Study On Structure And Dielectric Properties Of BZN Ceramics

Bi2O3-ZnO-Nb2O5(BZN) pyrochlore ceramics with high dielectric constant, low loss andsintering temperature have been considered one of the most promising candidate dielectricmaterials for multi-layer ceramic capacitors and microelectronic circuit. Typical dielectricrelaxation can be observed at low temperature and higher dielectric loss occurs at microwavefrequencies，which limited their application. It is considered that the dielectric relaxation maycontribute to the high dielectric loss of BZN ceramics in microwave devices at roomtemperature. In this paper, the relationship between microstructure and dielectric properies ofBi1.5ZnNb1.5O7based ceramics were investigated. The investigation on low temperaturedielectric relaxation of BZN based ceramics will be of great significance to optimize thedielectric properties of microwave low temperature coffered ceramic. The main results arelisted below:1. The effect of Gd3+substitution on the dielectric properties and structure characteristicswas investigated. With Gd3+increasing, the lattice constant of BGZN and BZNG ceramicsdecrease and increase, respectively. And the AV(O’) and AV(O) of BGZN and BZNGceramics are associated with the change of lattice constant. The dielectric constant of BGZNand BZNG ceramics decreases with the increasing of Gd3+amount at room temperature. Withan increase in Gd3+concentration, the degree of dielectric relaxation of BGZN and BZNGceramics decreases and Tmshifts toward lower temperature direction. The activation energyof BGZN and BZNG ceramics decrease with Gd3+increasing.2. Comsidering ionic radius and valance, the effect of Ti4+/Zr4+substitution at A site onthe dielectric properties and structure characteristics was investigated. The crystal structure ofBZNZ ceramics is the cubic pyrochlore structure (α-BZN) when x≤0.15. With an increase inTi4+/Zr4+concentration, the lattice constant of BTZN and BZZN ceramics decrease and thebond valance sum increase, which is proportional to the change of dielectric constant. Thedegree of dielectric relaxation of BTZN and BZZN ceramics decrease and peak temperatureshifts toward lower temperature direction. The activation energy of both ceramics decreasewith the doping concertation increasing.3. The possibility of ion substiting at different sites are discussed with atomisticsimulation calculation. The low temperature dielectric relaxation of Bi1.5ZnNb1.5O7ceramicswas investigated with the sintering process of ceramics and atomistic simulation calculation,which show that the low temperature dielectric relaxation of Bi1.5ZnNb1.5O7ceramics may attributed to the effect of defects in ceramic sintering processing. And the dielectric propertiesand structure characteristics of BBZN ceramics were investigated.