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Your search keyword '"Lalitha, K. V."' showing total 3 results
Start Over Author "Lalitha, K. V." Journal applied physics letters
3 results on '"Lalitha, K. V."'

1. Propensity for spontaneous relaxor-ferroelectric transition in quenched (Na1/2Bi1/2)TiO3-BaTiO3 compositions

Author

Jurij Koruza, Jürgen Rödel, and Lalitha K. V.

Subjects
010302 applied physics, Permittivity, Quenching, Phase boundary, Materials science, Physics and Astronomy (miscellaneous), Condensed matter physics, Annealing (metallurgy), High Energy Physics::Lattice, Depolarization, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Ferroelectricity, Condensed Matter::Materials Science, 0103 physical sciences, Thermal, 0210 nano-technology, Relaxor ferroelectric
Abstract

Recently, quenching lead-free non-ergodic relaxor Na1/2Bi1/2TiO3-BaTiO3 (NBT-BT) materials has been reported to increase the thermal depolarization temperature and enhance the lattice distortion. Driven by the conjecture that enhanced lattice distortion is typically associated with the onset of ferroelectric order, two non-ergodic relaxor NBT-BT compositions at the morphotropic phase boundary were investigated. As evident from the temperature-dependent permittivity, both compositions exhibit a stabilization of ferroelectric order upon quenching. An increase in the depolarization temperature by 40–60 °C is observed. Moreover, the composition with higher tetragonality undergoes a spontaneous relaxor-ferroelectric transition upon quenching. Annealing in oxygen atmosphere is shown to revert back the quenching-induced ferroelectric order to the relaxor state.Recently, quenching lead-free non-ergodic relaxor Na1/2Bi1/2TiO3-BaTiO3 (NBT-BT) materials has been reported to increase the thermal depolarization temperature and enhance the lattice distortion. Driven by the conjecture that enhanced lattice distortion is typically associated with the onset of ferroelectric order, two non-ergodic relaxor NBT-BT compositions at the morphotropic phase boundary were investigated. As evident from the temperature-dependent permittivity, both compositions exhibit a stabilization of ferroelectric order upon quenching. An increase in the depolarization temperature by 40–60 °C is observed. Moreover, the composition with higher tetragonality undergoes a spontaneous relaxor-ferroelectric transition upon quenching. Annealing in oxygen atmosphere is shown to revert back the quenching-induced ferroelectric order to the relaxor state.

Published
2018

2. Hardening of electromechanical properties in piezoceramics using a composite approach.

Author

Lalitha, K. V., Riemer, Lukas M., Koruza, Jurij, and Rödel, Jürgen

Subjects
*PIEZOELECTRIC ceramics, *HARDENING (Heat treatment), *ELECTROMECHANICAL effects, *COMPOSITE materials, *DOPING agents (Chemistry), *ULTRASONIC motors
Abstract

Piezoelectric applications such as ultrasonic motors, transformers and therapeutic ultrasonics demand high power generation with low losses, which is facilitated by "hard" ferroelectrics. Hardening of piezoelectric properties, characterized by high mechanical quality factor (Qm), is usually achieved by doping with lower valence elements, thereby tailoring the domain wall dynamics. In the present study, we demonstrate a hardening mechanism by developing composites of 0.94(Na1/2Bi1/2)TiO3-0.06BaTiO3 (NBT-6BT) with ZnO inclusions, as an alternative to chemical modifications. A decrease in the saturation polarization and total strain, higher internal bias fields, lower hysteretic losses and a two-fold increase in Qm are observed in comparison to NBT-6BT. The composite with 0.1 mole ratio of ZnO exhibits the highest Qm of 320 with d33=125 pC/N and Kp=0.29. A one-to-one correspondence between the increase in Qm and the decrease in the domain wall mobility is established from the ac field dependence of permittivity, in the framework of the Rayleigh law. A further increase in ZnO content beyond a mole ratio of 0.1 reduces Qm, but retains it at a higher level, as compared to NBT-6BT. The results are explained based on the poling-induced strain incompatibility between the matrix and the hard ZnO phase. This composite approach is therefore considered a generic hardening concept and can be extended to other ferroelectric systems. [ABSTRACT FROM AUTHOR]

Published
2017
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3. Field induced domain switching as the origin of anomalous lattice strain along non-polar direction in rhombohedral BiScO3-PbTiO3 close to the morphotropic phase boundary.

Author

Lalitha, K. V., Fancher, Chris M., Jones, Jacob L., and Ranjan, Rajeev

Subjects
*X-ray diffraction, *CRYSTAL lattices, *STRAINS & stresses (Mechanics), *BISMUTH compounds, *LEAD titanate, *CRYSTAL morphology
Abstract

The lattice strain and domain switching behavior of xBiScO3-(1-x)PbTiO3 (x=0.40) was investigated as a function of cyclic field and grain orientation by in situ X-ray diffraction during application of electric fields. The electric field induced 200 lattice strain was measured to be five times larger than the 111 lattice strain in pseudorhombohedral xBiScO3-(1-x)PbTiO3 (x=0.40). It is shown that the anomalous 200 lattice strain is not an intrinsic phenomenon, but arises primarily due to stress associated with the reorientation of the 111 domains in dense polycrystalline ceramic. [ABSTRACT FROM AUTHOR]

Published
2015
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