed to the strong concentration quenching of the Nd 3+ ions due to their high concentration in all three crystals. The possible mechanisms of the observed dependences are given. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lanthanum-alumino-silicate gels with high fluorine content are synthesized. [•] Trifluoroacetic acid (TFA) is used as the fluorine source in a sol–gel process. [•] Thermal decomposition of TFA prevents the conversion of gels to monolithic glasses. [•] The Ce-doped gels show photoluminescence in the blue spectral region. [Copyright &y& Elsevier]

Highlights: [•] High-pressure Raman spectra of β-BaTeMo2O9 were measured. [•] Pressure dependence of phonon modes was established. [•] Two structural phase transitions were discovered at 3.1 and 7.0GPa. [•] Mechanisms of these transitions were explained. [ABSTRACT FROM AUTHOR]

Highlights: [•] Electronic band structure of pure and Yb-doped RbNd(WO4)2 crystals are obtained. [•] Ab initio calculations and spectroscopic ellipsometry measurements are used. [•] Dielectric function of the crystal in the range of 4–10eV is formed by WO4-groups. [•] Changes of dielectric function due to Yb doping and due to anisotropy are comparable. [ABSTRACT FROM AUTHOR]

Highlights: [•] Emission features of Dy3+ ion were studied as a function of Al2O3 concentration in lead silicate glasses. [•] The emission spectra exhibited bands due to 4F9/2 → 6H15/2(B),6H13/2 (Y), 6H11/2 and 6H9/2 transitions. [•] The Y/B integral intensity ratio is found to decrease with increase in the concentration of Al2O3. [•] The decrease Y/B ratio is explained interms of structural modifications in the vicinity of the Dy3+ ion. [Copyright &y& Elsevier]

Abstract: Praseodymium-doped BiB3O6 glass was synthesized and a wide range of its optical properties was studied, including absorption, excitation and high resolution time resolved luminescence spectra. Particular interest was devoted to study of their time decay kinetics of induced fluorescence under influence of the third harmonic Nd:YAG laser illumination (355nm). Role of borate glass matrices contributing through the electron–phonon interaction to the time-decay kinetics of fluorescence is discussed. Comparison with other glass matrices is performed both following the Judd–Ofelt analysis as well as experimental decay times for principal fluorescence lines. [Copyright &y& Elsevier]

Abstract: Hereby we present synthesis and spectral properties dysprosium-doped BiBO glass, namely Bi0.97Dy0.03B3O6. We have explored UV–vis absorption, photoluminescence (PL) emission and excitation spectra as well as luminescence decay kinetics using Jasco V-570 spectrophotometer to record absorption spectrum. For measurement of PL emission spectra we have used a pulsed (pulse energy ca. 1μJ, pulse duration 10ns) third harmonic generation of Nd:YAG laser operating at 355nm and 10kHz. The experimental studies were done in a backscattering geometry. Fluorescence decay kinetics was derived from integrated time-resolved resolved spectra. [Copyright &y& Elsevier]

Abstract: We present a complex fluorescence study of a series of gadolinium oxide polycrystalline powders singly, doubly and triply doped with trivalent rare earth ions (Er3+, Tb3+, and Dy3+), to explore a possibility of their use as materials for white light emitting diodes. The excitation and luminescence spectra along with the decay kinetics were measured in the temperature range from 6 to 300K. The luminescence efficiency was studied within the visible spectral range, i.e. −400nm to 750nm under excitation by 355nm third harmonic Nd:YAG laser pulses. Singly doped Er3+ sample gave stronger luminescence signals, but others showed significantly larger decay lifetimes. The successive rare earths doping leads to substantial changes of the spectral positions due to the up-conversion processes. In the singly (Er3+) doped sample, following the time resolved spectrum and decay curves, there are two different types of emissions: at 660nm and at shorter wavelengths (below 640nm) the red emission''s lifetime is ten times longer than at shorter wavelengths. The singly doped sample shows unclear temperature-dependence of luminescence with lifetime at 550nm (the longest at 100K, similarly at 6K and 300K) and achieved luminous efficacy 73.5lm/W. [Copyright &y& Elsevier]

Abstract: In this work, the effect of ITO substrate on Ag NP size, morphology and photoinduced absorption depending on the time of 30ps laser treatment were explicitly studied. Silver nanoparticles with an average diameter of ∼40nm supported on indium tin oxide (ITO) were irradiated with a tightly focused pulsed laser (doubled frequency beam) at 532nm. The size transformation of silver nanoparticles induced by a single pulse of Nd:YAG laser (λ =532nm, pulse width=30ps) was directly observed by an electron scanning microscopy (FE-SEM) on indium tin oxide surface. Simultaneously the change in the absorption and the corresponding derivatives are also presented. These morphological changes are accompanied by a significant change in the optical absorption properties of the array. This study demonstrates that picosecond laser irradiation is an excellent technique to operate and control the properties of nanostructured materials on solid supports. [Copyright &y& Elsevier]

Abstract: Nickel nanoparticles (Ni-NPs) were successfully synthesized and attached on indium tin oxide (ITO) substrate by two different methods: from solution reduction process by using sodium borohydride (NaBH4) as reducing agent in the presence of poly(N-vinilpyrrolidone) (PVP) as protective and stabilizing agents and by polyol process under ethylene glycol EG as a solvent. The results indicated that the samples prepared in aqueous solution show the occurrence of face-centered cubic metallic nickel nanoparticles with a medium diameter of ∼31nm and good size dispersion compared to the preparation in EG that revealed large size ∼150nm. The dynamics of the nanoparticle''s growth in the solvents and comparison with optical absorption is presented. [Copyright &y& Elsevier]

Abstract: The TlInSe2–SnSe2 quasibinary system was investigated using differential thermal and X-ray phase analysis methods. The phase diagram is of eutectic type (V type of the Rozeboom classification). The solid solution range of the ternary compound in the TlInSe2–SnSe2 system extends to 28mol.% SnSe2 at 670K. The eutectic point coordinates are 63mol.% SnSe2 and 788K. [ABSTRACT FROM AUTHOR]

Abstract: A new strategy derived from seed-mediated growth was applied to attach and grow dense and uniform silver nanoparticles (AgNPs) on indium tin oxide (ITO) thin films deposited on glass substrate. This approach allowed obtaining narrower nanoparticle''s size distribution and a much denser attachment compared with the classical seed-mediated growth method. Adjusting growth time permitted preparing relatively small and uniform Ag nanoparticles of less than 40nm in size. The size, density and the regularity of AgNPs were found to be slightly affected by the nature of ITO substrate, which thus affects the plasmon absorbance spectra. The observed differences are attributed to the cavities existing between large grains and sub-grains of ITO thin films. [Copyright &y& Elsevier]