Influence of Ge4+ substitution for Zr4+ on the microwave dielectric properties of Mg(Zr1-xGex)Nb2O8 (0 ≤ x ≤ 0.4) ceramics

Dense Mg(Zr1-xGex)Nb2O8 (x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were successfully synthesized through traditional solid state reaction route. The relations between microstructure and microwave dielectric properties were studied. The formation of single MgZrNb2O8 phase with the monoclinic wolframite structure was verified by XRD patterns. Experimental dielectric constant was found to be closely related to bond polarizability, and theoretical dielectric constant calculated based on P-V-L theory shows the same tendency with the experimental dielectric constant when the substitution amount of Ge4+ changes. The increase in Q x f and |tau(f)| were mainly attributed to the increase in packing fraction and the Nb-site bond valence, respectively. Excellent dielectric properties were obtained for Mg(Zr1-xGex)Nb2O8 (x = 0.2) ceramic sintered at 1300 degrees C for 4 h: epsilon(r)= 24.26, Q x f = 80,492.8 GHz, tau(f) = -51.95 ppm/degrees C.