Structural and dielectric studies for the conduction mechanism analyses of lithium-niobate oxide ferroelectric ceramics

Ferroelectric ceramic samples of lithium-niobate (LiNbO3) material synthesized by solid-state reaction were investigated. Raman spectra analysis confirmed that the structure of these ceramics became more rigid with the rise of Li composition. Frequency and temperature dependencies of dielectric permittivity and electric modulus of these ceramics were studied in the ranges of frequency 1 Hz - 10 MHz and temperature 300-1000 degrees C, respectively. We found that both dielectric constant epsilon' and loss epsilon '' are high at lower frequencies and decrease with increasing of frequency. Furthermore, the electric modulus analyses reveal a non-Debye relaxation behavior and the shift in relaxation peak towards higher frequency range indicates a specific conduction process in the material and favoring of long-range motion of mobile charge carriers. Relaxation frequency extracted using imaginary part M '' and dc conductivity measurements were found to follow the Arrhenius law, which indicate that the conduction process is thermally activated.