A. I. Suchkov

High-Purity As-S-Se and As-Se-Te Glasses and Optical Fibers

We describe a procedure for the preparation of As-S-Se and As-Se-Te glasses with low contents of gas-forming impurities (hydrogen, oxygen, and carbon) via melting of extrapure-grade elements in an evacuated silica ampule and purification of the melt by chemical distillation. The impurity concentrations in the glasses thus prepared have been reduced to the following levels: hydrogen, <0.02; oxygen, 0.2; carbon, <0.02; silicon, <0.4 ppm by weight. Using the double-crucible method, we have fabricated glass fibers with various ratios of the core and cladding diameters (1: 25 to 9: 10), protected with a tetrafluoroethylene/1,1-difluoroethylene copolymer coating, which have an average bending strength of 0.5–1 GPa. The minimal optical losses are 150 dB/km at 6.6 μm in multimode As-Se-Te glass fibers and 60 dB/km at 4.8 μm in As-S-Se glass fibers. The effect of microinhomogeneities in the melt on the optical performance of arsenic sulfoselenide glass fibers fabricated by the double-crucible method is examined.

Origin of microinhomogeneities in As-S-Se glass fibers fabricated by the double-crucible method

The optical losses in sulfoselenide glass fibers fabricated by the double-crucible method are shown to rise in going from the first-drawn portion to the back end of the fiber. Optical microscopy, IR and Raman spectroscopy, energy-dispersive x-ray microanalysis, and differential scanning calorimetry data indicate that fiber drawing is accompanied by the development of microinhomogeneities of the chemical and phase compositions of the melt, which are responsible for the increased scattering losses. The microinhomogeneities originate from phase segregation of the molten glass.

X-ray fluorescence determination of the macroscopic composition of As-S, As-Se, and As-S-Se glasses

An X-ray fluorescence technique has been developed for determination of the macroscopic composition of As-S-Se, As-S, and As-Se chalcogenide glasses. Reference samples for calibration have been prepared by direct elemental synthesis. The calibration error has been estimated.

Coprecipitation of tellurium and molybdenum oxides from aqueous solutions

We report the preparation of mixtures of tellurium and molybdenum oxides of controlled composition through the precipitation of tellurous and molybdic acids from hydrochloric acid solutions of tellurium(IV) and molybdenum(VI) compounds. We have established general trends in the distribution of macrocomponents between the precipitate and solution and shown the feasibility of quantitative tellurium(IV) and molybdenum(VI) precipitation in a weakly acidic medium. After drying and calcination, the precipitates were tested as TeO2-MoO3 glass batches.

Adhesion mechanism of destruction of silica-glass surface during the preparation and treatment of optical glassy arsenic Chalcogenides

Adhesion of As–S and As–Se glasses to silica glass is studied by means of the steady detachment method. The results demonstrate that the adhesion strength of the boundary of solid phases increases with the content of chalcogens in the composition of glass. It is found that adhesion of arsenic sulfide glasses with sulfur content over 65% to silica glass exceeds the tensile strength of the silica glass during the process of solidification and annealing of chalcogenide preforms. The adhesion of arsenic chalcogenides to silica glass is determined to be the reason of chalcogenide glass contamination by heterophase inclusions.

Preparation of extrapure Ga2S3 by reacting GaI3 with sulfur

This paper describes a process for the preparation of extrapure gallium(III) sulfide by reacting gallium(III) iodide with sulfur in an evacuated two-zone quartz glass reactor. The maximum synthesis temperature was 350°C. The residual iodine was removed by calcining the powders at temperatures from 500 to 650°C. The gallium(III) sulfide yield was 93–96% of theoretical yield. The samples were characterized by X-ray microanalysis, X-ray diffraction, and laser mass spectrometry and were shown to contain the following impurities (ppm): silicon, 20–28; iron and calcium, 0.5–0.6; potassium, 0.3–0.7; chromium, 0.2; chlorine, 70–100; aluminum, 0.05–0.1; and phosphorus, 0.1–2. The iodine content varied from 0.04 to 1.8 at %, depending on calcination temperature and time.

Preparation of monolithic ZnSxSe1-x layers via chemical vapor deposition followed by hot isostatic pressing

A process is described for the preparation of monolithic ZnSxSe1−x (0.1 < x < 0.6) plates uniform in composition. The effect of hot isostatic pressing on the optical and structural properties of zinc sulfoselenide is examined.

Formation of second-phase inclusions in molten As2Se3 via chemical transport of carbon

Experimental evidence is presented that, in a closed system containing the As2Se3melt and vapor, a temperature gradient gives rise to the chemical transport of carbon, combined with Se, from the hot (700–900°C) to the cold (600°C) zone. As a result, submicron-sized (0.07–0.18 μm) carbon inclusions are formed in the As2Se3melt. The results shed light on the role of second-phase inclusions in the degradation of the optical quality of glassy As2Se3 .

Effect of Polishing Conditions on the Optical Properties of Zinc Selenide Surfaces

The effects of the polish time and the pressure applied to the sample on the quality of polycrystalline ZnSe surfaces prepared by mechanical polishing with fine-particle abrasives on wheels made of pitch–colophony resins are studied. The results indicate that, using 1-μm alumina as an abrasive and distilled water as an extender, the fourth surface finish class (RF Standard GOST 11141-84) with deviations from planarity less than half of an interference fringe at a sample diameter of up to 40 mm can be achieved at pressures applied to the sample from 30 to 35 kPa and polish times longer than 225 min. The material removal rate under the optimal polishing conditions is 0.03 μm/min.

Preparation of ZnGa2S4 by reacting GaI3 and ZnI2 with sulfur

We have carried out thermodynamic modeling of the GaI3–S and ZnI2–S systems by the method of equilibrium constants and calculated the chemical compositions of the condensed and vapor phases in the temperature range 200–500°C. Our experimental data demonstrate the feasibility of preparing zinc thiogallate by reacting gallium(III) iodide and zinc(II) iodide with sulfur. Synthesis was carried out at a temperature of 450°C over a period 2 h, followed by calcination of the product at 650°C in order to remove the residual iodine. The practical ZnGa2S4 yield was 92–94%.