Electrical Investigations of Aurivillius Type Sr_0.7A_0.3Bi₂Nb₂O₉ (A = Ca, La and Pb) Ferroelectric Ceramics

Abstract

Aurivillius type bismuth layer structured ferroelectrics (BLSF) have been found to possess strong relationship between tetragonal strain (c/a) and extrinsic/ intrinsic conductivity. The extrinsic part of the conductivity is known to depend upon space charge in the sample. The present paper discusses effects of 30 atomic % doping of Ca, La and Pb on tetragonal strain, conductivity and dielectric constant/loss with temperature and frequency. Tetragonal strain increases on doping calcium and lead while it shows a decrease on doping lanthanum. The calcium and lanthanum doped samples show pronounced space charge part of dielectric constant while lead doped sample shows nearly constant permittivity values. No phase transition is observed in the calcium doped sample up to 600°C while for the lanthanum doped sample a decrease of 141°C is observed in the value of Curie temperature compared to that for the undoped sample.

Keywords:

• Tetragonal strain
• x-ray diffractograms
• dielectric constant
• dielectric loss