Study On Dielectric Relaxation Behavior Of A(Fe_0.5Nb_0.5)O₃?A=Ca?Sr?Ba? Ceramics And Its Modification

Perovskite is a type of materials with unique crystal structure. Generically these materials have a chemical formula ABO3. Since its excellent properties, especially doped defect structures present high relative permittivity and low dielectric loss. They are widely used in many fields including solid dielectric materials, solid fuel cell materials and high temperature heating materials. It has become more and more poular in material, chemistry and physic field. In recent years there has been a considerable amount of interest in the Fe-based compositions.The electricl properties of A(Fe0.5Nb0.5)O3 lead-free ceramics will be enhanced according to doping and processing techology.Lead-free piezoelectric ceramic systems of Ba(Fe0.5-xTixNb0.5)O3 and Ba(Fe0.5Nb0.5-xTix)O3 were fabricated by a conventional solid-state reation in this paper. The sintered temperature, phase structure and dielectric properties were investigated doped with different content of TiO2 for BFN ceramic. Experimental results show that the Ti4+ doping BFN ceramic as a donor makes an key influence the grain boundary, which restricts the migration of oxygen vacancy and depresses dielectric loss factor of BFN ceramic. The dielectric loss factor of BFN ceramic can be supressed effectively between 400k-550 k when the Ti4+ doping BFN ceramic is as a donor at x=0.05.At the same time two different ceramics Ca(Fe0.5Nb0.5)O3 and Sr(Fe0.5Nb0.5)O3were prepared with solid-state reation in this paper, so we can study the phase structure, dielectric properties and dielectric relaxation mechanism. They have two dielectric anomal peaks, and the high temperature diffuse dielectric anomaly was deduced to result from a defect induced dielectric relaxation. The impedance curves shows that the Econ of the two samples were 0.975 eV and 1.004 eV separately, which were associated with doubly-ionized oxygen vacancy. Dielectric modulus was employed to investigate the dominant factor for dielectric properties.