Critical analysis of the isosymmetric transition and phase diagram of BiFeO3-PbTi O3

Singh, DN and Singh, RP and Bhattacharyya, S and Ranjan, R (2024) Critical analysis of the isosymmetric transition and phase diagram of BiFeO3-PbTi O3. In: Physical Review B, 110 (13).

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Abstract

Morphotropic phase boundary (MPB) ferroelectric systems are interesting and attractive for their ability to exhibit enhanced electromechanical response. In general, MPB represents a symmetry-breaking interferroelectric instability in the composition-temperature phase diagram of ferroelectric alloys. Deviating from this conventional trend, the ferroelectric alloy system (1-x) BiFeO3-(x)PbTiO3 appears to exhibit a rare phenomenon of symmetry preserving tetragonal (T1) to tetragonal (T2) isostructural/isosymmetric transition on heating. Here, we resolve this puzzle by studying structural evolution under thermal cycling, the temporal evolution of the structure under isothermal conditions, and Landau-Devonshire phenomenological calculations. We prove that (i) what appears as an isosymmetric T2 at high temperature is not an equilibrium phase, (ii) the equilibrium phase at high temperature is rather of rhombohedral symmetry, and (iii) the rhombohedral phase is precluded during the heating cycle (but stabilized during the cooling cycle) due to internal strain constraints. The understanding developed here has broader implications with regard to the role of internal strain in influencing the stability of phases and, thereby, the structure-sensitive properties of functional materials. © 2024 American Physical Society.

Item Type:	Journal Article
Publication:	Physical Review B
Publisher:	American Physical Society
Additional Information:	The copyright for this article belongs to the publishers.
Keywords:	Binary alloys; Bismuth alloys; Calcium alloys; Crystal symmetry; Ferroelectric devices; Ferroelectric materials; Ferroelectricity; Iron alloys; Lead alloys; Single crystals; Structural properties; Ternary alloys, Critical analysis; Electromechanical response; Equilibrium phasis; Ferroelectric system; Highest temperature; Internal strains; Morphotropic phase boundaries; PbTi O3; Symmetry breakings; Temperature phase, Thermal cycling
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	04 Dec 2024 17:21
Last Modified:	04 Dec 2024 17:21
URI:	http://eprints.iisc.ac.in/id/eprint/86898

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