Yuki Inami

Bio: Yuki Inami is an academic researcher from Meijo University. The author has contributed to research in topics: Powder diffraction & Crystal structure. The author has an hindex of 1, co-authored 2 publications receiving 15 citations.

Synthesis and ferroelectric properties of bismuth layer-structured (Bi7−xSrx)(Fe3−xTi3+x)O21 solid solutions

Abstract: Bismuth layer-structured (Bi 7− x Sr x )(Fe 3− x Ti 3+ x )O 21 (BSFT) ceramics were synthesized and the ferroelectric properties and crystal structure were investigated. X-ray powder diffraction profiles and refinement of the lattice parameters indicated single phase BSFT was obtained in the composition range 0–1.5. The lattice parameter b of BSFT remained almost constant, while a slight decrease in the lattice parameter a was observed by the Sr and Ti substitution for Bi and Fe, respectively, which indicated an increase in the orthorhombicity. The dependence of the BSFT lattice parameter on temperature implied a phase transition from the orthorhombic to the tetragonal phase, which was in good agreement with the Curie temperature. The remnant polarization P r , of BSFT was significantly improved by the Sr and Ti substitution for Bi and Fe, and ranged from 9 to 16 μC/cm 2 , although no remarkable variation in the coercive field E c was observed. As a result, a well-saturated P – E hysteresis loop of BSFT ceramic was obtained at x =0.5 with a P r of 30 μC/cm at an applied voltage of 280 kV/cm.

Synthesis of Ni-substituted Bi7Fe3Ti3O21 ceramics and their superior room temperature multiferroic properties

Abstract: Layer-structured bismuth complex oxides Bi7Fe3−xNixTi3O21 (0 ≤ x ≤ 2) (BFNT) were synthesized using a low-temperature combustion synthesis method. X-ray diffraction patterns and high-resolution transmission electron microscopy analysis indicated that the samples presented a six-layer Aurivillius structure. Substituting Fe sites by Ni ions inside the lattice was found to be effective in enhancing the multiferroic properties at or above the room-temperature. The sample with a composition of x = 1 exhibited a large remnant magnetization (2Mr = 1.32 emu g−1) that is about five hundred times higher than that in un-substituted Bi7Fe3Ti3O21 ceramics. The work is an important step in the effort to find a single phase and a fully functioning multiferroic material.

Structural Evolution and Multiferroics in Sr-Doped Bi7Fe1.5Co1.5Ti3O21 Ceramics

Abstract: The ceramics with the composition of SrxBi7−xFe1.5Co1.5Ti3O21−δ (0 ≤ x ≤ 1, SBFCT) were prepared by a citrate–nitrate combustion method, and the phase evolution with an increasing Sr content was investigated. Pure Aurivillius phase SBFCT with a layer number of n = 6 was obtained when x ≤ 0.25, and then the structure collapsed to 5 layers for x = 0.50, then alternating 4 and 5 layers for x = 0.75, and finally 4 layers for x = 1.00. Meanwhile, secondary phase Sr1−mBimFe1−iCoiO3−γ appeared when x > 0.25, which is antiferromagnetic (AFM) and with low resistivity. Enhanced ferromagnetic and ferroelectric properties were observed from single phase SBFCTs at the room temperature, and the ferromagnetic transition temperature (Tc) increases with the Sr doping level x in the single phase range. The remnant magnetization (2Mr) is 2.27 emu/g and the remnant polarization (2Pr) is 2.89 μC/cm2 at an applied electric field of 100 kV/cm for the x = 0.25 sample.

Structural transformation and multiferroic properties in Gd-doped Bi7Fe3Ti3O21 ceramics

Abstract: Bismuth layer-structured Bi7−xGdxFe3Ti3O21 (0.00 ≤ x ≤ 1.50) ceramics were synthesized by Pechini's method, in which gadolinium doping was used with a goal to enhance the magnetic response of the material. With increase in the Gd content of x, an obvious structural transformation, changing gradually from the originally designed six-layer structure to five-layers, was initially shown by X-ray diffraction patterns, and then by Raman scattering spectra and high-resolution transmission electron microscopy images. Substituting Bi sites with Gd3+ ions was found to be able to effectively suppress the leakage current, and its resistivity was found to be about two orders of magnitude higher than that of the un-doped sample. Improved magnetic properties and a clear magnetic anomaly were observed in the sample with a composition of x = 1.00, indicating the behaviour of transforming from anti-ferromagnetism with weak ferromagnetism at the room temperature into a complex magnetism at low temperature.

Progress and Perspectives on Aurivillius-Type Layered Ferroelectric Oxides in Binary Bi4Ti3O12-BiFeO3 System for Multifunctional Applications

Abstract: Driven by potentially photo-electro-magnetic functionality, Bi-containing Aurivillius-type oxides of binary Bi4Ti3O12-BiFeO3 system with a general formula of Bin+1Fen−3Ti3O3n+3, typically in a naturally layered perovskite-related structure, have attracted increasing research interest, especially in the last twenty years. Benefiting from highly structural tolerance and simultaneous electric dipole and magnetic ordering at room temperature, these Aurivillius-phase oxides as potentially single-phase and room-temperature multiferroic materials can accommodate many different cations and exhibit a rich spectrum of properties. In this review, firstly, we discussed the characteristics of Aurivillius-phase layered structure and recent progress in the field of synthesis of such materials with various architectures. Secondly, we summarized recent strategies to improve ferroelectric and magnetic properties, consisting of chemical modification, interface engineering, oxyhalide derivatives and morphology controlling. Thirdly, we highlighted some research hotspots on magnetoelectric effect, catalytic activity, microwave absorption, and photovoltaic effect for promising applications. Finally, we provided an updated overview on the understanding and also highlighting of the existing issues that hinder further development of the multifunctional Bin+1Fen−3Ti3O3n+3 materials.