S. R. Lukic

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.

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.

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.

Transition metal complexes with thiosemicarbazide-based ligands. XI, Dioxovanadium(V) complexes with aromatic aldehyde thio and S-methylisothiosemicarbazones

The thermal decomposition and spectroscopic (reflectance and IR spectra) characterization of the newly synthesized square-pyramidal dioxovanadium(V) complexes of the type NH4[VO2(L)] (L is the dianion of the terdentate ligands salicylaldehyde thiosemicarbazone (ONS), halogen-substituted salicylaldehyde and 2-hydroxy-1-naphthaldehyde S-methylisothiosemicarbazones (ONN)) are described.ZusammenfassungEs wird die thermische Zersetzung und spektroskopische Charakterisierung (Reflexionsvermögen und IR-Spektren) neu synthetisierter Dioxovanadium(V)-Komplexe der allgemeinen Formel NH4[VO2(L)] beschrieben, wobei L das Dianion des dreizahnigen Liganden Salicylaldehyd-thiosemicarbazon (ONS), halogensubstituiertes Salicylaldehyd- bzw. 2-Hydroxy-1-naphthaldehyd-S-methyl-isothiosemicarbazon (ONN) ist.

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.

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.

Metal complexes with pyrazole-derived ligands. XIII. Synthesis and thermal studies of Zn(II) complexes with 3-amino-4-acetyl-5-methylpyrazole

ABSTRACT The thermal decomposition of newly synthesized tetrahedral zinc(II) complexes with 3-amino-4-acetyl-5-methylpyrazole (L) of the general formula ZnX2L2 (X=Cl, Br, I) is described. Application of differential thermal analysis allowed the determination of the mechanism of thermal decomposition of the coordination compounds and of the free ligand. Characteristic temperature intervals for elimination of the particular fragments and total enthalpy changes were determined. The course of decomposition in several successive endothermic and exothermic processes of the complex with iodine and chlorine are quite similar. In these cases, the residue is ZnO. The compound with bromine decomposes with no residue.

Effect of copper on thermomechanical characteristics of amorphous AsSeyIz

The paper describes results of a study of glasses of the type Cux (AsSe1.4 I0.2 )100–x for x =0, l, 5, 10, 15, 20 and 25 at% Cu, by the methods of thermomechanical analysis. Values of the thermal coefficients of linear expansion in solid and visco-plastic phase were determined and the dependence of this parameter on copper concentration was established. The experimental method used enabled the determination of characteristics glass transition temperature and the temperature of the beginning of deformation, and it was found that these parameters increase with increase in the copper content.

Metal complexes with pyrazole-derived ligands

The thermal decomposition of tetrahedral cobalt(II) complexes with 3(5)-amino-4-acetyl5(3)-methylpyrazole (HL) of the general formula [Co(HL)2X2] (X=Cl, Br, I, NCO, NCS) and octahedral [Co(HL)2(H2O)4](NO3)2 and [Co(HL)2−N(CN)2}2] complexes was investigated in air atmosphere in the interval from room temperature to 1000°C. Decomposition of the complexes occurred in several successive endothermic and exothermic processes, and the residue was in all cases CoO.

Thermal stability of the amorphous system Ge20As14(SexS1−x)52I14

Results of thermal investigations of the amorphous five-component chalcogenide system Ge20As14(SexS1−x)52I14 are presented. Differential thermal analysis (DTA), derivative differential thermal analysis (DDTA), and dilatometry were employed to determine the temperatures of softening and partial crystallization of the samples. Thermal treatment of the samples at 1000°C and recording of the corresponding thermogravimetric (TG) and derivative thermogravimetric (DTG) curves allowed an elucidation of the full mechanism of their decomposition, which proceeds via seven characteristic phase transitions.ZusammenfassungChalkogenidsystemes Ge20As14(SexS1−x)52I14 dargelegt. DTA, DDTA und Dilatometrie wurden zur Bestimmung des Erweichungspunktes und der Temperatur für eine partielle Kristalisation der Proben eingesetzt. Thermische Behandlung bei 1000°C und die Aufzeichnung der entsprechenden TG-und DTG-Kurven erlaubte es, ihren über sieben charakteristische Phasenumwandlungen verlaufenden Zersetzungsmechanismus voll zu klären.