Dielectric properties and aging effects of manganese modified lead iron tungstate relaxor ceramics

The dielectric properties of (1−x)Pb(Fe2/3W1/3)O3·xPbTiO3 solid solutions were investigated from 102 to 106 Hz in the temperature range 150–600 K. The phase transition of Pb(Fe2/3W1/3)O3 (PFW) was shifted by PbTiO3 (PT) additions to higher temperatures at a rate of 6.3 K/mol% of PT. The temperature dependence of dielectric permittivity showed a sharper transition as the PT content increased. Dielectric measurements in a wide temperature range showed the presence of a second set of dielectric peaks at higher temperatures (350–600 K), besides the ferroelectric–paraelectric phase transition. This second set of peaks vanished when the samples were annealed in nitrogen. The activation energy values for the second relaxation varied between 0.50 and 0.63 eV, in agreement with the conduction activation energy determined for each sample. This relaxation is apparently related to electron holes.