Microwave Dielectric Characteristics of Ilmenite-Type Titanates with High Q Values

The microwave dielectric characteristics of ilmenite titanates, M 2+ TiO 3 (where M 2+ =Ni, Mg and Mn) and ( Mg 0.95 M 0.05 2+ )TiO 3 (where M 2+ = Ni, Mg, Co and Mn) series, have been investigated as a function of ionic radius of M 2+ and (Mg 0.95 M 0.05 2+ ) 2+ ions, respectively. The ilmenite titanates have high Q value and low dielectric constant due to the isolation of TiO 6 octahedra by the M O 6 octahedron layer and cation vacancy layer in comparison with the perovskite titanates. The existence of localized 3 d electrons in Ni 2+ (3 d 8 ) and Mn 2+ (3 d 5 ) is concerned with the microwave dielectric properties of the M 2+ TiO 3 series. The dielectric constant ε r at 10 GHz of the (Mg 0.95 M 0.05 2+ )TiO 3 series shows the minimum value around the average ionic radius of 0.721 Å, while the Q value shows a maximum, probably due to a local lattice distortion. The (Mg 0.95 Co 0.05 )TiO 3 compound shows a maximum Q value of 23,000 at 10 GHz, dielectric constant of 16.8, and τ f of -54 ppm/K.