Stability of Pyrochlore Oxides

摘要

A Contour plot of the disorder reaction energies across a wide variety ofA(sub2)B(sub2)O(sub7) pyrochlore oxides has been produced using atomistic simulation calculations based on energy minimization techniques. Cations studied range from LU(sup3+) to La(sup3+) on the A site and Ti(sup4+) to Ce(sup4+) on the B site. The results relate the experimentally observed stability range of the pyrochlore structure to A and B cation size and disorder. Disorder enthalpies decrease dramatically with increasing B cation size whilst the rate of increase with A cation size depends markedly on the particular B cation. The association of anion Frenkel and cation antisite disorders is found to be of importance.