A transmission electron microscopic study was made of neutron-irradiated bulk

samples. Clear evidence was found that neutron irradiation created nanometric

amorphous regions within the crystal lattice. The density of these defects scaled

correctly with the neutron dose. These defects, whose size matched the coherence

length, acted as pinning centers and were responsible for the marked increase in the

critical current density at high fields and for shifting the maxima of the pinningforce

curves towards higher fields.

Direct TEM Observation of Nanometric-Sized Defects in Neutron-Irradiated MgB2

Bulk and Their Effect on Pinning Mechanisms. A.Martinelli, C.Tarantini,

E.Lehmann, P.Manfrinetti, A.Palenzona, I.Pallecchi, M.Putti, C.Ferdeghini:

Superconductor Science and Technology, 2008, 21[1], 012001