Modification of NdNbO ₄ microwave dielectric ceramic by Bi substitutions

In the present work, Bi 3+ was used to substitute for Nd 3+ in the NdNbO 4 ceramic and pure fergusonite solid solution was formed within 20 mol. % substitutions. Microwave dielectric permittivity of the (Nd 1‐ x B i x )NbO 4 (x ≤ 0.2) ceramics increased linearly with x value due to the larger ionic polarizability of Bi 3+ than Nd 3+ . Excellent microwave dielectric properties with a permittivity ( ε r ) ~22.5, a Qf (Q = quality factor, f = resonant frequency) ~50 000 GH z, and a TCF ~−9 ppm/°C were obtained in the (Nd 0.9 Bi 0.1 )NbO 4 ceramic. This method might work in other fergusonite‐type rare‐earth ortho‐niobates.