New microwave dielectric ceramics based on the CaRNbWO8 (R = Y, La, Ce, Nd or Sm) system

Microwave dielectric ceramics are the key materials utilized in microwave band communication. With the broadening of the operative frequency of 5G communication devices, it’s vital to boost the dielectric properties and frequency selectivity of microwave dielectric ceramics. Here, new microwave dielectric ceramics based on the Ca–R–Nb–W–O (R = Y, La, Ce, Nd or Sm) have been successfully fabricated by traditional solid-state reaction method, and also the effects of different rare-earth ion on their structure and dielectric properties have been systematically investigated. The structure of all the ceramics is assigned to the scheelite CaWO₄ phase, indicating that the change of R-site ions does not change the crystal structure. The ceramics have a highly relative density ranging from 93 to 99%. The main factor affecting the dielectric parameters is the ion polarization, while densities and hopping conductivity between Ce³⁺ and Ce⁴⁺, Sm³⁺ and Sm²⁺ ions also have an effect. The Nyquist plots of the prepared ceramic samples all show single semi-circlar, which are caused by the grain boundary impedance. The prepared ceramics have excellent dielectric properties in a wide range of frequencies (0–1 MHz) for satisfying the development requirements of communication technology.