Hydrothermal synthesis of Ce/Zr co-substituted BiFeO3: R3c-to-P4mm phase transition and enhanced room temperature ferromagnetism

Zahra Adineh,Ahmad Gholizadeh

doi:10.1007/s10854-021-07067-y

Abstract

A facile hydrothermal method was used for fabricating phase-pure Bi1−xCexFe1−xZrxO3 (x = 0.00, 0.03, 0.06) multiferroic ferrites, and the dependence of structural, optical, and magnetic properties on the composition have been investigated. The samples were investigated by X-ray diffraction, Raman and Fourier transform infrared spectroscopies, scanning electron microscopy, UV–Vis spectroscopy, and vibrating sample magnetometer at room temperature. Structural results show that the structure of Bi1−xCexFe1−xZrxO3 ferrites is indexed to a rhombohedral structure with the R3c space group. However, the weakening in the intensity, the expansion of the line-width of all bands, and some band shifts observed in Raman spectra indicate a structural transition from rhombohedral (R3c) to pseudo-tetragonal (P4mm) phase as the content of Ce/Zr increases. Also, a significantly enhanced intensity of the A1–2 mode in Raman spectra means that there is a novel behavior of magnetic anisotropy in the Ce/Zr co-substituted samples. A significant increase in optical bandgap with increasing of the Ce/Zr co-substitution suggests that the materials are suitable for technological applications. Magnetic properties of the samples show a magnetic transition from antiferromagnetic to ferromagnetic phase due to the presence of the rhombohedral to the tetragonal phase transition, and exchange interaction between the 4f orbitals of the Ce3+/Ce4+ and the 3d orbitals of the Fe3+/Fe2+.

Highlights

BiFeO3(BFO) is the most famous multiferroic material having the antiferromagnetic Néel temperature (= 370 K) and the ferroelectric Curie temperature (= 830 K) which simultaneously shows a saturation polarization and magnetic moment of 90 μC/cm3 and 8-9 emu/cm3, respectively [1]
Since the structure of sample x = 0.06 is a mixture of the tetragonal (P4mm) and rhombohedral (R3c) phases, the peak overlap of the (012)R with the (001)T and the peak overlap of the (024)R with the (002)T occurs. These findings could be related to the fact that the lower-symmetry rhombohedral structure of BFO gradually transforms into a higher-symmetry tetragonal structure due to the changes of bond lengths Bi-O and Fe-O after the Ce3+/Zr4+ doping into BFO, which is discussed further below
We have summarized the key points from our work on the Ce/Zr co-substituted BFO as follows: (1) the X-ray diffraction (XRD) and Raman spectroscopy results indicate a rhombohedral-tetragonal phase structural transition

Summary

Introduction

BiFeO3(BFO) is the most famous multiferroic material having the antiferromagnetic Néel temperature (= 370 K) and the ferroelectric Curie temperature (= 830 K) which simultaneously shows a saturation polarization and magnetic moment of 90 μC/cm and 8-9 emu/cm, respectively [1]. Recent studies revealed that a strategy of co-doping of the Bi-site, and Fe-site can significantly improve the magnetic and ferroelectric properties of BFO nanoparticles, [11,12,13,14,15,16,17,18,19,20,21]. We recently reported that the A-site (Nd, Y, Gd) and B-site (Mn, Zr) co-substitution of BFO have a result to reduce the particle size to less than 62 nm which will destruct or suppress the magnetic spiral structure [6,7]. Optical, and magnetic properties indicate novel behaviors of the pure single-phase Bi1-xCexFe1-xZrxO3 (x = 0.00, 0.03, 0.06) hydrothermally synthesized with improved magnetic properties. The hysteresis loops of the samples were recorded using the VSM 7407 Lake Shore's vibrating sample magnetometer at room temperature and a maximum magnetic field of 2T

Results and discussion

Raman and FTIR spectroscopies

Optical characterization

Magnetic measurements

Summary