D.M. Petrović

Refractive-index dispersion and the optical-absorption edge of wedge-shaped thin films of metal - chalcogenide glasses

The optical constants and average thickness of metal - chalcogenide glass films of chemical composition , with x = 5, 10 and 15 at.%, are very accurately determined by a novel method, based only on the transmission spectra at normal incidence, measured over the 400 - 2200 nm spectral range. This useful optical method takes into consideration the non-uniform thickness of the thermally evaporated films (if not corrected, this may lead to too-large calculated values of the absorption coefficient, as well as serious errors in the values of the refractive index and film thickness). The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple and DiDomenico model. The optical-absorption edges are described using the non-direct transition model proposed by Tauc and the optical energy gaps are calculated by Taucs extrapolation. It has been found that the value of the refractive index increases clearly with copper content, whereas the optical band gap decreases from 1.80 to 1.64 eV.

Nickel (II) and cobalt (II) complexes of the hydrazide of 1-naphthylacetic acid

SummaryThe hydrazide of 1-naphthylacetic acid forms both bis- and tris-(ligand) high-spin nickel(II) and cobalt(II) complexes possessing an octahedral configuration. The compositions of the complexes are influenced not only by the metal-ligand stoichiometry but also by the nature of the inorganic anion. A physico-chemical investigation showed that the ligand is neutral and bidentate, coordinated through amido-nitrogen and carbonyl oxygen. The compounds were characterized by elemental analysis, magnetic measurements, i.r. and diffuse-reflection spectra and molar conductivity.

Thermal stability and thermomechanical characteristics of Cu-As-S-Se glasses

Abstract Thermal analysis and X-ray powder diffraction at different temperatures were employed to characterize the thermal stability of the Cu–As–S–Se bulk glasses. Differential thermal analysis was employed to determine the temperature of softening and partial crystallization of samples. Thermal treatment of the samples to 1273 K and recording of the corresponding thermogravimetric and derivative thermogravimetric curves allowed elucidation of the overall mechanism of their decomposition. The method of high-temperature X-ray diffraction enabled identification of the crystalline form appearing in particular phases of thermal treatment of the materials. The coefficients of linear thermal expansion in solid and melt phases were determined by the methods of thermomechanical analysis and the dependence of this parameter on copper concentration was established.

Photoluminescence of Eu- and Sm-doped LiInO2 phosphor powders

Lithium-indium oxide doped with Eu3+ or Sm3+ is prepared by a solid-state chemistry method and its properties are analyzed with respect to its possible application as a phosphor material. X-ray diffraction confirmed that the present synthesis yields a product in tetragonal structural form (space group I41/amd) with no impurity phases. The optical band gaps of 3.4 eV for the Eu3+ sample and 3.5 eV for Sm3+ are found. Photoluminescence emission measurements showed that rare-earth ions substitute In in sites of D2d symmetry with single-exponential emission decays of 1.5 ms for the Eu3+-doped sample and 2.3 ms for the Sm3+ case.

Effect of copper on conductivity of amorphous AsSeyIz

Abstract The effect of copper in AsSeyIz (for y=1.4, z=0.2) on physical and electrical properties has been examined. Temperature dependence of the electrical conductivity has also been determined. Conduction type and activation energies of electrical conductivity have been determined for Cux(AsSe1.4I0.2)100−x glasses. The study has also been concerned with spectral distribution of photoconductivity of bulk glass samples and thin films of analogous composition and with the determination of photosensitivity maxima.

Thermal Analysis of Fe(III) Complexes with Salicylaldehyde Semi-, Thiosemi- and S-methylisothiosemi-carbazones

The paper describes the results of differential thermal analysis of the octahedral Fe(III) complexes of the general formula [Fe(HLn)2]Cl and Fe(HL3)L3, as well as of the corresponding ligands H2Ln (H2Ln — tridentate salicylaldehyde semi thiosemi- and S-methylisothiosemi-carabazones with n=1, 2 and 3 respectively). The decomposition of the complexes involving sulphur-containing ligands (H2L2 and H2L3) starts with sulphur elimination. In case of the complexes [Fe(HL2)]Cl and [Fe(HL3)]Cl sulphur evolves independently, whereas with Fe(HL3)L3 it is eliminated within the SCH3 group. In the former case, sulphur elimination takes place at the same temperature for both complexes. The change in the coordination mode, being a consequence of the replacement of O by S, has no essential effect on thermal stability of the coordination polyhedron. The complexes involving ONN coordination, realized with the H2L3 ligand, exhibit a comparatively highest thermal stability of the coordination polyhedron.

PMMA/Zn 2 SiO 4 :Eu 3+ (Mn 2+ ) Composites: Preparation, Optical, and Thermal Properties

Luminescent composites of poly(methylmethacrylate) (PMMA) and nanophosphors (Zn2SiO4:Mn2+, Zn2SiO4:Eu3+) were prepared by dispersion casting method. It was found that nanoparticles embedded in PMMA matrix preserve their typical phosphorescence emission. The influence of Zn2SiO4 nanofillers on thermal properties of PMMA was also investigated. A shift towards higher glass transition temperatures and slight improvements in thermal stability of the nanocomposites compared to pure PMMA were observed and are discussed herein.

Electronic spectra of Cu(II) crystal complexes with S-methylthiosemicarbazones

Electronic spectra for a series of coordination compounds of copper(II) with tridentant ligands of salicyl aldehyde S-methylthiosemicarbazone and 8-quinoline aldehyde S-methylthiosemicarbazone were investigated. Coordinations of central ions were determined on the basis of X-ray data and IR spectra. Electronic transitions were detected by processing the diffusion-reflection spectra according to theKubelka-Munk theory. Identifications proved the presence of bands corresponding to intraligand transition, charge transfer spectra and the transition of d-d type which are the result of the elimination of d-orbital degeneration for Cu(II) ions in the crystal field. The effect of the symmetry of coordination polyhedrons is discussed.ZusammenfassungEs wurden Elektronenspektren einer Serie von Koordinationsverbindungen des Kupfer(II) mit tridentaten Liganden (Salizylaldehyd-S-methylthiosemicarbazon und 8-Chinolinylaldehyd-S-methylthiosemicarbazon) untersucht. Die Zentralionkoordination wurde durch Röntgenstrahlenuntersuchungen und auf Grund der IR-Spektren festgestellt. Die Elektronenübergänge wurden nach derKubelka-Munk-Theorie aus den diffusen Reflexionsspektren ermittelt. Die Banden wurden den Intraligandübergängen, dem charge-transfer-Spektrum und den d-d-Typ-Übergängen, die als Resultat der Entartungsbeseitigung der Cu(II)-d-Orbitale im Kristallfeld verschiedener Symmetrie entstehen, zugeschrieben.

Softening Temperature of the Amorphous Cu-As-Se-I System

A detailed characterization of softening temperatures of a series of samples of the amorphous Cu-As-Se-I system is presented. Previous investigations showed that the most effective mode of erasing optical information stored in this complex quaternary system of chalcogenide amorphous semiconductors (ChAS) is a thermal treatment of the samples at temperatures close to their softening points.On the basis of the results obtained using a range of thermal methods it was possible to determine the interval of the beginning of the softening process of the glass, as well as the coefficient of linear expansion of the samples before and after their softening.Measurements of the temperature dependence of the thin film transparencies enabled the determination of softening temperatures of such types of samples of the investigated system, including the reversibility of the processes determining their transparency properties.

Thermal decomposition of octahedral Ni(II) complexes with acetone 1-naphthoylhydrazone

The thermal decompositions of acetone 1-naphthoylhydrazone (L) and its octahedral complexes with Ni(II), with the general formula NiL2X2 (X=Cl, Br, NO3 and NCS), were studied in air and nitrogen atmospheres. It was established that the organic ligand is decomposed in an exothermic processes, which is followed by oxidation of the decomposition fragments by atmospheric oxygen. At temperatures below 640°, all the complexes decompose completely, yielding NiO as the final product, which was confirmed by its X-ray analysis. From the difference between the enthalpy changes for the decompositions of the complexes and of the ligand itself, the nature of the final oxide, and the crystal field splitting parameters obtained from optical measurements, the corresponding stabilization energies were determined.ZusammenfassungIn Luft- und Stickstoffatmosphäre wurde die thermische Zersetzung von Azeton-1-naphthoylhydrazon (L) und seinen oktaedrischen Komplexen mit Ni(II) mit der allgemeinen Formel NiL2X2 (mit X=Cl, Br, NO3 und NCS) untersucht. Es wurde festgestellt, daß der organische Ligand in einem exothemen Prozeß einer Zersetzung und einer anschließenden Oxydation der Zersetzungsprodukte durch Luftsauerstoff unterliegt. Unterhalb 640° zerfällen alle Komplexe vollständig und liefern NiO als Endprodukt, welches mittels Röntgendiffraktionsanalyse identifiziert wurde. Aus dem Unterschied zwischen Enthalpieänderungen für die Zersetzung der Komplexe und des Liganden selbst, aus der Art der erhaltenen Oxide und aus den Parametern der durch optische Messungen bestimmten Kristallfeldaufspaltung wurden die entsprechenden Stabilisierungsenergien bestimmt.