AGING BEHAVIOR OF XPB(FE2/3W1/3)O3.(1-X)PB(FE1/2NB1/2)O3 CERAMIC

The aging behavior of a series of lead perovskite dielectrics with the compositions xPb(Fe2/3W1/3)O3.(1 - x)Pb(Fe1/2-Nb1/2)O3, where 0 less-than-or-equal-to x less-than-or-equal-to 1, and the effect of dopants were studied. Below the Curie temperature (T(c)), the capacitance and the dissipation factor (tan delta) decrease approximately linearly with logarithmic time. The aging rate depends on the temperature difference, DELTA-T, between the aging temperature and T(c), and on the dopant concentration, but is independent of the measurement frequency between 1 and 1000 kHz. The maximum aging rate is about 3% per decade of time for capacitance and 5% per decade for tan delta at 1 mol% dopant concentration, and increases to 6.3% for capacitance and 8.5% for tan delta at 0.7 mol% dopant concentration. These results are consistent with an aging mechanism caused by changing ferroelectric domain structure with time, as proposed for BaTiO3.