Microwave dielectric properties and low-temperature sintering of (1-x)CeO2-xBaTi4O9 ceramics

(1-x)CeO2-xBaTi(4)O(9) ceramics were prepared by the solid-state ceramic route. The structure and microstructure of the ceramics were studied using X-ray diffraction (XRD) and scanning electron microscope. XRD patterns indicate that (1-x) CeO2-xBaTi(4)O(9) ceramics were of a two-phase composite consisting of fluorite CeO2 and BaTi4O9. The microwave dielectric properties such as relative permittivity (epsilon(r)), quality factor (Q(u) x f), and coefficient of temperature variation of resonant frequency (tau(f)) of the ceramics have been measured in the frequency range 4-6 GHz by the resonance method. The 0.5CeO(2)-0.5BaTi(4)O(9) samples sintered at 1260 degrees C/2 h exhibit excellent microwave dielectric properties: epsilon(r)=34.5, Q(u) x f = 20,750 GHz (at 4.2 GHz) and tau(f)= 1.8 ppm/degrees C. The density, dielectric constant, and temperature coefficient of resonant frequency of mixtures predicted by the appropriate mixing relations agree well with the experimental values. The addition of B2O3 and CuO significantly lowered the sintering temperature of 0.5CeO(2)-0.5BaTi(4)O(9) ceramic to 950 degrees C. The 0.5CeO(2)-0.5BaTi(4)O(9) + 12 wt% B2O3 + 1 wt% CuO sintered at 950 degrees C for 4 h showed epsilon(r)=20.6, Q(u) x f = 17,000 GHz (at 5.7 GHz) and tau(f) = +48 ppm/degrees C.