Phase coexistence near the polymorphic phase boundary. (1st February 2019)

• Record Type: Journal Article
• Authors: Torres-Matheus, Oscar A.; García, R. Edwin; Bishop, Catherine M.
• Is Part Of: Acta materialia. Volume 164(2019)
• Page Start: 577
• Page End: 585
• Publication Date: 2019-02-01
• Subjects: Ferroelectric -- Interferroelectric transitions -- Phase field model -- Phase coexistence -- Phase stability; 00–01 -- 99-00; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2018.10.041
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: A novel multiphase field theory for ferroelectric systems in the vicinity of a polymorphic phase boundary (PPB) is developed by coupling the Landau-Devonshire thermodynamic potentials of the individual phases. The model naturally predicts metastable coexistence of the rhombohedral (R) and tetragonal (T) phases near the PPB temperature, T P P B = 43 C ∘, for the BZT-40BCT system, and provides a maximum temperature of coexistence, T C, 0 = 49.9 C ∘, in agreement with experiments. For T > T P P B, results show that metastable coexistence of two ferroelectric phases is a result of a phase transformation-induced polarization rotation plus switching mechanism. Metastable domains of the low-temperature R phase coexist with the high-temperature, thermodynamically stable T phase for long periods of time, from minutes to hours. For T < T P P B, the coexistence time is on the order of tens of seconds due to a decreased thermal energy that suppresses the polarization rotation plus switching mechanism. Further, the kinetics of macroscopic T → R phase transformation is accelerated by a large thermodynamic driving force and high mobility. Graphical abstract: Image 1