The Effect of PbO-Nonstoichiometry on Dielectric and Semiconducting Properties of PbFe_0.5Nb_0.5O₃-Based Ceramics

Abstract

Dielectric, X-ray and electric resistivity studies of nonstoichiometric PbFe_0.5Nb_0.5O₃-based ceramics obtained by solid-state reaction route with PbO/(Fe_0.5Nb_0.5O₂) molar ratio differing from 0.6 to 1.2 have been carried out. Deviation from stoichiometric PbFe_0.5Nb_0.5O₃ composition leads to formation of diphase mixtures containing ferroelectric perovskite PbFe_0.5Nb_0.5O₃ phase and nonferroelectric PbO or pyrochlore Pb₃Nb₄O₁₃ phases and to decreasing of the dielectric permittivity values. The electric resistivity of PbFe_0.5Nb_0.5O₃ ceramics decreases dramatically when the sintering temperature increases. The formation of the pyrochlore phase decreases the room temperature resistivity values while the anomaly of the positive temperature coefficient of resistivity above the ferroelectric Curie temperature gradually diminishes with the increase of the pyrochlore content.

Keywords:

• Dielectric permittivities
• ferroelectric ceramics
• lead iron niobate
• stoichiometry
• positive temperature coefficient of resistivity

Acknowledgment

This study is supported in part by the Russian Foundation for Basic Research (RFBR) grant 09-02-92672 IND_a.