Microwave dielectric properties of SrRE4Si3O13 (RE5La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, and Y) ceramics

Abstract

The apatite type SrRE4Si3O13 (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, and Y) ceramics have been prepared by the conventional solid-state ceramic route. The phase purity and surface morphology of the sintered ceramics were studied using X-ray diffraction and scanning electron microscopy methods. These materials showed poor sinterability and was improved by the addition of a small weight percentage of zinc borosilicate glass. The microwave dielectric properties of these materials were studied for the first time. SrRE4Si3O13 ceramics have a low relative permittivity (epsilon(r)) in the range 9-16, a Q-factor (Q(u) x f) upto 26 000 GHz and a low temperature coefficient of resonant frequency (tau(f)). The SrLa4Si3O13 ceramics possessed a high Q(u) x f of nearly 26 000 GHz but with a high negative tau(f) of -46 ppm/degrees C. The tau(f) of SrLa4Si3O13 ceramics was tuned by the addition of suitable amount of TiO2