Effects of addition of BiFeO3 on phase transition and dielectric properties of BaTiO3 ceramics

Samples of xBiFeO(3)-(1 - x)BaTiO3 (x = 0, 0.02, 0.04, 0.06, 0.07 and 0.08) were synthesized by solid state reaction technique and sintered in air in the temperature range 1,220-1,280 A degrees C for 4 h. X-ray diffraction data showed that 2-8 mol% BiFeO3 can dissolve into the lattice of BaTiO3 and form single perovskite phase. The crystal structure changes from tetragonal to cubic phase at room temperature when 8 mol% of BiFeO3 was added into BaTiO3. Scanning electron microscope images indicated that the ceramics have compact and uniform microstructures, and the grain size of the ceramics decreases with the increase of BiFeO3 content. Dielectric constants were measured as functions of temperatures (25-200 A degrees C). With rising addition of BiFeO3, the Curie temperature decreases. For the sample with x = 0.08, the phase transition occurred below room temperature. The boundary between tetragonal and cubic phase of the BiFeO3-BaTiO3 system at room temperature locates at a composition between 7 and 8 mol% of BiFeO3. The diffusivity parameter gamma for compositions x = 0.02 and x = 0.07 is 1.21 and 1.29, respectively. The relaxor-like behaviour is enhanced by the BiFeO3 addition.