Structural characterization and electrical properties of sintered magnesium–titanate ceramics

In this article the influence of ball miling process on structure of MgO–TiO2 system, as well as the electrical properties of samples after sintering, was investigated. The mixtures of MgO–TiO2 powders were mechanically activated in a planetary ball mill for the time period from 0 to 120 min. The influence of mechanical activation and sintering on the lattice vibrational spectra was studied by Raman spectroscopy at room temperature. Structural investigations have been performed on produced powders. Nitrogen adsorption method was used to determine the BET specific surface area and pore size distribution. Unusual results have been obtained: specific surface area continuously decreased up to 40 min of activation and increased after that, reaching its minimum value of 5.5 m2/g. The Raman spectra of activated powders have shown that anatase modes have been decreasing in intensity and broadening as the time of activation extended. Also, the additional modes attributed to TiO2 II, srilankite and rutile phases started to appear as a consequence of activation. The small differences noticed in the Raman spectra of sintered samples have been explained by structural modification of MgTiO3 phase due to the presence of defects.The effects of activation and sintering process on microstructure were investigated by scanning electron microscopy (SEM). The electrical measurements showed difference in dielectric constant (εr), loss tangent (tg δ) and specific resistance (ρ) as a function of time of mechanical treatment.

The Raman spectra of the saples obtained by sintering non-milled and milled powders at 1300 °C are shown in Fig. 5. During the treatment at a higher temperature, two phased system (MgTiO3 and Mg2TiO4) is formed [23]. According to the factor group analyses, MgTiO3 there are 10 Raman active modes 5Ag + 5Eg, whereas spinel Mg2TiO4 has five ones (A1g + Eg + 3F2g).Figure optionsDownload as PowerPoint slideHighlights
► The influence of ball milling on the structure of MgO–TiO2 system was studied.
► Influence on electrical properties of sintered samples was investigated also.
► Raman spectroscopy pointed out phase transition of titanates.
► SEM showed structural modifications depending on duration of MA.
► MA and sintering can improve the properties of sintered MT ceramics.