Study of the microwave dielectric properties of (La 1− x Sm x )NbO 4 ( x =0‐0.10) ceramics via bond valence and packing fraction

The (La 1− x Sm x )NbO 4 ( x =0‐0.10) ceramics were prepared by the conventional solid‐state reaction method. The microstructure and the microwave dielectric properties were discussed in detail. The X‐ray diffraction patterns of (La 1− x Sm x )NbO 4 ( x =0‐0.10) showed that only a single monoclinic fergusonite structure of LaNbO 4 could be found. The dielectric constant (ε r ) was affected by the dielectric polarizabilities and the B‐site bond valence. The variation trend of Q × f 0 was in accordance with packing fraction. The temperature coefficient of resonant frequency (τ f ) had a close relationship with the B‐site bond valence, which was determined by the bond strength and bond length. When sintered at 1325°C for 4 hours, the (La 1− x Sm x )NbO 4 ceramics with x =0.08 exhibited enhanced microwave dielectric properties: ε r =19.37, Q × f 0 =62203 GHz and τ f =2.57 ppm/°C. In addition, we made an overview about the ceramics that possess the same packing fraction and bond valence relationships, the results show that this structure‐property relationship has a wide applicability.