Correlation of crystal structure and microwave dielectric properties of Nd1.02(Nb1−xTax)0.988O4 ceramic

Abstract

The phase structures of Nd_1.02(Nb_1−xTa_x)_0.988O₄ ceramics were analyzed via multiphase structure refinement. The X-ray diffraction patterns of Nd_1.02(Nb_1−xTa_x)_0.988O₄ showed that the monoclinic fergusonite structure of NdNbO₄ and a second phase NdTa₇O₁₉ were obtained. The oxygen octahedron distortion was investigated according to the supercell of the NdNbO₄ ceramic. The correlations between packing fractions, bond valences and microwave dielectric properties were discussed. For the main phase NdNbO₄, as the polarizabilities increased, the ε increased. The Q × f value was mainly attributed to the packing fraction. With the increase of bond valence of the B-site and the oxygen octahedron distortion, the τ_f value decreased. The substitution of Ta⁵⁺ for Nb⁵⁺ effectively influenced the microstructure and the microwave dielectric properties of NdNbO₄ ceramics. Optimal microwave dielectric properties can be obtained for Nd_1.02(Nb_0.94Ta₀.₀₆)_0.988O₄ ceramics at x = 0.06.