DIELECTRIC-SPECTROSCOPY OF MGTIO3-BASED CERAMICS IN THE 10(9)-10(14) HZ REGION

Magnesium titanate (MgTiO3) powder was prepared by a chemical route (Pechini method) and different dopants were added to prepare several compositions. These pure and doped compositions were sintered in air and dense ceramics were obtained. The pure MgTiO3 samples were also subjected to different heat treatments during sintering. Complex permittivity spectra of ceramic samples were determined by various techniques in the 10(9)-10(14) Hz range. These techniques included infrared spectroscopy in transmission and reflectivity modes and microwave dielectric measurements. Extrapolation to microwave frequencies from infrared data, according to the proportionality epsilon''(nu) is-perpendicular-to nu, agrees quite well with the microwave data measured at 8 GHz and it is a useful procedure to estimate intrinsic microwave losses. Fast cooling from high temperatures of MgTiO3 samples increased dielectric loss, probably due to a structural disorder. Dopants have two types of effect depending on whether they form a distinct second phase or a solid solution with MgTiO3. In this last case intrinsic losses are strongly affected.