Ultra‐high Quality Factor of (Zn 2/3 Nb 1/3 ) 3+ Co‐substitution MgAl 2 O 4 Microwave Dielectric Ceramics

Herein, nominal compositions of MgAl 2– x (Zn 2/3 Nb 1/3 ) x O 4 ( x = 0.00, 0.04, 0.08, 0.12, 0.16, 0.20, 0.30, 0.40, and 0.50) ceramics are synthesized using a solid‐phase reaction method. The (Mg/Zn)Al 2 O 4 solid solution and second‐phase Mg 4 Nb 2 O 9 greatly improve the microwave dielectric properties of the samples. Moreover, the second phase, ionic polarizability, and relative density affect the dielectric constant ( ε r ) value. The quality factor (Qf) value is correlated with the packing fraction, achieving a maximum value of ≈563 000 GHz at x = 0.40. The temperature coefficient of the resonant frequency ( τ f ) value is negatively correlated with the B‐site bond value. When x = 0.40, the nominal composition MgAl 1.6 (Zn 2/3 Nb 1/3 ) 0.4 O 4 ceramic exhibits good microwave dielectric properties: ε r = 9.06, ultrahigh Qf = 563 000 GHz, and τ f = –45 ppm °C −1 .