Microwave dielectric properties of Mg2Ti1-x(Ni1/3Sb2/3)(x)O-4 ceramics

Dependence of the dielectric properties of Mg2Ti1-x(Ni1/3Sb2/3)(x)O-4 (0.025 <= x <= 0.1) on structural characteristics were investigated at microwave frequencies. For the specimens sintered at 1450 degrees C for 4 h (single-step sintering), the quality factor (Qf) initially increased with increasing (Ni1/3Sb2/3)(4+) content (x) up to x = 0.05, and then decreased. Highest Qf value (182,270 GHz) was obtained for the specimen with x = 0.05 sintered through two-step sintering (1450 degrees C, 10 min followed by 1400 degrees C, 4 h) owing to its high densification and homogenous microstructure. The quality factor (Qf) depends on relative density and bond valence which is dependent on the bond strength and length between oxygen ions and cations in the oxygen octahedron of the crystal structure. The highest bond strength was also confirmed for specimens with x = 0.05 based on shifts in the peak position and full width at half maximum of the Raman mode. Overall, Mg2Ti0.95(Ni1/3Sb2/3)(0.05)O-4 ceramics showed high Qf (=182,270 GHz), appropriate K(=14.13) and adjustable TCF(=-48.2 ppm/degrees C), which are applicable to telecommunication systems and the integration of devices at microwave frequencies.