Improvement of the dielectric and ferroelectric properties of multiferroic Pb(Fe1/2Nb1/2)O3 ceramics processed in oxygen atmosphere

Abstract

Multifunctional materials such as the multiferroic compound Pb(Fe1/2Nb1/2)O3, are of great interest from the academic and technological points of view. However, the occurrence of Fe2+ and oxygen vacancies originated during the sintering process increase the dielectric loss and electrical conductivity, detrimental to optimal device performance. Here, a report on the effects of a saturated O2 atmosphere used during the calcination and sintering stages is presented. A comparative study of structural, morphological, and physical properties with those obtained for samples sintered in air or in its own atmosphere, is presented. The O2 atmosphere enhances the dielectric constant by ~180 % (with maximum e r of 12700 at T C = 103 °C and dielectric loss smaller than 0.01 independent of frequency and temperature below 100 kHz and T C, respectively), the maximum and remanent polarization by ~275 % (P max from 6.2 to 16.8 µC/cm2 and P r from 2.4 to 6.7 µC/cm2 at 16 kV/cm), and reduces the electrical conductivity by one order of magnitude (from ~1 × 10−7 to ~3 × 10−8/Ω cm at 1 kHz at room temperature). Additionally, a pronounced ac positive temperature coefficient of resistivity effect, strongly dependent on frequency and with potential barrier values from 0.2 eV at 1 kHz to 0.71 eV at 500 kHz, is associated with the highly resistive and capacitive behavior of the grain boundary.