Correlation of structure and dielectric response in Ce-doped double perovskite cobaltite

Abstract

Double perovskite Bi2Ca2-xCexCoO6; x = 0.00, 0.05, 0.10 and 0.15 (BCCCO) is synthesized by co-precipitation route. X-ray diffraction (XRD) confirms the monoclinic single-phase crystal structure with negligible variation in unit cell parameters, indicating that the Cerium (Ce) has been successfully incorporated. With Ce doping, the average crystallite size of Bi2Ca2CoO6 (BCCO) nanoparticles decreases. Scherrer's formula was used to determine the crystallite sizes (33–37 nm) of BCCO nanoparticles. Jonscher's power law is used to investigate the conduction mechanism of all the prepared specimens. The power-law specifies the correlated barrier hopping for BCCCO x = 0.00 and 0.05, short polaron tunneling for x = 0.10, while BCCCO x = 0.15 follows overlapping large polaron tunneling. The dielectric permittivity has been calculated with a frequency range of 20 Hz - 3 MHz, and the Ce doped samples show a high value of dielectric permittivity εr = 1.79 × 105 at 500 °C. The influence of crystallite size on the dielectric permittivity of BCCCO was examined in this work. The relaxation time and spreading factor of all samples are investigated using Non-linear Debye's function. All these features are studied as a function of frequency at temperatures ranging from 100 to 500 °C. Here, the DC electrical conductivity of BCCCO is investigated by the four-probe method at 50–400 °C. In Ce-doped specimen the lowest value of thermal conductivity (k = 0.797 W/m-K at 120 °C) has been observed.