Study On Dielectric Properties Of Bi₂O₃-ZnO-Nb₂O₅ System Ceramic

Bi2O3-ZnO-Nb2O5 system ceramic is an attractive ceramic for future low-temperature -coffered ceramic (LTCC), multi-layer ceramic capacitors, microwave filter, microelectronic circuits etc as a result of its low sintering temperature, high dielectric constant, low dielectric loss, near-zero temperature coefficient of the dielectric constant. In this study, Bi2(Zn1/3Nb2/3)2O7 ceramics were prepared by a solid phase reaction method, The effect of A-site and (A, B)-site substitution on sintering temperature, phase structure, dielectric properties and especially dielectric relaxation ofβ-BZN ceramics was investigated. Studying on the the dielectric relaxation will be useful to understand the relationship between the structure, composition and properties of dielectric ceramic materials and improve the dielectric properties of BZN based ceramics in microwave.A-site substitution is that Bi3+ in A-site substituted by Na+ (RNa=0.118nm) and Li+ (RLi=0.092nm). The substituted samples sintered under 900℃have high bulk density and uniform distribution grains. The cubic phase appears with Na+ contents exceeding 0.2 and other phase appears with Li+ contents exceeding 0.1. At -30℃～+130℃, The relaxation behavior is obviously observed. The activation energy involved in the relaxation processes is about about 0.4eV for Na+ substitution and 0.3 eV for Li+ substitution. Defect dipole and distortion of crystal lattice were proposed for explanation of dielectric relaxation of Na-Ni doped Bi2(Zn1/3Nb2/3)2O7 ceramics.(A, B)-site substitution that Bi3+ in A-site substituted by Na+ with same content and Nb5+ in B-site substituted by Sn4+, Ti4+, Zr4+, Ni2+ with different contents. The permittivity of substituted samples is enhanced. At -30℃～+130℃, The relaxation behavior is obviously observed. The slopes of two sides of dielectric curves are different. The mutual interference of dipoles existed under an external electric field and caused the asymmetric dielectric relaxation peek. Two relaxation peak appeared when the substitution of Ni2+ reached 0.2. With the future increasing of substitution, the temperature of the permittivity maximum shifts to higher temperature and the activation energy involved in the relaxation processes increases and the distance between two relaxation peaks becomes longer.