Study On Low Temperature Dielectric Relaxor Of α-BZN System Ceramic

Bi₂O₃-ZnO-Nb₂O₅（BZN） system ceramic is an attractive ceramic for future low-temperature-coffered ceramic（LTCC）, multi-layer ceramic capacitors, microelectronic circuitsetc as a result of its low sintering temperature, high dielectric constant, low dielectric loss.However, the ceramic has high dielectric loss at microwave frequency and there is obviouslylow frequency dielectric relaxor at low temperature. In this study, Bi_1.5ZnNb_1.5O₇basedceramics were prepared by a solid phase reaction method. The effect of A-site and B-sitesubstitution with the same and different ions on sintering temperature, phase structure,dielectric properties, crystal chemistry properties and especially dielectric relaxation ofα-BZN was investigated. Studying on the low temperature dielectric relaxation and its impactfactor will be useful to understand the relationship between the structure, composition andproperties of dielectric ceramic materials and optimize the dielectric properties of lowtemperature coffered ceramic in microwave.A-site substitution is that Bi³⁺in A-site substituted by Er³⁺、Y³⁺and M (M=La³⁺、Nd³⁺、Sm³⁺、Sc³⁺).when x（M）≤0.20, the compositions have an only α-BZN structure at roomtemperature, while the other phase appears with Er³⁺and Y³⁺contents exceeding0.15. Itcould be found that the solution of M in α-BZN structure is more than Er³⁺and Y³⁺. At-190oC⁺130oC, the relaxoration behavior in low temperature is clearly observed. Bondtheory and molecular dynamics were proposed for explanation of dielectric relaxation.B-site substitution is that Nb⁵⁺in B-site substituted by Ti⁴⁺、Sn⁴⁺and Zr⁴⁺. With theincreasing of dopants, the lattice size remains unchanged and the dielectric constant decreased.The second phase appears with Ti⁴⁺and Sn⁴⁺contents exceeding0.15while the Zr⁴⁺is0.20.At-190oC⁺130oC, Tmshifts toward higher temperatures with Ti⁴⁺and Sn⁴⁺contentsincreased while the Zr⁴⁺-doped toward lower temperatures.With increasing dopant, Tmshiftstoward higher temperatures as the frequency is increased, and the relaxoration behavior canbe observed in a wide temperature range.The mutual interference of dipoles existed under anexternal electric field and caused the asymmetric dielectric relaxation peak.Fe³⁺can be choosed to substitute for Bi³⁺and Nb⁵⁺of α-BZN ceramics. Compared to AFwith BF, it could be found that AF has a more stable structure while BF has higher dielectricconstnt and board relaxor temperature range.