Novel (1-x)MgCu2Nb2O8 − xTiO2 composite ceramics with high Q×f and near-zero τ f

For the MCu2Nb2O8 (M=Ca, Mg, Zn or Ni) composite ceramics, it is still a difficult problem to achieve both high Q×f valule and near-zero temperature coefficient of resonant frequency (τf). In this paper, the (1-x)MgCu2Nb2O8 − xTiO2 (0 ≤ x ≤ 0.28) ceramics were fabricated by the two-step sintering (TSS) technique. Results of x-ray diffraction (XRD) and Raman spectroscopy proved that the ceramic samples were composite phases of MgNb2O6, CuO and TiO2. The chemical compositions and valences of Mg, Cu, Nb, O and Ti were investigated by x-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) showed that proper TiO2 addition could promote growth of grains and increase the average grain size. Appropriate TiO2 content and enhanced densification contributed to the 0.84MgCu2Nb2O8 − 0.16TiO2 ceramics sintered at 935 °C with εr = 18.75, Q×f = 34,398 GHz (f0 = 7.8 GHz), and τf = −0.56 ppm/°C, exhibiting potential applications in Low Temperature Co-fired Ceramic (LTCC) devices.