Structural and electrical properties of V‐modified Pb(Fe0.5Nb0.5)O3 ceramics

Abstract

AbstractPolycrystalline samples of Pb(Fe0.5Nb0.5–x Vx)O3, x = 0, 0.05, 0.10, 0.15 were synthesized by a mixed oxide technique. Preliminary structural analysis suggests that the compounds have been formed in single‐phase monoclinic crystal system. Incorporation of V+5 in place of Nb+5 significantly reduces the sintering temperature of the compounds. Scanning electron micrographs of the compounds show that the grains are uniformly and densely distributed over the entire surface of the samples. Detailed studies of dielectric properties (dielectric constant and tangent loss) as a function of frequency (103–106 Hz) and temperature (50–300) °C suggest that Pb(Fe0.5Nb0.5–x Vx)O3 x = 0.0, 0.05 undergoes a ferroelectric–paraelectric phase transition. The phase transition in these compositions has been confirmed with the polarisation measurement. For the composition x = 0.10 and 0.15 ferroelectric phase transition vanishes due the grain size reduction. The presence of loss anomaly at high temperature in all V‐doped Pb(Fe0.5Nb0.5)O3 is related to the charge hopping relaxation. On increase in vanadium content in PFN the grain size reduces below the critical value for ferroelectricity to vanish. The ac conductivity of the compounds was found to increase on increasing temperature suggesting NTCR behavior of the materials. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)