Loosely associated ion interaction in the oxide and oxyfluoride pyrochlores

A dielectric relaxation phenomenon was observed in the substituted pyrochlores. The dielectric behavior could be treated according to the Debye model. The activation energy derived from a coincidental determination of the temperature and frequency dependence of loss factors is approximately 0.23 eV, which can be related to a jump of a loosely associated ion pair formed by the replacement of a cation with different valence and the corresponding formation of a vacancy at normally occupied ion site. The period of atom vibration is of the order of 10/sup -12/ sec or so. The influence of chemical compositions is discussed.