Complex antipolar2×4×22structure withPnmasymmetry in

Abstract

First principles calculations are done for a √ 2 × 4 × 2 √ 2 P nma structure, which has been recently discussed in several attempts to describe experiments in complex magnetoelectric perovskites and which experimentally was shown to compete with several ferroelectric phases. This makes these materials extremely attracting as switchers, starters, field-stimulated capacitors, high-voltage converters, transmitters, etc. The relative energies of the √ 2 × 4 × 2 √ 2 P nma structure have been calculated from first principles and analyzed as a function of pressure in BiFeO 3 . The stability of two polymorphs of the √ 2 × 4 × 2 √ 2 P nma structure has been studied for solid solution BiFe 1/2 Sc 1/2 O 3 . The main distortions and relative energies of these two polymorphs in BiFe 1/2 Sc 1/2 O 3 , in terms of P m3m parent symmetry, have been calculated from first principles as well.

Phase formation in the (1- y )BiFeO 3 - y BiScO 3 system under ambient and high pressure

“…Structure of the as-prepared samples was found to be orthorhombic Pnma similar to that reported for the BiFe 1-x Mn x O 3 solid solutions in the range of 0.15≤x≤0.40 synthesized under high pressure [10]. Combination of the antipolar displacements of bismuth and the ++--oxygen octahedral tilting results in a 2a p 4a p 22a p superstructure (a p ~ 4 Å is the pseudocubic unit-cell parameter) of the Pnma phase in BiFe 0.50 Sc 0.50 O 3 [24,25].…”

“…Three types of the XRD patterns different in terms of splitting of the fundamental reflections were observed: rhombohedral (similar to that of BiFeO 3 ) at y≤0 25,. orthorhombic (similar to the antipolar polymorph of BiFe 0.50 Sc 0.50 O 3 [24]) at 0.30≤y≤0.60, and monoclinic (similar to that of BiScO 3 [37]) at y=0.70.…”

Antisymmetric exchange in La-substituted BiFe0.5Sc0.5O3 system: symmetry adapted distortion modes approach

“…We demonstrate the approach on a 35 % La-substituted Bi 1−x La x Fe 0.5 Sc 0.5 O 3 . This is a particular composition studied as a part of our systematic research of multiferroic properties of the Bi 1−x La x Fe 1−y Sc y O 3 perovskites obtained under extreme conditions [13,14]. Bi 0.65 La 0.35 Fe 0.5 Sc 0.5 O 3 crystalizes into a distorted perovskite structure with orthorhombic Pnma symmetry and exhibits a long-range magnetic ordering below T N ~ 220 K. The crystal and magnetic structures of the Bi 0.65 La 0.35 Fe 0.5 Sc 0.5 O 3 perovskite were fully characterized based on neutron diffraction data.…”

Temperature-Induced Reversible and Irreversible Transitions between Metastable Perovskite Phases in the BiFe1−yScyO3 Solid Solutions

“…To date, the most studied composition of the BiFe 1−y Sc y O 3 series is that, corresponding to y = 0.50 [11]. It was revealed that two nonequivalent structures with the same Pnma space group are possible for BiFe 0.50 Sc 0.50 O 3 [11,20]. In addition, an annealing-stimulated polymorphic transformation has been found.…”