Effects of Europium Substitution on the Microstructure and Electric Properties of Bismuth Ferrite Ceramics

Bi1-x Eu (x) FeO3 (x=0.00-0.15) ceramics were synthesized by solid state reaction method with rapid liquid phase sintering process at different europium content and the microstructure and electrical properties of the samples were investigated. X-ray diffraction (XRD) studies show that europium substitution has changed the structure of BiFeO3 from rhombohedral R3c to orthorhombic Pnma and decreased the impurity phase. Raman spectra results also conform that a structure transition occurs at about x=0.20, and indicate that the Eu substitution at Bi site can obviously affect the Bi-O bond. Impedance analyzer measurements show that both dielectric constant and dielectric loss are strongly dependent on the Eu content. The dielectric constant of the Bi1-x Eu (x) FeO3 increases with increasing Eu content from 0.00 to 0.20, then decreases with increasing Eu content from 0.20 to 0.30. The dielectric constant measured at 100 Hz is 542.0 for the x=0.20 sample, which is about 8.5 times as big as that for unsubsitituted BiFeO3. The dielectric loss can be effectively decreased by the substitution of Eu for Bi. In addition, the leakage current measurements show that the substitution of Eu can effectively reduce the leakage current density of BiFeO3.