Study of microstructure, dielectric and magnetoelectric properties of the lead free co-fired BaTiO_3-CoZn_(0.2)Fe_(1.8)O_4-BaTiO_3 trilayer composites

摘要

Multiferroic co-fired trilayer BaTiO_3-CoZn_(0.2) Fe_(1.8)O_4-BaTiO_3 (BT-CZF-BT) composites are synthesized by conventional solid state reaction method. The investigation of the cross-sectional view of the trilayer composites using scanning electron microscopy in the back scattered mode shows a clear interface between the different layers. The energy dispersive spectroscopy line scanning across the interface reveals that slight inter-diffusion of elements has occurred at interface between the different BT and CZF layers. Furthermore, the dependence of dielectric properties on the frequency and temperature has been examined. In the dielectric constant versus temperature plots, a dielectric anomaly is observed near the ferroelectric to paraelectric phase transition of the BT, which shifts towards high temperature side as frequency increases for all the samples, demonstrating relaxor like behavior. In addition, broad peaks are also noticed in the loss tangent versus temperature plots in the same temperature range. The estimated values of the activation energy for the laminated composites from the Arrhenius plots, suggests that the observed dielectric behavior might be attributed to the oxygen vacancies. The influence of the magnetic layer (CZF) thickness and dc magnetic field on the magnetoelectric coefficient (α_E) of the laminated composite is studied. The α_E of the laminated composites is found to increase with increasing thickness of the CZF layer, with maximum value achieved is 0.89 mV/cm Oe at 1400 Oe.