Packing defects in alloys of WSe2-NbSe2 system

The system (Tlsub(2)Se)sub(3x)-(Sbsub(2)Sesub(3))sub(1-x) was investigated. In this view the alloys were prepared for all concentration range through x=0.05. The alloys were subjected to roentgenophase (RP), differential thermal (DT) and microstructural analysis as well as to microhardness measurement. State diagram was drawn on the basis of physical and chemical data. The (Tlsub(2)Se)sub(3x)-(Sbsub(2)Sesub(3))sub(1-x) plane is quasibinary. The system contains three compounds: TlSbsub(3)Sesub(5) (phase β), TlSbSesub(2) (phase γ) and Tlsub(9)SbSesub(6) (phase delta), as well as eutectics between the phases γ and delta at x=0.47+-0.01 and 345+-3 deg C. Compounds TlSb3Se5 and TlSbSe2 are melting incongruently, while Tl9SbSe6 melts congruently. Monophase structure of TlSb3Se5 is confirmed by microstructural analysis and microhardness measurement. Chemical compound TlSbSe2 is formed at the equimolar ratio 1:1 of binary components α and epsilon (x=0.25) via peritectic reaction Gsub(x=0.30)+β reversible γ at 440+-3 deg C. Phase transition at 385+-3 deg C was detected by roentgenophase, thermal and dilatometric analysis. Thermal effects at 280+-3 deg C in the alloys with x=0.3-0.7 are due to a possible glass formation. Glass formation is confirmed by exothermal character of effects. Above 385 deg C the alloys with x=0.75-1 produce continuous set of solid solutions on the basis of delta-phase. Upon decrease of temperature this region narrows to 10% (x=0.7-0.8). The alloys with x=0.8-1 are biphase at room temperature and are oxidized rapidly in air