Improvements in the sintering behavior and microwave dielectric properties of fergusonite-type NdNbO4 ceramics

Microwave dielectric ceramics based on fergusonite-type NdNbO4 were prepared by an aqueous sol–gel process. The precursor powders and dielectric ceramics were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and microwave methods. Highly reactive nano-sized magnesium titanate powders with particle sizes of 20–40 nm were successfully obtained at 900 °C as precursors. The sintering characteristics and microwave dielectric properties of NdNbO4 ceramics were studied depending on sintering temperatures ranging from 950 °C to 1300 °C. With the increase of sintering temperature, density, εr and Qƒ values increased and saturated at 1150 °C with excellent microwave properties of εr=29.8, Qƒ=49,010 GHz and τƒ=53 ppm/°C. The correlations of microstructure and dielectric properties for NdNbO4 ceramics were also investigated.