Correlation between crystal structure and modified microwave dielectric characteristics of Cu2+ substituted Li3Mg2NbO6 ceramics

Abstract Structural characteristics exert significant influences on microwave dielectric properties, and ion substitution is widely adopted to modify material performances by adjusting the crystal structure. In this work, low loss Li 3 Mg 2-x Cu x NbO 6 ( x  = 0–0.04) ceramics were prepared by Cu 2+ substitution. The impacts of Cu 2+ substitution for Mg 2+ sites on the microwave dielectric characteristics and crystal structure were discussed in detail. Rietveld refinement results implied that a single Li 3 Mg 2 NbO 6 phase was formed. Additionally, a dense and homogeneous microstructure with grain sizes of 7–9 μm could be achieved, and moderate Cu 2+ substitution could significantly promote the grain growth. The correlation between microwave dielectric characteristics and crystal structure was discussed by calculating some structural parameters. The e r was determined by the polarizability. The Q × f was influenced by the packing fraction. The τ f value was dependent on the NbO 6 octahedron distortion, and the τ f value could be adjusted to near zero for x = 0.02. Typically, the Li 3 Mg 2-x Cu x NbO 6 (x = 0.02) composition exhibited remarkable microwave dielectric performances: e r  = 15.75, Q × f  = 92,134 GHz (9.86 GHz) and τ f  = −2 ppm/°C, making it a promising candidate for temperature-stable millimeter-wave applications.