Abstract
Phase relation and thermoelectric properties of LaSy. (4/35≤y≤93/2) were examined. Three phases (β, γ and LaS) were obtained by the direct reaction of La and S in an evacuated quartz capsule at 1000-C. Single phase 7 -LaSy, which has Th3P4-type structure, was obtained by reaction sintering at 1600-C in a vacuum in the range of 1.33≤y≤51.39.γ-phase easily transforms to 8-phase and the strong reduced atmosphere is necessary for the stabilization of 7-phase. The electrical resistivity (r) and thermoelectric power (a) of 7 -LaS, increase with an increase of sulphur content y. Power factor (α2/r) of LaS1.39 larger than that of laS1.33.
