Influence of lanthanum doping on the dielectric, ferroelectric and relaxor behaviour of barium bismuth titanate ceramics

• Published in: Journal of physics. D, Applied physics Vol. 42; no. 7; pp. 075405 - 075405 (9); [np]
• Main Authors: Kumar, Sunil, Varma, K B R
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 07.04.2009; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric loss and relaxation; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Domain structure; hysteresis; Exact sciences and technology; Ferroelectricity and antiferroelectricity; Permittivity (dielectric function); Physics; Electrical conductivity; Electric field effects; Solid state reaction; Barium Bismuth Lanthanum Titanates Mixed; XRD; Relaxor; Microstructure; Permittivity; Activation energy; Ferroelectric hysteresis; Dielectric relaxation
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/42/7/075405

Barium lanthanum bismuth titanate (Ba1-(3/2)xLaxBi4Ti4O15, x = 0-0.4) ceramics were fabricated using the powders synthesized via the solid-state reaction route. X-ray powder diffraction analysis confirmed the above compositions to be monophasic and belonged to the m = 4 member of the Aurivillius family of oxides. The effect of the partial presence of La3+ on Ba2+ sites on the microstructure, dielectric and relaxor behaviour of BaBi4Ti4O15 (BBT) ceramics was investigated. For the compositions pertaining to x < = 0.1, the dielectric constant at both room temperature and in the vicinity of the temperature of the dielectric maximum (Tm) of the parent phase (BBT) increased significantly with an increase in x while Tm remained almost constant. Tm shifted towards lower temperatures accompanied by a decrease in the magnitude of the dielectric maximum (epsilonm) with an increase in the lanthanum content (0.1 < x < = 0.4). The dielectric relaxation was modelled using the Vogel-Fulcher relation and a decrease in the activation energy for frequency dispersion with increasing x was observed. The frequency dispersion of Tm was found to decrease with an increase in lanthanum doping, and for compositions corresponding to x > = 0.3, Tm was frequency independent. Well-developed P(polarization)-E(electric field) hysteresis loops were observed at 150 deg C for all the samples and the remanent polarization (2Pr) was improved from 6.3 muC cm-2 for pure BBT to 13.4 muC cm-2 for Ba0.7La0.2Bi4Ti4O15 ceramics. Dc conductivities and associated activation energies were evaluated using impedance spectroscopy.