Abstract

• A facile transition metal Fe doping has been employed as an effective approach to alter the electrical and optical properties of LaCoO3. The aim of the research work is to study the effect of sintering temperature on structure, electrical and optical properties of the nanocrystalline ceramics. LaCo0.6Fe0.4O3 nanocrystalline ceramics was prepared from constituent metal nitrates, citric acid and ethylene glycol by sol-gel method and sintered at different temperatures. The LaCo0.6Fe0.4O3 powder calcined at 600 ºC were made circular pellets. The pellets were sintered at 800 ºC, 900 ºC and 1000 ºC. The obtained ceramic pellet samples were characterized by X-Ray Diffractometer (XRD), Fourier Transform Infra-Red (FT IR) spectrometer and Scanning Electron Microscopy (SEM). The XRD results show all LaCo0.6Fe0.4O3 samples have hexagonal crystalline structure with R-3c space group and show single phase. The average crystallite size of the pellet samples varied from 20 to 40 nm due to the growth of nanocrystals at higher temperatures. The respective metaloxygen stretching vibrations of the prepared samples were observed in FT IR spectra. Surface morphology of the prepared ceramics were studied by SEM. The optical properties of LaCo0.6Fe0.4O3 ceramic samples were studied from UV-visible spectrophotometer and the optical band gaps were also estimated by using Tauc’s relation. The band gap values of the pellet samples were 2.2 eV, 2.1 eV and 2.0 eV, respectively and these values were within semiconductor band-gap range. The ac conductivities and dielectric properties were studied by LCR meter in the frequency range of 1MHz - 2MHz. The experimental results indicated that the dielectric loss factor (tan δ), dielectric constant (εˊ), ac conductivity (σac), resistivity (ρ) and dc conductivity (σdc) were found to depend on the frequency.