Growth of single crystals of rare-earth metals and binary alloys

Abstract

Single crystals of the heavy rare earth metals Gd, Tb, Dy, Ho, Er have been obtained by three methods: 1. RF induction float zoning in an atmosphere of high purity argon. 2. Recrystallisation in the solid state, using ingots cast in a water cooled copper boat and annealing by induction heating in situ. 3. Growth by solid state electrolysis using DC heating with currents of several hundred amperes. For successful crystal growth by float zoning it has been found that only the highest purity, low oxygen content material is entirely suitable because a high initial oxide content produces crystals with a lineage substructure. The method has the advantage that c-axis seeded crystals can be produced without difficulty. Little purification occurs during the zone melting process. Solid state recrystallisation readily produces crystals but is at present relatively uncontrolled compared with float zoning. Direct current heating (solid state electrolysis) is useful both as a method of crystal growth and for the removal of oxide inclusions from material which has not been sublimed.