The Structure and Microwave Dielectric Properties of MgTi[sub.1−x]Ix/IO[sub.3] Ceramics

MgTi[sub.1−x] (Mn[sub.1/3] Nb[sub.2/3] )xO[sub.3] (x = 0–0.30) ceramics were prepared via the solid-state reaction method. The phase composition, microstructure, bond characteristics, and microwave dielectric properties of MgTi[sub.1−x] (Mn[sub.1/3] Nb[sub.2/3] )xO[sub.3] (x = 0–0.30) were systematically investigated. The MgTi[sub.1−x] (Mn[sub.1/3] Nb[sub.2/3] )xO[sub.3] ceramics presented an ilmenite type with an R-3 space group, and the secondary-phase MgTi[sub.2] O[sub.5] only existed at x = 0 and 0.30. The introduction of (Mn[sub.1/3] Nb[sub.2/3] )[sup.4+] effectively suppressed the formation of the MgTi[sub.2] O[sub.5] phase. The variation trend of the dielectric constant (εr) was the same as relative density. The quality factor (Qf) value was enhanced by the stable microstructure, which was caused via the lattice energy of Ti/(Mn[sub.1/3] Nb[sub.2/3] )-O bonds. And a high Qf value (353,000 GHz) was obtained for MgTi[sub.1−x] (Mn[sub.1/3] Nb[sub.2/3] )xO[sub.3] (x = 0.04) ceramics sintered at 1250 °C. In addition, the introduction of Mn[sup.2+] ions with a larger ionic radius exacerbates the distortion of TiO[sub.6] octahedra, leading to significant fluctuations in the temperature coefficient of the resonance frequency (τf) value.