High-temperature Dielectric Properties Of Znnb2_O6Microwave Dielectric Ceramics

With the continuing proliferation of wireless communications technologies operating at microwave frequencies, there has an ever-increasing demand for low-cost, but high performance dielectric ceramics. The application of microwave ceramic components becomes an inevitable trend, resulting in the rapid progress in related microwave ceramic materials. Microwave dielectric ceramics have been widely investigated for the use of resonators and filters in the satellite and mobile communication systems.In recent years, ZnNb2O6ceramics has been became research focus in today’s academic circles because it has advantages such as excellent dielectric properties and low fabrication temperature and cost. These promising advantages stimulate many attentions to this material and most of them were focused on the effects of additives on the microwave dielectric properties as well as low temperature sintering behavior. This promising material requires a full characterization of the dielectric properties.In this paper we reported the dielectric properties of ZnNb2O6ceramics at higher temperatures. The sample of ZnNb2O6has been prepared through the solid state reaction technique. The structures, features properties of the samples were characterized using XRD and SEM. Dielectric properties of this material have been measured in detail as functions of temperature (between200and800℃) and frequency (20Hz-10MHz). Two peaks around400℃and650℃were observed in the tan δ(T). Two dielectric relaxations were found with the activation energies of0.65eV and0.32eV for the low-and high-temperature relaxation.The low-temperature dielectric relaxation situated at around400℃was found to be related to oxygen vacancys. By means of complex impedance analysis the low-temperature relaxation was identified to originate from the space-charge dielectric relaxation mechanism related to the grain boundaries. The high-temperature one appears at about650℃was also ascribed to oxygen vacancys. Based on the analysis of the absence of significant mismatch between Z"(ω) and M"(ω) peaks, the observed high-temperature relaxation process is due to the short distance charge transport.