Hole polarons in LaFeO 3 and La$_{1−x}$Sr$_x$FeO$_{3−δ}$ : Stability, trapping, mobility, effect of Sr concentration, and oxygen vacancies - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Physical Review B Année : 2023

Hole polarons in LaFeO 3 and La$_{1−x}$Sr$_x$FeO$_{3−δ}$ : Stability, trapping, mobility, effect of Sr concentration, and oxygen vacancies

Résumé

The stability, trapping and mobility of electron holes are investigated in lanthanum ferrite LaFeO$_3$ , and in La$_{1−x}$Sr$_x$FeO$_{3−δ}$ ($x$ ≈ 0.1, 0.4 and 0.6) by hybrid-density-functional and densityfunctional-theory $+ U$ calculations. In pure LaFeO$_3$ , the electron hole is more stable under a localized (polaronic) form than under a delocalized form, the energy difference (self-trapping energy) lie between ≈-0.3 and-0.4 eV. This self-trapped hole polaron is not strictly localized on a single Fe atom: instead, it occupies a quantum state made of a 3d orbital of a Fe atom, strongly hybridized with 2$p$ orbitals of four neighboring oxygens. The hole polaron is thus localized on five atoms (among which one single Fe), which can be described as the Fe$^{3+}$ oxidation into Fe$^{4+}$. Electron hole transport results from the combination of onsite reorientations and hoppings, with energy barriers estimated at ≈0.01–0.20 eV and 0.3–0.4 eV, respectively. The aliovalent substitution of lanthanum by strontium in LaFeO$_3$ induces the presence of localized electron holes, preserving the insulating character of La$_{1−x}$Sr$_x$FeO$_3$, regardless of the studied Sr concentration. The formation energy of the oxygen vacancy in La$_{1−x}$Sr$_x$FeO$_3$ (x ≈ 0.1 and 0.4) is estimated at ≈ +0.8 eV. This value is here successfully use to quantify the evolution of defect concentration as a function of the oxygen partial pressure
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Dates et versions

hal-03990325 , version 1 (15-02-2023)

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Cintia Hartmann, Jérôme Laurencin, Grégory Geneste. Hole polarons in LaFeO 3 and La$_{1−x}$Sr$_x$FeO$_{3−δ}$ : Stability, trapping, mobility, effect of Sr concentration, and oxygen vacancies. Physical Review B, 2023, 107 (2), pp.024104. ⟨10.1103/PhysRevB.107.024104⟩. ⟨hal-03990325⟩
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