On the Infrared Absorption Spectra of As-S Glasses

Abstract

Arsenic trisulfide glass is of interest as a material of higher refractive index, transparent in the infra-red and having low melting characteristics.The structure of arsenic trisulfide glass has been studied by X-ray diffraction technique, and the data indicate a short range order arrangements of the atoms similar to those in the crystalline orpiment structure. However, there have been very few reports of structure determinations of sulfide glasses which have higher content of sulfur than that of As2S3. In undertaking to provide the necessary structural information, the infra-red absorption of samples with vorious compositions was examined.As2S3, one of raw materials, is synthesized by passing purified H2S gas into 6N-HCl solution of purified As2O3, and dried at temperatures below 100°C, but it was very difficult to remove the small content of Cl- included in As2S3. This crude As2S3 formed black-red glasses. To obtain blight red glasses, As2S3 must be purified by vacuum distillation.In oftaining the glass, at first, the raw materials were mixed up and melted one hour at 360°C by using porcelain crucible, but in this case it was found by infra-red absorption method that the glass contains some oxygen impurities (Fig. 2, Table. 3). Therefore, the method of preparation of the glass samples was changed in the following way.Sufficiently pure elements that exactly weighted for yielding 5-30 grammes of glass were stored in the thick-walled pyrex-type glass ampoules, which were then evacuated and sealed while still under vacuum. The ampoules were heated up to 600°C or 450°C in a furnace, and then quenched or allowed to cool down to room temperature. Infra-red absorption measurements between 1000-400cm-1 were made through polished parralle-sided discs, approximately 0.2-2 millimeters thick, or through very thin film sandwitched by KBr plates, using a Hitachi-Perkin Elmer Model 125 and/or Japan Spectroscopic DS-402 Grating Infrared Spectrometer or Hitachi Infracord.The results obtained were shown in the Table. 4 anb 5.Kolomites an Pavlov suggested that the absorption band appeared at around 800cm-1 is due to As2Se3. To ascertain their suggestions, the As-S glass samples contained Se (No. 7) were prepared, yet it resulted in no indication of absorption band at around 800cm-1. According to the study by Tanaka et al. on arsenic-sulfur glasses prepared by evaporation under normal pressure, it was suggested that the absorption band appered at around 800cm-1 is attributed to the vibration of As=S bond in the As2S5 glass, while the absorption band at around 790cm-1 is due to the inclusion of arsenic disulfide (As2S2 or As4S4) component dissolved in the As2S3 glass. For the experiments of Kolomiets, the use of pure elements did not bring in the absorption band at around 800cm-1 (from Glass No. 73-83). On the contrary, when unpurified elements were used or arsenic oxide was added to As-S glass, the absorption bands at around 800cm-1 (in the case of high content of S) and around 790cm-1 (in the case of low content of S) appeared. And the absorption band shifted gradually from 790cm-1 to 800cm-1 with increasing S content (as indicated in Table. 4). When arsenic oxide was added to As-S glass, SO2 gas produced by chemical reaction between As2O3 and S was ascertained by the appearance of special infra-red absorption bands (1330cm-1 and 1150cm-1) and by the gas chromatographic analysis. On