Microstructure and Microwave Dielectric Properties of Ba3.75Nd9.5Ti18-z (Mg1/3Nb2/3) z O54 Ceramics

The effects of magnesium and niobium substitution for titanium on the microwave dielectric properties of Ba3.75Nd9.5Ti18-z (Mg1/3Nb2/3) (z) O-54 (0 a parts per thousand currency sign z a parts per thousand currency sign 3) ceramics were studied. The temperature coefficient of resonant frequency (tau (f) ) decreased from about +60 ppm/A degrees C to +17 ppm/A degrees C when z a parts per thousand currency sign 1. Excellent quality factor (Qf = 7300 GHz) as well as high dielectric constant (epsilon (r) = 80.96) were obtained. For z a parts per thousand yen 1.5, Nd-2(Ti,Mg,Nb)(2)O-7 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 tau (f) value was found to be related to b-site bond valence (V (B-O)) and unit cell volume (V (m)). Average ionic polarizability (alpha (D)) and relative density evidently influenced the dielectric constant.