Effect of volume fraction on magnetoelectric coupling effect of Co_(0.1)Cu_(0.9)Fe_2O_4/Ba_(0.8)Sr_(0.2)TiO_3 composite liquid

摘要

Co_(0.1)Cu_(0.9)Fe_2O_4 (CCFO) and Ba_(0.8)Sr_(0.2)TiO_3 (BST) particles were respectively prepared by chemical coprecipitation and hydrothermal method, then CCFO/BST composite liquid was synthesized by distributing surface modified CCFO and Ba_(0.8)Sr_(0.2)TiO_3 particles into insulating silicone oil. Effects of volume fraction (Φ_v= 1%, 2%, 5% and 10%) on the micro-structure, dielectric, ferroelectric and magnetoelectric coupling effect were comparatively investigated. XRD showed that the pure phase of CCFO and BST particles was successfully prepared. CCFO/BST composite particle shows ferromagnetic behavior due to the contribution of magnetic phase CCFO. The dielectric constant of CCFO/BST composite liquid is about 1/25 of the composite particles, and the dielectric constant value of the composite liquid decreases with increasing the volume fraction because the permittivity of silicone oil is far smaller than that of CCFO/BST composite particles. The relative change of dielectric constant of composite liquid under the action of external magnetic field is greater than that of composite particle due to its mobility of particles in liquid. The values of remnant polarization (P_r), coercive field (E_c) and leakage current of CCFO/BST composite liquid increase monotonically with increasing volume fraction, while excessive volume fraction may result in abnormal phenomenon because of the agglomeration of particles. Magnetic field-induced chain structure of the composite liquid has been observed under a light microscope at a magnification of 200. The maximal magnetoelectric (ME) coupling coefficient is about 89.78 V/(cm Oe), which is obtained in the CCFO/BST composite liquid when the volume fraction is 10%.