Microwave dielectric properties of a new ceramic system NdNbO₄ with CaF₂ addition

Abstract

Microwave dielectric ceramics NdNbO₄ were prepared by conventional mixed oxide route. The effects of CaF₂ addition on the microstructures and microwave dielectric properties of NdNbO₄ ceramics were investigated systematically. Formation of second phase NdNb₃O₉ and CaNb₂O₆ can be detected at 0–1.0 wt.% CaF₂ additions and 2.0 wt.% CaF₂ additions, respectively. Variation of grain shapes were observed with CaF₂ content increasing. The microwave dielectric properties were affected by the amount of CaF₂ addition. At 1225 °C for 4 h, NdNbO₄ ceramics with 2.0 wt.% CaF₂ possesses excellent microwave dielectric properties: ε_r = 20.1, a Q × ƒ = 75000 GHz and τ_ƒ = −19.16 ppm/°C. There was more than two times increase in quality factor with 2.0 wt.% CaF₂ doping in NdNbO₄ ceramics.