New Aurivillius phase Bi9Fe4.7Me0.3Ti3O27(Me = Fe, Co, Ni, Mn) oxides have been prepared using a citrate combustion method. X-ray diffraction on powders and high-resolution transmission electron microscopy investigation confirmed that the Bi9Fe4.7Me0.3Ti3O27 samples are with an eight-layer structure. Both ferromagnetic and ferroelectric investigations suggested that Co or Ni substitution could enhance their multiferroic properties,while Mn substitution depressed them. Among all the samples, Bi9Fe4.7Co0.3Ti3O27 sample exhibits the largest remnant polarization of Pr*3.8 l C/cm2, and the largest remnant magnetization of Mr*0.06 lB/f.u. with a Curie temperature about 764 K, while the Bi9Fe4.7Ni0.3Ti3O27 sample has the largest spontaneous magnetization(0.26 lB/f.u.). The improved ferromagnetic properties ofboth Bi9Fe4.7Co0.3Ti3O27 and Bi9Fe4.7Ni0.3Ti3O27 can be ascribed to the spin canting of magnetic ion-based sublattices via the Dzyaloshinskii–Moriya interaction and also the magnetic ions exchanging interactions(Fe3–O–Co3or Fe3–O–Ni3).
Guopeng WangShujie SunYan HuangJianlin WangRanran PengZhengping FuYalin Lu
CuIn（S,Se）2 thin films were prepared by thermal crystallization of co-sputtered Cu-In alloy precursors in S/Se atmosphere. In-depth compositional uniformity is an important prereq- uisite for obtaining device-quality CuIn（S,Se）2 absorber thin films. In order to figure out the influence of heat treatments on in-depth composition uniformity of CuIn（S,Se）2 thin films, two kinds of reaction temperature profiles were investigated. One process is ＂one step profile＂, referring to formation of CuIn（S,Se）2 thin films just at elevated temperature （e.g. 500 ℃）. The other is ＂two step profile＂, which allows for slow diffusion of S and Se elements into the alloy precursors at a low temperature before the formation and re-crystallization of CuIn（S,Se）2 thin films at higher temperature （e.g. first 250 ℃ then 500 ℃）. X-ray diffrac- tion studies reveal that there is a discrepancy in the shape of （112） peak. Samples annealed with ＂one step profile＂ have splits on （112） peaks, while samples annealed with ＂two step profile＂ have relatively symmetrical （112） peaks. Grazing incident X-ray diffraction and en- ergy dispersive spectrum measurements of samples successively etched in bromine methanol show that CuIn（S,Se）2 thin films have better in-depth composition uniformity after ＂two step profile＂ annealing. The reaction mechanism during the two thermal processing was also investigated by X-ray diffraction and Raman spectra.
By using first principles calculations, four two-dimensional B-C-N ternary sheets with ordered and uniform element distribution are predicted based on the C, B, or N filled g-C3N4 sheet. These B-C-N ternary sheets are metallic except for B4-C3N4 monolayer, which is a semiconductor with an energy band gap of 1.18 eV. In particular, the BnC-C3N4 is a ferromagnetic metal with a net magnetic moment of 0.57 μB/cell, which can be used to develop metal-free spintronic device. The calculated formation energy indicates these B-C-N ternary sheets are highly thermal stable. It presents a new route to obtain uniform B-C-N ternary sheet for electronic and spintronic applications.
Solid oxide fuel cells(SOFCs) have been attracting remarkable attention as one of the most promising green energy conversion devices in the recent years.However,a high susceptibility of commonly used Ni-based anodes to carbon coking is a major challenge to the successful commercialization of SOFCs.In this study,a robust anode with Ni/TiO 2-δ nano-network interfaces is reported,for low-cost SOFCs working at intermediate temperatures.This anode demonstrates an acceptable power density,and good stability with humidified(3% H2O) methane.X-ray diffraction(XRD) Rietveld refinement,X-ray photoelectron spectroscopy(XPS),electron paramagnetic resonance(EPR),and high resolution transmission electron microscopy(HRTEM) images reveal that the Ni/Ti O2-δ network-composite anode forms from the in-situ reductive decomposition of NiT iO 3.Numerous Ni/TiO 2-δ interfaces that facilitate the water adsorption and the water-mediated carbon-removing reactions form during this decomposition process.Density functional theory calculations predict that at the Ni/TiO 2-δ interfaces,the dissociated OH from H2O(adsorbed on TiO 2-δ) reacts with C(locating on Ni) to produce CO and H species,which are then electrochemically oxidized(combined with O2-) to CO2 and H2 O at the triple-phase boundaries of the anode.
The assertion that a new material could become a potential single-phase and room-temperature functioning multiferroic material may be confounded by the presence of minor amount of secondary magnetic inclusions, especially in the Aurivilliustype material system. In this study, we demonstrated that the derivative thermo-magneto-gravimetry(DTMG) technique can be a sensitive tool to identify an d quantify the magnetic secondary phases in the Bi7Fe2.25Co0.75Ti3O21 ceramic, which shows the potential to become a single-phase multiferroic material. The accuracy of this DTMG measurement experimentally reaches to ~0.5 wt.%, far below the detection limit of the traditional X-ray diffraction. The impurity identified in the specimen is the ferrimagnetic Co Fe2O4 spinel phase with an amount of ~3.6 wt.%. Significantly, the room-temperature intrinsic magnetism of the ceramic was measured, which is sorely from the main phase.
