Ion irradiation of novel yttrium/ytterbium-based pyrochlores: The effect of disorder

Pyrochlores based on the general composition Ln2TiO5 (Ln2.67Ti1.33O6.67) and Ln2Ti2O7, where Ln=Y or Yb, have been irradiated through the crystalline–amorphous transition with 1MeV Kr ions at the IVEM-TANDEM facility, Argonne National Laboratory. The results show that the Tc (critical temperature for amorphization) differs significantly between each series, e.g. for Y2TiO5 it is 589±18K and for Y2Ti2O7 665±33K. The difference suggests that recovery from damage is more rapid with increasing Ln content, i.e. a lower Tc for amorphization. These results are discussed in the context of the melting points of each phase, atomic disorder, the pyrochlore–fluorite order–disorder transition and the implications for oxide dispersion-strengthened additives.