Perovskite phase formation and electrical properties of Pb(Fe1/2Nb1/2)O3ferroelectric ceramicse

Abstract

Pb(Fe1/2Nb1/2)O3 (PFN) ferroelectric ceramics with pure perovskite structure were synthesized successfully by conventional solid-state reaction method via the direct calcining route and the wolframite precursor route. The feasible formation of pure perovskite phase PFN can be attributed to its appropriate tolerance factor and electronegativity difference. PFN ceramics prepared by the above both methods exhibit broad dielectric response peaks (ϵm) accompanied by large dielectric loss and apparent dielectric frequency dispersion, with temperatures of dielectric maximum (Tm) locating at around 90 °C. 0.25 wt% MnO2 and 0.25 wt% Li2CO3 doping can greatly decrease dielectric loss and sharpen dielectric response peaks of the PFN ceramics synthesized by the above both methods. The dielectric frequency dispersion is also suppressed accordingly. However, Tm of the MnO2- and Li2CO3-doped PFN ceramics maintains almost invariable. The remanent polarization (Pr) of the MnO2- and Li2CO3-doped PFN ceramics prepared by the wolframite precursor method is slightly larger than Pr of those prepared by the direct calcining method. Piezoelectric constant d33 of the 0.25 wt% MnO2-doped PFN ceramics prepared by the direct calcining method is the largest among all the samples synthesized, reaching 134 pC/N. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)