Microwave dielectric properties of MgTiO3-based ceramics

Effects of the partial substitution of divalent and/or tetravalent cations for Mg2+ and/or Ti4+ on the structural characteristics and dielectric properties of MgTiO3-based ceramics [MgTiO3 (MT), (Mg0.95Zn0.05)TiO3 (MZT), Mg(Ti0.95Sn0.05)O3 (MTS), (Mg0.95Zn0.05)(Ti0.95Sn0.05)O3 (MZTS)] were investigated at microwave frequencies. Among these MgTiO3-based ceramics with single-phase ilmenite structure, the MZTS showed the largest unit cell volume owing to the larger ionic radii of Sn4+ (0.69 Å) and Zn2+ (0.74 Å) in comparison to Ti4+ (0.605 Å) and Mg2+ (0.72 Å), respectively. The quality factor (Qf) of the MZTS showed the highest value among all the MgTiO3-based ceramics investigated; this is because of the strong bond strength at the Ti site, confirmed by Raman spectroscopy analysis and the high average covalency originated from the small difference in electronegativity between the cation and oxygen ion in the oxygen octahedra. The dielectric constant (K) of MgTiO3-based ceramics was affected by the dielectric polarizability of the composing ions. The relationship between the microstructure and microwave dielectric properties was also discussed.