Search

The role of mixed-valence structure in colossal dielectric constant ( CDC) behavior has been investigated in LaFeO3 ceramics by tuning the ratio of Fe2+/Fe3+ through substituting Al for Fe. The ratio of Fe2+/Fe3+ is decreased gradually from 1.0 to 0.0 by increasing the concentration of Al3+. Two clear-cut correlations have been found: (i) the relationship between the CDC behavior and the ratio of Fe2+/Fe3+ follows an exponential function and (ii) the activation energy of the polaron relaxation is proportional to [ABSTRACT FROM AUTHOR]

By means of dielectric permittivity, electric modulus and impedance, the dielectric properties of LiF single crystals were investigated in the temperature range of 30°C-800°C and frequency range of 50 Hz-10 MHz. Two thermally activated relaxations, R1 and R2, were observed. The relaxation R1 showing activation energy around 0.8 eV was found to be related to the Li-ion diffusion in the crystal. The relaxation R2 contains three Arrhenius segments, the low-, mid-, and high-T segments, separated by boundary temperatures of 325°C and 425°C. These segments in the order of ascending temperature were found to be associated with F3, F3+ centers, F2 centers, and F centers, respectively. [ABSTRACT FROM AUTHOR]

The role of mixed-valence structure in colossal dielectric constant ( CDC) behavior has been investigated in LaFeO3 ceramics by tuning the ratio of Fe2+/Fe3+ through substituting Al for Fe. The ratio of Fe2+/Fe3+ is decreased gradually from 1.0 to 0.0 by increasing the concentration of Al3+. Two clear-cut correlations have been found: (i) the relationship between the CDC behavior and the ratio of Fe2+/Fe3+ follows an exponential function and (ii) the activation energy of the polaron relaxation is proportional to [ABSTRACT FROM AUTHOR]