Mohanty, Hari Sankar and Dam, Tapabrata and Borkar, Hitesh and Pradhan, Dhiren K. and Mishra, K. K. and Kumar, Ashok and Sahoo, Balaram and Kulriya, Pawan K. and Cazorla, C. and Scott, J. F. and Pradhan, Dillip K.
(2019)
Structural transformations and physical properties of (1-x) Na0.5Bi0.5TiO3 - x BaTiO3 solid solutions near a morphotropic phase boundary.
Journal of Physics: Condensed Matter, 31 (7).
075401-0754014.
ISSN 0953-8984
Abstract
Piezoelectric and other physical properties are significantly enhanced at (or near) a morphotropic phase boundary (MPB) in ferroelectrics. MPB materials have attracted significant attention owing to both fundamental physics as well as the possibility of well-regulated energy and information storage devices which are dominated by lead (Pb)-based materials. Here, we report the crystal structure, Raman spectra, dielectric constant and polarization near the MPB of lead free (1 - x) Na0.5Bi0.5TiO3 - x BaTiO3 (0.00 <= x <= 0.10) solid-solution, prepared by sol-gel auto combustion technique and sintered by microwave sintering technique. With the addition of BaTiO3 into Na0.5Bi0.5TiO3, it induces a structural phase transition from R3c (a single phase) to R3c + P4mm (a dual phase) close to x = 0.06 and 0.07 and transform to a high symmetry tetragonal phase P4mm at higher compositions (x = 0.08 to 0.10) as evident from our x-ray Rietveld refinement and Raman spectroscopic results. We perform first-principles calculations based on density functional theory that confirm a structural transition from a rhombohedral to a tetragonal phase under increasing x. In the prepared solid solution, an anomalous enhancement of remnant polarization (2P(r)(0)) was observed for x = 0.06 and 0.07, which has been explained based on the existence of the MPB. On the other hand, the value of coercive field E-C(0) was found to be decreased linearly from x = 0.00 to 0.06; it is constant for higher compositions. Further details of the ferroelectric properties on the electric field poled samples have been studied and compared with the as-grown (unpoled) samples.
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