Colossal permittivity and low dielectric loss of LaAl0.67-xCaxMn0.33O3 ceramics

Abstract

The exploration of colossal dielectric permittivity materials with low dielectric loss in a wide range of frequencies continues to attract considerable interest. The compounds with a colossal dielectric permittivity have attracted a lot of attention because of their applications in high-energy density storage and microelectronics as a result of the continually increasing demands of microelectronics applications. Ca and Mn co-doped LaAl0.67-xCaxMn0.33O3 (x = 0.00, 0.02, 0.04, 0.05) ceramics were prepared by a solid-state reaction method. Pellet shaped samples prepared from each composition were sintered at 1723 K for 5 h. X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) are used to carry out the structural and surface morphology analyses. The dielectric constant (ɛʹ), dielectric loss (tanδE), ac-conductivity (σac) and complex impedance spectra analysis of the LaAl0.67-xCaxMn0.33O3 ceramics were studied in detail. Colossal permittivity up to 103 was obtained across the frequency range up to 106 Hz. The impedance analysis of the co-doped LaAlO3 ceramics indicated that the colossal permittivity phenomenon has been explained by the Koops theory based on Maxwell–Wagner model. The values of (tanδE) sharply decreas as frequency increases in the low frequency region. While in the high frequency region, tanδE increases with the increase in frequency. However, in the intermediate frequencies, the values of tanδE are minimum which indicates that the compositions are of good quality material in this range. A high precision impedance analyzer has been also used to study the frequency dependent initial permeability.