Dielectric, complex impedance and electrical conductivity studies of the multiferroic Sr2FeSi2O7-crystallized glass-ceramics

In this paper, the Sr2FeSi2O7-crystallized glass-ceramics was successfully prepared by conventional melt casting followed by heat treatment method in the SrO-Fe2O3-SiO2-B2O3 glass system. The XRD, SEM and EDS results show that the crystalline Sr2FeSi2O7 is obtained with uniform microstructures and its grain size around 0.5-0.7 μm. The magnetization hysteresis (M−H) loop of the glass-ceramics exhibits typical ferromagnetic behavior with saturation magnetization values Ms = 10.527 emu/g and coercive field Hc = 210.462 Oe. In addition, some electric characteristics of (dielectric, impedance and conductivity) of the glass-ceramics have been investigated in a wide rang of frequency (20 Hz-2000 kHz) and temperature (220-440 °C) ranges. The dielectric dispersion phenomenon in ε′ and ε'' with frequency can be explained by Maxwell-Wagner model. Moreover, the complex impedance measurement provides a clear rationalization of the Maxwell-Wagner type of relaxation, namely crystalline phase and glassy phase contributions. The step-like feature of ac conductivity, plateau and dispersive regime can be explained by the Jump Relaxation Model (JRM) and dc conductivity is found to obey the Arrhenius law. The temperature dependence of n is investigated to explain the conduction mechanism in the different parts, which is attributed to the CBH model in Part-1 and the OLPT model in Part-2. The investigations of both complex impedance and conductivity show the NTCR character of the sample.