Dielectric relaxation in LiNbO3-MgAl2O4 nanocomposite

LiNbO3-MgAl2O4 nanocomposite was synthesized by a modified sol-gel and long-time sintering process. X-ray diffraction patterns reveal the presence of a rhombohedral structure LiNbO3 and a cubic structure MgAl2O4. The average grain sizes were calculated. Consistent with the XRD results, HRTEM image shows the distribution of the two phases at the nanoscale. The dielectric constant and dielectric loss are determined as functions of temperature over a wide range of frequencies from 10 Hz to 10 kHz. The dielectric loss spectrum displays a strong dispersion at temperatures 300-390 K. The activation energy was calculated by fitting the loss-peak frequencies using the Arrhenius law. The determined value of 0.34 eV is close to the value of that for Li diffusion in nanocrystalline LNO. It is thus believed that the dielectric relaxation in the nanocomposite could be attributed to the Li diffusion in LNO. (C) 2012 Elsevier B.V. All rights reserved.