INVESTIGATION OF THE NEPTUNIUM-ZIRCONIUM PHASE-DIAGRAM BY DIFFERENTIAL THERMAL-ANALYSIS

Differential thermal analysis (DTA) of Np-Zr alloy specimens has been used to characterize the essential features of the Np-Zr phase diagram . DTA results for seven samples with approximate aggregate composition s of 25, 50 or 75 at% Zr led to the conclusion that there were limited mutual solubilities at the terminal portions of the diagram. The appa rent immiscibility of the high-temperature bcc allotropes of Np and Zr contrasts with the behavior reported for the U-Zr and Pu-Zr systems. X-ray diffraction data have indicated the existence of an intermediate phase at lower temperatures, believed to have a nominal composition o f NpZr2, analogous to the delta-UZr2 phase.