Zixiong Sun

Ferroelectric and Magnetic Properties of SrO-B2O3-SiO2 Glass-Doped BiFeO3 Ceramics

BiFeO3 ceramics doped with varying amounts of SrO-B2O3-SiO2 glass, i.e., xwt% (x = 0, 0.2, 0.4, 0.6, 0.8) have been successfully developed via a solid state reaction route. Phase identification using XRD showed that a relatively pure BiFeO3 phase could be obtained at the reaction temperature of 760° for 2h. The sintering temperature of these glass-doped BiFeO3 ceramics was controlled at about 800°, on the basis of the studies of the optimized bulk density, although the bulk density varied with the different doping levels of SrO-B2O3-SiO2 glass. The dielectric constant and dielectric loss of sintered ceramics are affected by the glass doping level, while the BiFeO3 doped with 0.6% SrO-B2O3-SiO2 glass exhibited a comparatively higher dielectric constant value and minimum dielectric loss. At x = 0.6 and 0.8, the glass-doped BiFeO3 ceramics show saturated hysteresis loops with the respective saturation polarizations of 1.2μC/cm2 and 1.4μC/cm2. Too high a glass doping level in BiFeO3 gave rise to weakened magnetic behavior.

Dielectric Properties of (1-x)BaTiO3-xBaFe12O19 Composite Ceramics

The composite ceramics of (1-x)BaTiO3-xBaFe12O19 (x = 0.2, 0.4, 0.5 and 0.6) were prepared by solid state method. The phase formation and diphase microstructure of the composite samples were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that ferroelectric BaTiO3 can well coexisted with the magnetic phase BaFe12O19. The electric and dielectric properties of the obtained composites were investigated. The electrical conduction and dielectric constant of the composites increased with the increase of BaFe12O19 contents. The high values of conductivity and dielectric constant near 250°C were due to the effect of space charges that played an important role in the composites. (1-x)BaTiO3-xBaFe12O19 composites exhibited a high value of dielectric constant at low frequencies and high temperatures. At x = 0.4, the composites showed usual dielectric dispersion with increasing frequency.

Giant Dielectric Behavior and Complex Impedance of Cu2+ Doped Ba0.9Ca0.1Ti0.9Zr0.1O3 Ceramics Prepared by Hydrothermal Method

Ceramics in the solid solution system, Ba0.9Ca0.1Ti0.9Zr0.1O3-xCu2+ (BCTZ-Cu2+) were prepared by hydrothermal method assisted by microwave sintering. Single orthorhombic phase perovskite-type X-ray diffraction patterns were observed for all doped ceramics, while the addition of Cu2+ had no significant effects on the microstructure of BCTZ-Cu2+ ceramics. Dielectric measurements indicated a significant increase in dielectric constant and a slight increase in Curie Temperature (TC) with increasing x, and the Maxwell-Wagner effects can be detected at lower x. The impedance complex plane plots of sample for x=0.16 turned into one semicircular arc at 200°C from a single line at 100°C and then to two semicircular arcs at 300°C and 400°C, which can be analyzed as four different equivalent circuits. Both the Rg and Re measured at 400°C decreased with increasing x.