Development of Electronic and Electrical Materials from Indian Ilmenite

Some new complex electronic materials have been prepared by mixing bismuth oxide (Bi2O3) and ilmenite in different proportions by weight, using a mixed-oxide technique. Room-temperature x-ray diffraction analysis confirms the formation of a new compound with trigonal (rhombohedral) crystal structure with some secondary phases. Studies of dielectric parameters (epsilon (r) and tan delta) of these compounds as a function of temperature at different frequencies show that they are almost temperature independent in the low-temperature range. They possess high dielectric constant and relatively small tangent loss even in the high-temperature range. Detailed studies of impedance and related parameters show that the electrical properties of these materials are strongly dependent on temperature, showing good correlation with their microstructures. The bulk resistance, evaluated from complex impedance spectra, is found to decrease with increasing temperature. Thus, these materials show negative temperature coefficient of resistance (NTCR)-type behavior similar to that of semiconductors. The same has also been observed from their I-V characteristics. Complex electric modulus analysis indicates the possibility of a hopping conduction mechanism in these systems with nonexponential-type conductivity relaxation. The nature of the variation of the direct-current (dc) conductivity with temperature confirms the Arrhenius behavior of these materials. The alternating-current (ac) conductivity spectra show a typical signature of an ionic conducting system, and are found to obey Jonscher's universal power law.