Multiferroism and enhancement of material properties across the morphotropic phase boundary of BiFeO3-PbTiO3

Abstract

Strong phase-change magnetoelectric responses have been anticipated by a first-principles investigation of phases in the perovskite BiFeO 3 -BiCoO 3 solid solution, specifically at the morphotropic phase boundary (MPB) between the multiferroic rhombohedral and tetragonal polymorphs. This might be a general property of multiferroic MPBs and a novel promising approach for room temperature magnetoelectricity, which requires the identification of suitable material systems. We present here a comprehensive description of the electrical and electromechanical properties across one such system; the perovskite BiFeO 3 -PbTiO 3 solid solution. All the temperature dependence of dielectric permittivity, ferroelectric hysteresis loops, and piezoelectric coefficients have been obtained, and are discussed in relation to the previously reported perovskite structural evolution. Results show ceramic materials to be very promising for ferroelectric random access memories (remnant polarization as high as 63 lC cm À2 with a comparatively low coercive field of 4.5 kV mm À1 for MPB compositions) and high temperature electromechanical transduction (crystal piezoelectric coefficient of 87 pC N À1 with a Curie temperature above 873 K). Moreover, the occurrence of phase changes between the monoclinic and tetragonal polymorphs under high electric fields is indicated, while the canted antiferromagnetic character of the phases involved is corroborated. V C 2014 AIP Publishing LLC.

Perovskite solid solutions with multiferroic morphotropic phase boundaries and property enhancement

“…70 A significant irreversibility, that is divergence of the ZFC and FC curves has been recently described for a material with x ¼ 0:675 at the spin reorientation transition, which strongly suggests the appearance of spin canting and weak ferromagnetism at the magnetic instability. 71 This effect is illustrated in Fig. 10, where the spin reorientation transition at 380 K is marked with an arrow.…”

“…Therefore, this very high number can only be understood if a significant phase-change contribution to switching is assumed. 71,72 Indeed, a distinctive phase-change electromechanical response was revealed when temperature was raised above 425 K, and the threshold field was decreased below the applied ones. 72 The evolution of the electrical and electromechanical linear coefficients across the perovskite solid solution series was outstanding too.…”

“…This has been proposed to result in the release of the ferroelectric domain walls, initially clamped by the presence of aligned Fe 2þ -oxygen vacancy dipolar defects. 71,72 Indeed, this treatment was not efficient enough to obtain fully saturated loops for x ¼1, that is BiFeO 3 , because the transition temperature of 1100 K could not be exceeded in this case. Perovskite decomposition was already triggered at a temperature as low as 1063 K for the multiferroic edge member.…”

“…72 The evolution of the electrical and electromechanical linear coefficients across the perovskite solid solution series was outstanding too. 71 Permittivity and the charge piezoelectric coefficient are also given in Fig. 13.…”

Nanoscale Ferroelectrics and Multiferroics

“…This approach requires the identification and study of suitable material systems, like the BiFeO 3 -PbTiO 3 solid solution, recently shown to present such a multiferroic MPB, for which the enhancement of properties was described [54,55].…”