This work demonstrates the critical role of orbital hybridizations in the FeO6 octahedral distortion, composition-driven phase transition, and bonding covalency in multiferroic (Bi1−xSmx)FeO3 (x = 0.10-0.20) ceramics in the vicinity of the morphotropic phase boundary (MPB). Sequential composition-driven transitions from the polar rhombohedral R3c to antipolar orthorhombic Pbam and then Pnma phases were revealed as the system crosses the MPB with increasing Sm. A coexistence of ferroelectric (FE) rhombohedral R3c and antiferroelectric (AFE) PbZrO3-like orthorhombic Pbam symmetries was identified by the 1/2{000}, 1/4{100}, 1/4{110}, 1/4{111}, and 1/4{121} superlattice diffractions at x = 0.12-0.16. In addition to R3c and Pbam space groups, the nonpolar SmFeO3-like orthorhombic Pnma space group becomes the predominant phase at x = 0.20 confirmed by the 1/2{100} superlattice diffractions. The Fe L3-edge and oxygen K-edge synchrotron X-ray absorptions indicate that the O 2p–Fe 3d and O 2p–Bi 6s/6p orbital hybridizations were decreased as the system approaches the MPB.

中文翻译：

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稀土掺杂的 BiFeO3 中的微纳米域结构和轨道杂化跨越同向相界

这项工作证明了轨道杂化在同形相界 (MPB) 附近的多铁性 (Bi1−xSmx)FeO3 (x = 0.10-0.20) 陶瓷中的 FeO6 八面体畸变、成分驱动的相变和键合共价中的关键作用）。当系统随着 Sm 的增加穿过 MPB 时，揭示了从极性菱面体 R3c 到反极性正交 Pbam 和 Pnma 相的顺序组成驱动转变。铁电 (FE) 菱形 R3c 和反铁电 (AFE) PbZrO3 类正交 Pbam 对称性的共存被确定为 1/2{000}、1/4{100}、1/4{110}、1/4{111 } 和 x = 0.12-0.16 处的 1/4{121} 超晶格衍射。除了 R3c 和 Pbam 空间群，非极性 SmFeO3 类正交 Pnma 空间群成为 x = 0 处的主要相。20 由 1/2{100} 超晶格衍射证实。Fe L3 边和氧 K 边同步加速器 X 射线吸收表明，随着系统接近 MPB，O 2p-Fe 3d 和 O 2p-Bi 6s/6p 轨道杂化减少。