Raman Vibrations, Domain Structures, and Photovoltaic Effects in A‐Site La‐Modified BiFeO₃Multiferroic Ceramics

Abstract

Micro-Raman spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy (TEM), oxygen vacancies, synchrotron X-ray absorption spectroscopy, magnetizations, optical band gaps, and photovoltaic (PV) effects have been studied in (Bi 1 -x La x )FeO 3 (BFO100xL) ceramics for x = 0.0, 0.05, 0.10, and 0.15. XRD, Raman spectra, and TEM confirm a rhombohedral R3c symmetry with the tilted FeO 6 oxygen octahedra in all compounds. The low-frequency Raman vibrations become broader and shift toward higher frequency as La 3+ increases. Fe K-edge synchrotron X-ray absorptions reveal that Fe

Magnetization, phonon, and X-ray edge absorption in barium-doped BiFeO3 ceramics

“…Linear antiferromagnetic behavior and electric leakage have limited BiFeO 3 for electromagnetic applications. A-site substitutions of rare-earth elements onto the BiFeO 3 perovskite cell have been employed to enhance ferromagnetic, ferroelectric, and photovoltaic responses [8][9][10][11]. A-site substitutions of alkaline earth metal elements in BiFeO 3 , i.e., (Bi 1-x A x ) FeO 3 (A = Ca, Sr, Ba), have also demonstrated an improvement of magnetic and ferroelectric properties [12][13][14][15][16][17][18][19][20][21][22][23].…”

Micro‐to‐nano domain structure and orbital hybridization in rare‐earth‐doped BiFeO3 across morphotropic phase boundary

“…Similarly decreased average grain sizes were also observed in (Bi 1Àx La x )FeO 3 ceramics with increasing La. 14 The minimal grain size occurs in BFO14Sm may result from the structural instability as the system approaches the MPB. It was suggested that the grain size is associated with oxygen vacancies which can enhance ion migration to cause grain growth during the sintering process.…”

“…BFO10Sm, BFO12Sm, BFO14Sm, BFO16Sm, and BFO20Sm represent compounds of x = 0.10, 0.12, 0.14, 0.16, and 0.20, respectively. Similarly decreased average grain sizes were also observed in (Bi 1− x La x )FeO 3 ceramics with increasing La . The minimal grain size occurs in BFO14Sm may result from the structural instability as the system approaches the MPB.…”

“…It was reported that the (Bi 1− x RE x )FeO 3 system favors the orthorhombic Pnma ( a − a − c + tilt system) rather than rhombohedral R 3 c ( a − a − a − tilt system) as RE increases . The R 3c structure was observed in the low RE compounds of (Bi 1− x RE x )FeO 3 ( RE = La, Nd, Sm, Gd, Dy) for x ≤ 0.1 . A transition from a ferroelectric R 3 c to a nonpolar Pnma structure was reported upon heating in (Bi 1− x RE x )FeO 3 for average A‐site ionic radii near 1.352 Å …”

“…12 The R3c structure was observed in the low RE compounds of (Bi 1Àx RE x )FeO 3 (RE = La, Nd, Sm, Gd, Dy) for x ≤ 0.1. 4,[13][14][15] A transition from a ferroelectric R3c to a nonpolar Pnma structure was reported upon heating in (Bi 1Àx RE x )FeO 3 for average A-site ionic radii near 1.352 Å. 16 In (Bi 1Àx Sm x )FeO 3 system, a temperature-composition MPB between a coexistence (R3c and PbZrO 3 -like orthorhombic structures) and an orthorhombic Pnma symmetry was proposed for 0.09 ≤ x ≤ 0.14.…”