Electrical anisotropy in the hot-forged CaBi4Ti4O15 ceramics

Textured CaBi4Ti4O15 (CBT) ceramics have been fabricated via a hot-forging technique. The effect of grain orientation on the dielectric and electrical properties is studied by impedance (Z(*)) and modulus (M-*) spectroscopy. The degree of orientation (F) calculated from X-ray diffraction pattern is found to be 89.4% along the c-axis of the crystal structure. The permittivity was measured along both perpendicular and parallel directions of the forging axis. The ratio of permittivity along perpendicular to parallel direction is found to be similar to 3 at the Curie temperature of 797 degrees C. The non-superimposition of the normalized Z '' and W vs. frequency plot revealed the conduction in the material is localized and deviate from ideal Debye behavior. The power law exponent n of the material has been explained on the basis of jump relaxation model and revealed the conduction through grain boundary. Activation energy (E.) is obtained from Arrhenius plots of the dc conductivity for both the ceramics and it is found to be 0.89 eV and 0.78 eV for CBT (parallel to) and CBT (perpendicular to), respectively. (C) 2009 Elsevier Masson SAS. All rights reserved.