Investigation on structure and microwave dielectric properties of novel high dielectric constant Ca(1−3x/2)CexTiO3 ceramics sintered in nitrogen atmosphere

Ca(1−3x/2)CexTiO3 (0 ≤ x ≤ 0.40, CCT) ceramics were prepared in nitrogen atmosphere using the conventional solid-state reaction method. The XRD, Raman spectra and XPS were employed to investigate the relationship between the structure and microwave dielectric properties of CCT ceramics. XRD results and Raman spectra analysis indicated that all the samples were the perovskite structure and a transition from Pbnm to I4/mcm at x = 0.16 was observed. The SEM micrographs showed the average grain size increased with x and dense structures were achieved at x ≥ 0.1, but abnormal grain growth occurred at x ≥ 0.16. With the increase of cerium addition, both the dielectric constant (εr) and Q × f value increased at first and then decreased, while temperature coefficient of resonator frequency (τf) decreased monotonously from 575 to 295 ppm/°C. The substitution of Ce in A-site restrained the reduction of Ti4+ ions and enhanced the oxygen octahedral distortion. For the Ca0.79Ce0.14TiO3 ceramics, a high Q × f value (~ 11705 GHz) in addition to the high dielectric constant (εr = 130.6), was exhibited which was suitable for integration and miniaturization of microwave component.