MICRO-INDENTATION HARDNESS VARIATION AS A FUNCTION OF COMPOSITION FOR POLYCRYSTALLINE SOLUTIONS IN SYSTEMS PBS/PBTE PBSE/PBTE AND PBS/PBSE

Vickers micro-indentation hardness as a function of composition has been measured for polycrystalline solutions of lead chalcogenide systems and results compared to exsolution tendencies as implied by subsolidus features of the phase diagrams. Each system exhibited a positive deviation from a linear hardness relation between the end member compounds. The most pronounced hardening was observed for PbS/PbTe solutions; the maximum hardness occurs at about 30 mole % PbTe, coincident with a large solubility gap with a solvus maximum (critical point) at about 30 mol % PbTe and approximately 805° C. The least amount of hardening was observed for the system PbS/PbSe, which exhibits no exsolution at temperatures as low as 300° C. The hardness versus composition curve was approximately symmetric about the 50 mol % composition. Intermediate between these two systems, the PbSe/PbTe crystalline solutions exhibited an asymmetric hardness/composition curve with maximum hardness at about 30 mol % PbTe. Partial phase studies indicate the possibility of a solvus maximum at 500 to 600° C on the PbSe-rich side of the diagram. © 1969 Chapman and Hall.