Effects of ion polarizability and oxygen vacancy on microwave dielectric properties of fluorite-structured Ce1−xCaxO2−x

X-ray diffractometer with Rietveld refinement and Raman spectroscopy were used for phase analysis. Ca doping results in decreased ε r (24.09–21.52), Q × f (68 914–40 110 GHz), and τ f (−50.0 ppm/°C to −60.2 ppm/°C) all decrease, which obviously does not conform to the mutual constraint relationship among the three parameters of microwave dielectric properties. The ε r of Ce 1− x Ca x O 2− x ceramics is affected by the ion polarizability and the Ce rattling and valence states, among which the rattling of Ce cations plays a dominant role. The presence of oxygen vacancies in Ce 1− x Ca x O 2− x ceramics explains the decrease in Q × f . The τ ε , ε r , and α L are responsible for the decrease in τ f , especially for the τ αm -3 α L values.