Processing and dielectric properties of La(Mg0.5Ti0.5)O3-BaTiO3 ceramics

(1-x)La(Mg0.5Ti0.5)O-3-xBaTiO(3) (0less than or equal toxless than or equal to0.7) perovskite ceramics have been prepared by a chemical method and their permittivity and dielectric loss have been studied over a wide frequency range. The far infrared complex dielectric function has been evaluated from reflectivity data and extrapolated towards the microwave range. For the compositions with x=0 and 0.1, both the measured at microwave range and extrapolated values were found to be in good agreement, revealing that microwave losses are essentially intrinsic and due to lattice contributions. For solid solutions with higher BaTiO3 content, the results suggest that additional contributions are present. The analysis of the temperature dependence of the low frequency permittivity indicates that a possible additional mechanism may be ionic conduction. The comparison of the dielectric behaviour observed in ceramics sintered in oxygen and air suggests that the oxygen vacancies due to the reducing of Ti4+ seems to play an important role in the onset of the ionic conduction.