Structure, dielectric, piezoelectric, antiferroelectric and magnetic properties of CoFe2O4-PbZr0.52Ti0.48O3 composite ceramics

Magnetoelectric composite ceramics CoFe2O4-Pb(Zr0.52Ti0.48)O-3(CFO-PZT) with different molar ratios (CFO/PZT = 1:4, 1:5, 1:6 and 1:7) were prepared by combining chemical coprecipitation and sol-gel method. The effects of molar ratio on the structure, dielectric and multiferroic properties were investigated. XRD results indicate that the composites show bi-phase structure, which can be indexed as CFO and PZT. SEM and EDS images present that the grain distribution is nonuniform, the average grain size of both CFO and PZT are near 1 mu m, while they increase slightly with increasing the molar ratio. The dielectric constant is larger than 2000 in low frequency (<1 kHz) while it decreases to near 500 when the frequency is larger than 4 kHz. The dielectric loss of the sample (1:6) is the maximal, while the sample (1:5) shows the smallest one. The Curie temperature of PZT in the composites is is near 350 degrees C, which is larger than that of pure PZT sample (similar to 330 degrees C), indicating the tuning effect of composition on the transition temperature. The samples present a very broad relaxation and higher disorder level, displaying dispersion behavior. The composites show antiferroelectric behavior in high frequency range while it can recover to normal ferroelectric property at low frequency. The antiferroelectric phenomenon gradually disappears after training effect. The composites with molar ratios of 1:4 and 1:6 exhibit better ferroelectricity and lower conductivity, the values of residual polarization (P-r) are 29.11 and 30.03 mu C/cm(2), respectively. The electrostrictive strain is 0.086% at 40 kV/cm when the molar ratio is 1:5, the sample (1:7) shows the smallest value (0.044%). All the samples show ferromagnetic properties, the magnetization decreases with increasing the PZT content. The saturation magnetization (M-s) and residual magnetization (M-r) of the samples decrease as the PZT content in the composite increases. Among them, the composite with the molar ratio of 1:4 shows better magnetic properties, the value of M-r and coercive field are respectively 1.67 emu/g and 404.26 Oe.