SOLID-STATE CRYSTAL-GROWTH OF RARE-EARTH-METALS AND ALLOYS ADOPTING THE HCP CRYSTAL-STRUCTURE

The results of 34 solid-state recrystallization crystal growth attempts on rare earth metal elements and rare earth-rare earth alloys which adopt the hexagonal close-packed crystal structure are presented. Following a procedure which involved annealing ingots which had been strained by fast cooling from the melt, a heat treatment recipe of annealing for at least 40-60 h at a temperature equivalent to 85% of the absolute melting temperature or 95% of any h.c.p.-b.c.c. transformation temperature, whichever was the lower, was deduced to lead to the most extensive grain growth. The potential advantages of solid-state crystal growth over melt growth for these materials were found to be experimental simplicity, the preparation of crystals with improved crystal quality and lower volatilization losses for higher vapour pressure materials.