Nanoscale LuFeO₃: shape dependent ortho/hexa-phase constitution and nanogenerator application

Abstract

Ferroelectric and nanogenerator response of ortho and hexa-mixed phase LuFeO3 nanoparticles and nanofibers embedded in a PDMS matrix.

Unusual magnetic ordering transitions in nanoscale biphasic LuFeO3: the role of the ortho–hexa phase ratio and the local structure

“…It is reported that, while the oxidation states do not change, the spectra are sensitive to the changes in the local environments of the Fe 3+ and Lu 3+ sites in the h-and o-structures. We have also recently reported strain-stabilization of different proportions of -o and -h phases in LuFeO3 nanoparticle and nanofiber systems 7 and its consequences for extraordinary polarization and nanogenerator properties. In this work we examine the consequences of the co-existence of o-LFO and h-LFO phases in different proportions in two different nanoscale morphologies i.e.…”

“…We also observed that while going from NP to NF, the Pbnm phase undergoes an increase in strain while the P63cm unit cell slightly relaxes. 7 This shows that the growth model for individual cases of NPs and NFs is quite different from that of the thin film growth model. 5 Based on the observed angles between the (112) planes of the hexagonal and orthorhombic phases in the TEM images, the two phases are seen to be interfaced at φ such that 90°< φ<120°.…”

“…This is an extraordinary material, which exhibits both orthorhombic (o-) and hexagonal (h-) structures. [5][6][7] There is a significant difference in lattice symmetry and coordination of Fe ion in the case of these o-and h-structures. In o-LFO, ferroelectricity is unexpected due to the symmetry of lattice; while a canting of Fe moments towards c-direction gives rise to weak ferromagnetism below the Neel Temperature (620 K).…”

“…24 For the synthesis of LFO-NF electrospinning technique was used as discussed previously. 7 The NPs and NFs were annealed up to the temperature just below the temperature of forming the pure orthorhombic phase, to assess the stability of hexagonal phase in different morphologies. In addition to different standard materials characterizations, the investigation of local structure around the transition metal ion (Fe 3+ ) was performed by the X-ray Absorption Near Edge Structure (XANES) which reveals the variation of the local structure as the symmetry of the Fe ion changes.…”

“…27 Since free energy of formation of o-LuFeO3 is lower than that of h-LuFeO3, this favours the formation of hexagonal phase on the orthorhombic phase to cross the energy barrier over the length scale of submicrometer. 6,7 Table 1. Observed Raman modes in the present study and their one to one comparison with the reported Raman modes for orthorhombic and hexagonal phases, alongwith their designation.…”