The effect of pressure on phase-stability in the Pu–Ga alloy system

Abstract

In examining and analyzing over three decades of research on the transformations involved in Pu–Ga alloys, it is clear that many incongruities and contradictions exist. New analysis shows that under certain processing conditions large amounts of a non-diffracting disordered state exists in Pu–Ga alloys, which I call the amorphous state. The amorphous state is certainly not an equilibrium state, but it can be formed under certain pressure conditions, and more surprisingly once formed can persist for extended times and temperatures. It is believed that the emergence of the amorphous state is closely linked to the 5f-electrons going into a bonding mode. Being a physical state, the amorphous state has distinct physical properties, meta-stabilities, and sensitivities to Ga content. The existence of an amorphous state requires innovative new tools for identification and analysis. The density and compressibility data presented in this paper is one such tool for analyzing the amorphous state, but it requires other knowledge of the materials for proper analysis. Many studies point to radiation damage producing amorphous regions. New computer modeling studies show the existence of amorphous regions and Pu-rich interstitial defects in Pu–Ga alloys.