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Investigations into the Synthesis, Structural, Dielectric, Piezoelectric and Ferroelectric Properties of Lead-Free Aurivillius Family of Oxides

Electronic Theses of Indian Institute of Science

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Title Investigations into the Synthesis, Structural, Dielectric, Piezoelectric and Ferroelectric Properties of Lead-Free Aurivillius Family of Oxides
 
Creator Kumar, Sunil
 
Subject Ferroelectrics
Perovoskite Materials
Bismuth Layer-structured Ferroelectrics (BSLFs)
Aurivillius Oxides
Piezoeletrics
Ferroelectric Ceramics
Aurivillius Oxides
BaBi4Ti4O15 Ceramics
BaBi4Ti4O15 Ceramics
Na0.5La0.5Bi4Ti4O15 Ceramics
NaBi2Nb3O12 (A = Sr, Ca) Ceramics
Aurivillius Oxide Ceramics
Relaxor Ferroelectrics
Bi4Ti2Nb0.5Fe0.5O12 Ceramics
Barium Bismuth Titanate Ceramics
BaLaxBi4-xTi4O15 Ceramics
Na0.5La0.5Bi4Ti4O15 Ceramics
SrNaBi2Nb3O12 Ceramics
Relaxor Ferroelectrics
Materials Science
 
Description Bismuth layer-structured ferroelectrics have received significant attention recently due to their fairly high TC and good fatigue endurance which make them important candidates for non-volatile ferroelectric random access memories (Fe-RAMs) as well as for the piezoelectric device applications at high temperatures. Structure of these compounds is generally described as the pseudo-perovskite block (An-1BnO3n+1)2- sandwiched between the bismuth oxide layers (Bi2O2)2+ along the c-axis, where n represents the number of corner sharing BO6 octahedra forming the perovskite-like slabs. Only a few compounds belonging to this family show relaxor behavior (frequency dependent diffuse phase transition). Relaxor ferroelectrics are very attractive for a variety of applications, such as capacitors, sensors, actuators, and integrated electromechanical systems.
The present work attempts to understand the mechanism of relaxor behavior in Aurivillius oxides as well as to improve the piezoelectric and ferroelectric properties of some of the known phases. Details pertaining to the fabrication and characterization of BaBi4Ti4O15 (n = 4 member of Aurivillius family of oxides) ceramics are presented. X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were employed to probe the structural and microstructural details. The contribution of irreversible domain wall movement to the room temperature dielectric constant and polarization was quantitatively evaluated using the nonlinear dielectric response. Dielectric dispersion and conduction mechanism of these ceramics are also explicated using the complex impedance spectroscopy.
The effects of La3+ and Ca2+ doping on the phase transition behavior and other properties of BaBi4Ti4O15 are investigated. La3+ doping for Bi3+ was found to strengthen the relaxor behavior. New compounds such as CaNaBi2Nb3O12, SrNaBi2Nb3O12, Na0.5La0.5Bi4Ti4O12, etc. belonging to the Aurivillius family of oxides have been synthesized and investigations concerning their structural, dielectric and ferroelectric properties are presented. Rietveld refinement of room temperature X-ray powder data suggested that CaNaBi2Nb3O12 and SrNaBi2Nb3O12crystallize in the orthorhombic space group B2cb. SrNaBi2Nb3O12 ceramics exhibited frequency-dependent Tm which follows the Vogel-Fulcher relation implying a relaxor nature. No frequency dependence of Tm was observed for CaNaBi2Nb3O12 ceramics. Polarization - electric field hysteresis loops recorded well above Tm confirmed the coexistence of polar and non-polar domains in SrNaBi2Nb3O12 ceramics. Dielectric anomaly observed around 675 K for CNBN corresponds to the ferroelectric to paraelectric phase transition which is accompanied by the change in crystal structure from orthorhombic to tetragonal. Fe and Nb co-doped Bi4Ti3O12 ceramics were fabricated and characterized for their structural, electrical and magnetic properties.
 
Contributor Varma, K B R
 
Date 2018-07-30T14:12:35Z
2018-07-30T14:12:35Z
2018-07-30
2011
 
Type Thesis
 
Identifier http://etd.iisc.ernet.in/2005/3908
http://etd.iisc.ernet.in/abstracts/4785/G25241-Abs.pdf
 
Language en_US
 
Relation G25241