GLASS FORMATION AND PHASE EQUILIBRIA IN THE Tm-As-S AND Tm-As-Se SYSTEMS AND THEIR PROPERTIES

Abstract

The nature of the physicochemical interaction in the Tm-As-S and Tm-As-Se systems was studied along various cross sections by methods of Differential Thermal (DTA), X-Ray Diffraction (XRD) and Microstructural (MSA) Analyzes, measuring their micro-hardness and determining their electrophysical properties. The investigation of the alloys of the system started by studying the properties of the initial components in cooling modes of 7–10deg/min. After establishing the boundary of the glass formation region in the systems, the physicochemical properties of glasses and intermediate phases were studied. Analysis showed that all effects on the thermograms were reversible. The compounds of TmAsS3, TmAs4S7, TmAs2S4, Tm3As4S9 compositions were formed in the As2S3-Tm2S3, As2S3-TmS systems. The compounds of TmAs4S7, TmAsS and TmAs2S4 compositions melted congruently, while the compounds of Tm3As4S9 and TmAsS3 melted incongruently. TmAsSe, TmAsSe3, TmAs4Se7, TmAs2Se4 and Tm3As4Se9 phases were formed in the Tm-As-Se system while Tm3As4Se9 was formed by the peritectic reaction TmSe + L ↔ Tm3As4Se9. Microstructural analysis showed that all alloys of the Tm-As-S, Tm-As-Se cross sections were two-phase, except for the composition of intermediate phases. Proceeding from the results of XRD, the lattice parameters of TmAsS, TmAsS3, TmAs4S7, TmAs2S4, as well as parameters of selenium-containing compound were calculated; it found that it crystallized in the rhombic syngony. Based on the results of physicochemical analysis, it was established that the studied cross sections were quasi-binary sections of the Tm-As-S and Tm-As-Se ternary systems. The phase diagram of cross sections with the participation of sulfur and selenium was plotted using the results of physicochemical analysis; it established that the studied cross sections were quasi-binary sections of the Tm-As-S and Tm-As-Se ternary systems.