Observations of a regular void array in high purity molybdenum and T.Z.M. irradiated at high temperatures with 2MeV nitrogen ions

Electron microscope observations are presented to demonstrate the existence of a three-dimensional defect array in high purity molybdenum, and in T.Z.M., irradiated at high temperatures with 2 MeV nitrogen ions to doses of approximately 1018 ions/cm2. It is shown that the defect array has a body centred cubic structure with a ‘lattice parameter’ of 220 Å and with crystallographic axes coincident with those of the molybdenum matrix. The identification of the defects as voids is discussed together with possible mechanisms for the array formation.