Papers by Esther Rubavathi
Journal of Materials Science: Materials in Electronics
The talk presented at 29th Annual General Meeting Of Materials Research Society Of India And Nati... more The talk presented at 29th Annual General Meeting Of Materials Research Society Of India And National Symposium On Advances In Functional And Exotic Materials.
The talk presented at 29th Annual General Meeting Of Materials Research Society Of India And Nati... more The talk presented at 29th Annual General Meeting Of Materials Research Society Of India And National Symposium On Advances In Functional And Exotic Materials.
The tetragonal reentrant phase conversion (P4mm) is obtained from the phase coexistence of the te... more The tetragonal reentrant phase conversion (P4mm) is obtained from the phase coexistence of the tetragonal and the non-polar hexagonal phases (P63/mmc) as a structural effect due to Gd substitution in Ba1-yGdyTi1-xFexO3(x=0.05; y=0.005, 0.01 and 0.015) ceramics. The diffraction spots in the SAED patterns and the d-spacing of the HREM lattice fringes mainly evidence the coexistence of the structural phase. Rietveld refinement offers the bond length and the other structural data. Ti presents itself as Ti3+ and Ti4+ whereas Fe presents as Fe2+ and Fe3+, revealed by the XPS spectra. The octahedra partly change to pentahedral due to the creation of the charge compensating the oxygen vacancies and therefore the conversion from tetragonal to hexagonal phase occurs. The EPR feature corresponding to Ti3+ decreases progressively as the Gd content increases, which implies a decrease of the oxygen vacancy concentration. This facilitates reentrant tetragonal phase conversion. The observed ferroma...
Journal of Magnetism and Magnetic Materials, 2021
Abstract Artificial magnetoelectric material with enrichment of ME coupling coefficient was achie... more Abstract Artificial magnetoelectric material with enrichment of ME coupling coefficient was achieved via mixed-oxide route in cobalt substituted BaTiO3 multiferroics. The observed large ME coupling coefficient induced by spin-orbit interaction through the symmetry breaking due to the off-stoichiometry oxygen. Structural data extracted from the Rietveld refinement indicate the rapid arrival of a single hexagonal phase (P63/mmc) at the expense of the tetragonal phase (P4mm) above x=0.03. SAED patterns evidence to the structural coexistence, Morphotropic phase boundary (MPB), (P4mm+P63/mmc) in x = 0.01 and 0.03 while hexagonal phase alone in x≥0.05. Core-level XPS spectrum of Ba(3d), Ti (2p), Co (2p), O (1s) evidences the occurrence of the single oxidation state of Ba ion (Ba2+) and aliovalent of Ti (Ti4+ and Ti3+), Co (Co3+ and Co2+) and O (O2- and O1-) ions respectively. The weakening of ferroelectric loops arises from the formation of the non-ferroelectric hexagonal phase by the non-stoichiometric oxygen. For the first time, a high value of energy efficiency of 54.7% was achieved in the BaTi0.99Co0.01O3 sample. The ferromagnetism originated from the contributions of the super-exchange interaction. of Co3+(octahedral)-O2--Co3+(pentahedral) and double-exchange interaction (Co2+-O2--Co3+) Among all the samples, an excellent magnetoelectric coupling coefficient (αME) value of 29.6 mV/cm.Oe. is attained in the hexagonal BaTi0.93Co0.07O3 sample.
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Papers by Esther Rubavathi