Phase Transitions, Magnetic and Piezoelectric Properties of Rare‐Earth‐Substituted BiFeO₃ Ceramics

Abstract

The concentration range of the stability of polar (R3c) and antipolar phases in the Bi 1Àx RE x FeO 3 (RE-La -Dy) solid solutions has been determined by X-ray study of the polycrystalline samples. Both polar and antipolar phases become less stable with a decrease of the rare earth ionic radii. It is stimulated by a reduction of the rare-earth ions polarizability with a decrease in ionic radii. The antipolar phase is characterized by a weak ferromagnetic state, whereas the polar one exhibits dominantly antiferromagnetic behavior near the polar-antipolar morphotropic boundary. The local piezoelectric response decreases with increase in antipolar phase content in the mixed polarantipolar structural state. It is suggested that the piezoelectric activity is associated with polar (R3c) phase.

Phase coexistence in Bi1−x Pr x FeO3 ceramics

“…The crystal structure of Bi 0.89 Pr 0.11 FeO 3 compound at room temperature has been successfully refined assuming 90% of the rhombohedral phase (R-phase, space group R3c) and 10% of the orthorhombic phase (O 2 -phase). The rhombohedral phase is the same as observed in Bi 1-x Pr x FeO 3 compounds with lower dopant concentration x < 0.11 [10,14]. The orthorhombic phase has been refined using Pnam space group with a lattice metric √2a p *2√2a p *4a p (a p is the fundamental perovskite lattice parameter).…”

“…the incommensurately modulated crystal structure has been observed in the La-doped compounds [8,9]. In addition, both La-and Prdoped systems manifest isothermal structural transition [5,10]. Temperature evolution of the crystal structure obtained for the Pr-doped compounds differs significantly from that of the compounds doped with other rare-earth ions.…”

“…Temperature evolution of the crystal structure obtained for the Pr-doped compounds differs significantly from that of the compounds doped with other rare-earth ions. The most intriguing feature of the Bi 1-x Pr x FeO 3 crystal structure has been observed near the transition to the non-polar orthorhombic phase where the coexistence of the rhombohedral and both orthorhombic phases has been suggested [10][11][12].…”

“…Ceramic samples of Bi 1-x Pr x FeO 3 (molar concentrations 0.11, 0.125, and 0.15) were prepared by the two-stage solid-state reaction technique [10]. High-purity oxides taken in a stoichiometric ratio were thoroughly mixed using a planetary ball mill (Retsch PM 200).…”

Magnetic structure of an incommensurate phase of La-dopedBiFe0.5Sc0.5O3: Role of antisymmetric exchange interactions

“…Perovskite materials derived from the well-known multiferroic BiFeO 3 by various substitutions exhibit a variety of structural phases with interesting properties and improved functionality [1][2][3][4][5][6][7][8][9][10][11][12]. The electronic degree of freedom related to the lone pair nature of Bi 3+ usually results in polar/antipolar atomic displacements in these materials.…”