Ferroelectric properties and ac conductivity studies of yttrium modified Pb(Fe0.5Nb0.5)O3 ceramics

Using a high-temperature standard solid-state reaction (i.e., mixed oxide) method several yttrium modified ferroelectric ceramics of type Pb_1−xY_x(Fe_0.5Nb_0.5)_1−x/4O₃ (PYFN)with different concentration (x = 0.00, 0.02, 0.04, 0.06, 0.08) were prepared. Preliminary X-ray structural analysis reveals that all the samples were crystallized in monoclinic crystal system. The crystal structure is almost invariant with small Y-concentration. Microstructure of the samples exhibits grain growth on increasing Y content. Curie temperature of Y-substituted samples decreases slightly as compared to that of PFN (Pb(Fe_1/2Nb_1/2)O₃). However, Y substitution results in a notable enlargement of remnant polarization (2P_r). The 2P_r of PYFN (x = 0.02) reaches to a large value (23 μC/cm²) which is nearly 5 times greater than that of x = 0.00 (4.6 μC/cm²). A phenomenological model (i.e., ferroelectric capacitor model) used to simulate hysteresis loops was found to be suitable to explain experimental results. Jonscher's single power law (σ_ac(ω) = σ(0) + Aωⁿ) was well fitted to the frequency dependence of conductivity for all the samples.