Metastable structures of splat-cooled and vapour- depodited lead and antimony films

Abstract

An apparatus for splat quenching in a vacuum and in controlling ambients by the "gun" technique was set up and a cooling rate of approximately 10⁸ K s^-1 was achieved. Splat-quenched lead foils exhibit an h.c.p. structure which transforms to the equilibrium f.c.c. structure at temperatures above 270°C and corresponds to the high pressure phase of lead. Antimony foils prepared by splat quenching show the existence of simple cubic, f.c.c. tetragonal and distorted rhombohedral metastable structures. The metastable rhombohedral phase tranforms to the equilibrium rhombohedral phase on heating while the simple cubic, f.c.c. and tetragonal phases transform to an h.c.p. structure. The simple cubic and h.c.p. phases correspond to the known high pressure phases of antimony. Films prepared by vapour deposition at room temperature show the same metastable f.c.c. and rhombohedral phases as those observed in splat-quenched foils. Antimony films deposited at liquid air temperatures are amorphous. No metastable structure was observed in lead films quenched from the vapour under similar conditions.