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dc.contributor.advisorVarma, K B R
dc.contributor.authorKumar, Sunil
dc.date.accessioned2018-07-30T14:12:35Z
dc.date.accessioned2018-08-28T11:26:22Z
dc.date.available2018-07-30T14:12:35Z
dc.date.available2018-08-28T11:26:22Z
dc.date.issued2018-07-30
dc.date.submitted2011
dc.identifier.urihttp://etd.iisc.ac.in/handle/2005/3989
dc.identifier.abstracthttp://etd.iisc.ac.in/static/etd/abstracts/4785/G25241-Abs.pdfen_US
dc.description.abstractBismuth 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.en_US
dc.language.isoen_USen_US
dc.relation.ispartofseriesG25241en_US
dc.subjectFerroelectricsen_US
dc.subjectPerovoskite Materialsen_US
dc.subjectBismuth Layer-structured Ferroelectrics (BSLFs)en_US
dc.subjectAurivillius Oxidesen_US
dc.subjectPiezoeletricsen_US
dc.subjectFerroelectric Ceramicsen_US
dc.subjectAurivillius Oxidesen_US
dc.subjectBaBi4Ti4O15 Ceramicsen_US
dc.subjectBaBi4Ti4O15 Ceramicsen_US
dc.subjectNa0.5La0.5Bi4Ti4O15 Ceramicsen_US
dc.subjectNaBi2Nb3O12 (A = Sr, Ca) Ceramicsen_US
dc.subjectAurivillius Oxide Ceramicsen_US
dc.subjectRelaxor Ferroelectricsen_US
dc.subjectBi4Ti2Nb0.5Fe0.5O12 Ceramicsen_US
dc.subjectBarium Bismuth Titanate Ceramicsen_US
dc.subjectBaLaxBi4-xTi4O15 Ceramicsen_US
dc.subjectNa0.5La0.5Bi4Ti4O15 Ceramicsen_US
dc.subjectSrNaBi2Nb3O12 Ceramicsen_US
dc.subjectRelaxor Ferroelectricsen_US
dc.subject.classificationMaterials Scienceen_US
dc.titleInvestigations into the Synthesis, Structural, Dielectric, Piezoelectric and Ferroelectric Properties of Lead-Free Aurivillius Family of Oxidesen_US
dc.typeThesisen_US
dc.degree.namePhDen_US
dc.degree.levelDoctoralen_US
dc.degree.disciplineFaculty of Scienceen_US


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