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

Pyrochlores based on the general composition Ln(2)TiO(5) (Ln(2.67)Ti(1.33)O(6.67)) and Ln(2)Ti(2)O(7), where Ln = Y or Yb, have been irradiated through the crystalline amorphous transition with 1 MeV Kr ions at the IVEM-TANDEM facility, Argonne National Laboratory. The results show that the T-c (critical temperature for amorphization) differs significantly between each series, e.g. for Y2TiO5 it is 589 +/- 18 K and for Y2Ti2O7 665 +/- 33 K. The difference suggests that recovery from damage is more rapid with increasing Ln content, i.e. a lower T-c 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. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.