Microstructure and Microwave Dielectric Properties nof Ba3.75Nd9.5Ti18−zn (Mg1/3Nb2/3)n zn O54 Ceramics

摘要

The effects of magnesium and niobium substitution for titanium on the microwave dielectric properties of Ba3.75Nd9.5Ti18−z (Mg1/3Nb2/3) z O54 (0 ≤ z≤ 3) ceramics were studied. The temperature coefficient of resonant frequency (τ f ) decreased from about +60 ppm/°C to +17 ppm/°C when z ≤ 1. Excellent quality factor (Qf = 7300 GHz) as well as high dielectric constant (ε r = 80.96) were obtained. For z ≥ 1.5, Nd2(Ti,Mg,Nb)2O7 secondary phase appeared which would obviously influence the microwave dielectric properties. As z varied from 0 to 3, matrix grain size degraded which would obviously deteriorate the microwave dielectric properties by conducting more pores, especially the Qf value. The τ f value was found to be related to b-site bond valence (V B-O) and unit cell volume (V m). Average ionic polarizability (α D) and relative density evidently influenced the dielectric constant.