Crystal structure, densification, and microwave dielectric properties of Li 3 Mg 2 (Nb (1− x ) Mo x )O 6+ x /2 (0 ≤ x ≤ 0.08) ceramics

A novel system Li 3 Mg 2 (Nb (1− x ) Mo x )O 6+ x /2 (0 ≤  x  ≤ 0.08) microwave dielectric ceramics were fabricated by the solid‐state method. The charge compensation of Mo 6+ ions substitution for Nb 5+ ions was performed by introducing oxygen ions. The X‐ray diffraction patterns and Rietveld refinements indicated Li 3 Mg 2 (Nb (1− x ) Mo x )O 6+ x /2 ceramics with single phase and orthorhombic structure. Micro‐structure and density confirmed that the grain of Li 3 Mg 2 (Nb (1‐ x ) Mo x )O 6+ x /2 ceramics grew well. In addition, the permittivity of Li 3 Mg 2 (Nb (1− x ) Mo x )O 6+ x /2 ceramics with the same trend as density decreased slightly with increasing Mo 6+ ions content. However, the Q*f and τ f were obviously improved with an appropriate amount of Mo 6+ ions. When x  ≤ 0.04, the Q*f was closely related to the bond valence of samples, while when x  ≥ 0.06, the Q*f was closely related to the density of samples. The variations of τ f and oxygen octahedral distortion were the opposite. In conclusions, the Li 3 Mg 2 (Nb 0.98 Mo 0.02 )O 6.01 ceramic sintered at 1200°C for 6 hours exhibited outstanding properties: ε r  ~ 15.18, Q*f  ~ 116 266 GHz, τ f  ~ −15.71 ppm/ o C.