Microwave dielectric properties and low-temperature sintering of cerium oxide for LTCC applications

Abstract

The effect of glass additives on the microstructure, densification, and microwave dielectric properties of cerium oxide for low-temperature co-fired applications was investigated. Different weight percentages of quenched glass such as B2O3, B2O3-SiO2, Al2O3-SiO2, ZnO-B2O3, BaO-B2O3-SiO2, MgO-B2O3-SiO2, PbO-B2O3-SiO2, ZnO-B2O3-SiO2, 2MgO-Al2O3-5SiO(2), LiO-B2O3-SiO2, Bi2O3-ZnO-B2O3-SiO2, and LiO-MgO-ZnO-B2O3-SiO2 were added to CeO2 powder. The crystal structure of the ceramic-glass composites was studied by X-ray diffraction, microstructure by scanning electron microscopy, and phase composition using the energy-dispersive X-ray analysis technique. The microwave dielectric properties such as relative permittivity (epsilon(r)), quality factor (Q(u)xf), and coefficient of temperature variation of resonant frequency (tau(f)) of the ceramics have been measured in the frequency range 4-6 GHz. Addition of B2O3 and Bi2O3-ZnO-B2O3-SiO2 lowered the sintering temperature of ceria to about 900 degrees C. The 20 wt% B2O3 and 10 wt% Bi2O3-ZnO-B2O3-SiO2-added CeO2 and sintered at 900 degrees and 950 degrees C showed: Q(u)xf=24 200 and 12 000 GHz, epsilon(r)= 13.2 and 22.4, and tau(f)=-46 and -57.2 ppm/degrees C, respectively