Low-temperature sintered Zn2SiO4-CaTiO3 ceramics with near-zero temperature coefficient of resonant frequency

The microwave dielectric properties and the microstructures of (1 - x) Zn2SiO4-xCaTiO(3) composite ceramics with Li2CO3-H3BO3 additives prepared by solid-state reaction method have been investigated. The crystalline phases were studied systematically by using the X-ray diffraction (XRD), microstructures by the scanning electron microscopy (SEM) and composition analysis by energy-dispersive spectroscopy (EDS). The tau(f) of (1 - x) Zn2SiO4-xCaTiO(3) was found to be dependent on phase constitution, which is related to the amount of CaTiO3. When x = 0.05, the tau(f) of (1 - x) Zn2SiO4-xCaTiO(3) was near 0 ppm/degrees C. The microwave dielectric properties of 0.95Zn(2)SiO(4)-0.05CaTiO(3) ceramics samples with Li2CO3-H3BO3 additives sintered at 900-1000 degrees C were characterized, and the results indicated that the permittivity and Q x f were associated with the amount of Li2CO3-H3BO3 and the sintering temperature. The sintering temperature of ceramics was effectively reduced to 950 degrees C from about 1250 degrees C and the temperature coefficient of resonant frequency (tau(f)) was modified to -4.5 ppm/degrees C with good Q x f. The addition of 4.0 wt% Li2CO3-H3BO3 in 0.95Zn(2)SiO(4)-0.05CaTiO(3) ceramics sintered at 950 degrees C showed excellent dielectric properties of epsilon(r) = 7.1, Q x f = 26,300 GHz (f = 7.1 GHz) and tau(f) = -4.5 ppm/degrees C. Moreover, this material has a chemical compatibility with silver, making it a very promising candidate material for LTCC applications. (C) 2011 Published by Elsevier B. V.