Abstract
High‐T~m~ (∼270 °C) relaxor ferroelectrics 0.40Pb(Fe~1/2~Nb~1/2~)O~3~–0.34PbZrO~3~–0.26PbTiO~3~ (PFN40‐PZ34‐PT26) with pure perovskite phase were synthesized using conventional ceramic processing via a B‐site oxide mixing route for applications in high‐temperature high‐power‐density electrotransducers and high‐temperature capacitors. The relaxor behavior is confirmed by studying the frequency and temperature dependence of the dielectric response and polarization relaxation. The ceramics exhibit a large room‐temperature dielectric constant of ∼1540 and the dielectric constant is nearly independent of frequency with a temperature gradient of ∂ε/∂T = 5.2/°C in the low‐temperature region 250 K < T < 400 K. A strong frequency dependency and abnormal increase of dielectric constant are observed at temperatures around and below T~m~, which is considered to be correlated with the phase transition from tetragonal ferroelectric phase to cubic paraelectric phase confirmed by high‐temperature X‐ray diffraction measurements. The diffused dielectric behavior arises mainly from the compositional fluctuation and/or the substitutional disorder in the arrangement of cations in the perovskite crystallographic sites. The frequency‐dependent remanent polarization scales well with the existing models of random field states, which indicates that the relaxor behavior correlates with the creation of chemical heterogeneity caused by localized cationic ordering. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)