This study presents synthesis by the Pechini method and characterization of Bi1−xGdxFeO3 powders (0.00 ≤ x ≤ 0.20), providing new insights into the effects of gadolinium substitution on the structural, magnetic, and thermal properties of BiFeO3. Unlike previous studies, this work identifies a previously unreported double structural transition, from rhombohedral to cubic symmetry at x = 0.10, and from cubic to orthorhombic symmetry for x ≥ 0.15, demonstrating the critical role of Gd concentration. The magnetization measurements at room temperature exhibited enhanced ferromagnetic-like behavior, with potential implications for improving the material’s photocatalytic and multiferroic performance. Additionally, differential scanning calorimetry emphasized the material’s thermal stability. These findings contribute to a deeper understanding of how Gd substitution modifies the properties of BiFeO3, offering potential for optimizing applications in energy storage, spintronics, and catalysis.

Rare-earth substituted multiferroic Bi1-xRExFeO3 powders with chemical compositions (x = 0.05, 0.15, 0.20 and RE = Nd3+; Eu3+) are synthesized by sol-gel method. The powder X-ray diffraction results manifest that samples are in single phase (R3c) for x < 0.15; the structural phase transformation from the distorted perovskite R3c to the ideal perovskite (Pm3 m) was made for BFO-Nd at x = 0.15 and for BFO-Eu (BEFO) at x = 0.20. Theoretical analyses allowed us to propose & UGamma;4 (k = 0, 0, 0) as the irreducible representation associated to the distortion of the ideal perovskite Pm3 m to the R3c distorted one, where the displacement of Fe atom along [0 0 1] axis is considered as so the parameter order & eta; = (0; 0; & eta;3), which drives the transition Pm3 m -R3c. Dielectric properties of Bi1-xRExFeO3 change noticeably with concentration and nature of RE-doping. The increase of Nd and Eu concentration decreases clearly the dielectric temperature anomalies corresponding to the ferroelectricparaelectric phase transitions, which are more shifting towards lower temperature when the dopant is Eu. Magnetic measurements indicate that antiferromagnetic BFO-Nd (BNFO) powders became ferromagnetic at (0.15 & LE;x & LE; 0.2), while the BFO-Eu (BEFO, x & LE; 0.15) compounds, antiferromagnetic with a small remanant magnetization, become weak ferromagnetic when x = 0.20.

Bi 1-x Eu x FeO 3 micropowders 0 ≤ x ≤ 0.20 were synthesized by sol-gel method. X-ray diffraction shows that the crystal structure changes from rhombohedral to cubic symmetry at x = 0.20 . Dielectric properties and loss factor were investigated as a function of temperature. Neel temperature T N of the compounds was measured by differential scanning calorimetry and found to decrease from 668 K to 646 K for 0 ≤ x ≤ 0.15 and bounce to 667 K for x = 0.20 . The Curie temperature T C which corresponds to the transition from ferroelectric to paraelectric phases was checked out using differential thermal analysis measurements. The T C value increases from 1130 K to 1135 K for 0 ≤ x ≤ 0.15 while no transition was detected for x = 0.20 in accordance with the structural transition from R3c to centrosymmetric Pm3m phase.

We have found substantial increase of the infrared third harmonic generation (THG) for the fundamental wavelength 9.4 mu m of microsecond CO2 laser for Bi2Fe4O9 microcrystalline powders. Additional enhancement of the THG signal was achieved by use of Er:glass 20 ns laser generating at 1540 nm before the IR probing of the THG. At the same time the analogous effect for the photoinduced two-photon absorption (TPA) was substantially less. The observed effect is explained within a framework of phenomenological description. Principal role here is played by magneto-electric interactions due to interactions of ferroelectric polarizations and ferromagnetic states. The observed effect may be used for creation of IR laser magneto-optical materials. (C) 2016 Elsevier B.V. All rights reserved.