Effect of Dy-substitution on the structural, vibrational, and multiferroic properties of BiFeO3 nanoparticles

Abstract

Dysprosium (Dy) modified BiFeO3 [Bi1−xDyxFeO3 (x = 0.05, 0.10, and 0.15)] nanoparticles have been synthesized by a low temperature co-precipitation method. Rietveld analysis of X-ray diffraction data reveals a transformation from rhombohedral structure to orthorhombic structure with increase in the Dy concentration. From the transmission electron microscopy analysis, it is observed that the particle sizes of Bi1−xDyxFeO3 (x = 0.05, 0.10, and 0.15) nanoparticles range between 50–70, 40–50, and 30–50 nm, respectively. Raman spectra of Bi1−xDyxFeO3 (x = 0.05) belonging to rhombohedral (R3c) structure show 4A1 and 7E fundamental Raman modes in the range of 100–650 cm−1 and two-phonon scattering modes such as 2A4 (longitudinal optical), 2E8 (transverse optical (TO)), and 2E9 (TO) in the range of 950–1270 cm−1. Suppression, broadening, and shifting of Raman modes have been observed with further increase in Dy concentration. The fundamental Raman modes of Bi1−xDyxFeO3 (x = 0.15) are assigned under orthorhombic (pnma) rather than rhombohedral (R3c) as the Rietveld analysis of X-ray diffraction data predicts a structural transformation for this particular composition. A complete suppression of two phonon modes has been noticed for this composition. An anomaly in the temperature dependent dielectric studies has been observed in all the samples at the vicinity of Neel temperature indicating a magnetic ordering, and an increase in magnetization with increase of Dy concentration in BiFeO3 is noticed from the room temperature magnetic studies. P–E hysteresis loop studies show a decrease of remnant polarization (Pr) with the increase in Dy concentration and disappearance of hysteresis loop occurs for Bi1−xDyxFeO3 (x = 0.15) depicting a transformation from non-centrosymmetric (R3c) to centrosymmetric (Pnma) system.

Dy doped BiFeO 3 : A bulk ceramic with improved multiferroic properties compared to nano counterparts

“…For the 10% Dy doped BiFeO 3 nanoparticles, the reported M r value was ∼ 0.02 emu/g in Ref. [27], whereas, our obtained M r for BDFO bulk material is 0.118 emu/g. Again, for the same composition synthesized by chemical co-precipitation [27], the obtained maximum magnetization was 0.47 emu/g at 15 kOe.…”

“…[27], whereas, our obtained M r for BDFO bulk material is 0.118 emu/g. Again, for the same composition synthesized by chemical co-precipitation [27], the obtained maximum magnetization was 0.47 emu/g at 15 kOe. At the same level of applied field, we obtained maximum magnetization of 0.58 emu/g for BDFO bulk material.…”

“…The larger polarization in BDFO2 nanoparticles may be associated with higher leakage current, reduced electrical resistivity and hybridization of the 6s 2 lone pair electrons of Bi 3+ with the 2s/2p orbitals of O 2 [27]. As we can see, the small difference in leakage current between BDFO bulk and BDFO2…”

“…So, the BDFO bulk sample in this investigation provides superior magnetization performance compared to their corresponding nanoparticles as well as some other similar doped ceramics. To further investigate the improved magnetic properties of BDFO bulk over its nano counterparts, we compare the obtained results with results reported in [27], where Dy doped BiFeO 3 nanoparticles were synthesized by a low temperature co-precipitation method. For the 10% Dy doped BiFeO 3 nanoparticles, the reported M r value was ∼ 0.02 emu/g in Ref.…”

“…For comparison, BFO bulk ceramic material was also prepared. To further compare our findings with nanoparticles of identical composition prepared by a different synthesis technique, some results reported in [27] were considered where Dy doped BiFeO 3 nanoparticles were synthesized by a low temperature co-precipitation method. Our investigation demonstrated enhanced structural purity and multiferroic properties in Dy substituted Bi 0.9 Dy 0.1 FeO 3 bulk ceramic material compared to those of its corresponding nanoparticles and parent BiFeO 3 .…”