AC response of Bi-modified Pb_0.92La_0.08(Zr_0.65Ti_0.35)_0.98O₃ ceramics

¹ Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur – 721302, India
² Department of Aerospace Engineering, Indian Institute of Technology, Kharagpur – 721302, India

Corresponding author: dutta_som@yahoo.co.in

Received: 28 October 2005
Revised: 1 June 2006
Accepted: 21 June 2006
Published online: 11 October 2006

Abstract

Polycrystalline electroceramics have been prepared by varying modifier to former (Bi/La) ratios () according to the complex formula Pb_0.92[LaBi_z] _0.08[Zr_0.65Ti_0.35] _0.98O₃ (PLBZT), where z = 0.0, 0.3, 0.6. The electrical properties of PLBZT compounds were studied using the ac impedance spectroscopy technique over a wide range of temperature (30–500 °C) in the frequency range of 100 Hz–1 MHz. Nyquist plots recorded at different temperatures show a decrease in the bulk resistance (R_b) with rise in temperature for PLZT material (z = 0.0) i.e., NTCR behavior like semiconductors. The Nyquist plots also indicates that the bulk resistance of the material has been observed to be concentration dependent and decreased in two order of magnitude with higher Bi-addition in PLZT matrix. Bismuth (Bi) substitution at the lanthanum (La) position not only resulted in lowering of the electrical resistance with its higher concentration but also has changed the NTCR behavior of PLZT (z = 0.0) to PTCR (positive temperature coefficient of resistance) for PLBZT. Electrical property studied by complex impedance spectroscopic method also indicates the evidence of (i) single electrical relaxation attributed to the presence of bulk contribution to the electrical properties, (ii) presence of temperature dependent electrical relaxation phenomenon and (i) diminution in the barrier to the mobility of charge carrier on Bi-substitution.