Phenomenological theory of phase transitions in the MPB region of (1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals. (3rd May 2020)

• Record Type: Journal Article
• Authors: Jang, Kum-Ok; Kim, Il-Hwan; Kim, Il-Hun; Im, Sok-Gil; Sin, Kye-Ryong; Kim, Chol-Jin
• Is Part Of: Phase transitions. Volume 93:Number 5(2020)
• Page Start: 439
• Page End: 454
• Publication Date: 2020-05-03
• Subjects: PMN-PT crystal -- higher-order Landau–Ginzburg–Devonshire theory -- structural stability -- phase diagram -- dielectric response; Phase transformations (Statistical physics) -- Periodicals; 530.47405
• DOI: 10.1080/01411594.2020.1746965
• Languages: English
• ISSNs: 0141-1594

Abstract

ABSTRACT: A higher-order Landau–Ginzburg–Devonshire theory is proposed to describe phenomenologically the complex phase transitions in the MPB region of the relaxor ferroelectric (1− x )Pb(Mg1/3 Nb2/3 )O3 - x PbTiO3 (PMN-PT) single crystals. Using the singularity theory, a structurally stable 10th-order potential with four varying expansion coefficients ( a 1, a 11, a 2 and a 12 ) depending on temperature and composition is found out. By studying on two- and three-dimensional sections of a four-dimensional phase diagram a 1 - a 11 - a 2 - a 12 in the space of phenomenological parameters, the range of coefficient parameters by which the structural stability of the potential model can be guaranteed is determined. The theoretical temperature-composition phase diagram is constructed and it is shown that this is in good agreement with both recent experimental data and first-principle calculation for the symmetry change. Moreover, temperature dependence of dielectric constants for various compositions is studied.