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

Multifunctional materials such as the multiferroic compound Pb(Fe1/2Nb1/2)O-3, 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 O-2 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 O-2 atmosphere enhances the dielectric constant by similar to 180 % (with maximum epsilon (r) of 12700 at T (C) = 103 A degrees 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 similar to 275 % (P (max) from 6.2 to 16.8 A mu C/cm(2) and P (r) from 2.4 to 6.7 A mu C/cm(2) at 16 kV/cm), and reduces the electrical conductivity by one order of magnitude (from similar to 1 x 10(-7) to similar to 3 x 10(-8)/Omega 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.