Dielectric, ferroelectric, magnetic and multiferroic properties of xNi0.15Cu0.25Zn0.6Fe2O4-(1-x)Ba0.85Ca0.15Zr0.1Ti0.9O3 composite ceramics

Multiferroic composite ceramics xNi(0.15)Cu(0.25)Zn(0.6)Fe(2)O(4)-(1-x) Ba0.85Ca0.15Zr0.1Ti0.9O3 (x = 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.9 and 1) were prepared by combining chemical co-precipitation method with sol-gel method; the microstructure, dielectric, ferroelectric, magnetic and multiferroic properties were comparatively investigated. XRD results show that all the specimens have obvious bi-phases structure. The grains with larger size are magnetic phase Ni0.15Cu0.25Zn0.6Fe2O4(NCZF), while that of smaller size can be attributed to ferroelectric phase Ba0.85Ca0.15Zr0.1Ti0.9O3(BCZT). The dielectric constant of the sample with x = 0.6 is the largest at low frequency but the specimen x = 0.2 has the highest value of dielectric constant in high-frequency region. When x = 0.9, the ceramic has the largest loss, while it presents the lowest loss value when x = 0.3. The height of the peak decreases with increase in the frequency, and the position of the peak moves to higher temperature range with the decrease in x. The dielectric loss increases sharply with temperature, especially when x = 0.9, when the temperature is higher than 300 degrees C, the dielectric loss reaches hundreds of times under low frequency. Al samples present apparent ferroelectric hysteresis loops, but further characterization shows that the hysteresis may be attributed to leakage current. The remnant polarization(P-r) and coercive field(E-c) do not monotonically change with x, P-r is 0.1576 mu C/cm(2) at 2 kHz when x = 0.6. The magnetization monotonically changes with the x, indicating that there is a strong interfacial interaction between the two phases. Under the action of an external magnetic field of 1 mT, the magnetoelectric (ME) coupling is the strongest (relative polarization change 37%) when x = 0.2.