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In this work, the low-temperature phase MnBi prepared by a low-temperature vacuum sintering process at 325 °C was studied. We found a significant increase in the energy product from 2.63 MGOe in the 12-h sintered sample to 3.64 MGOe in the 48-h sintered sample. This improvement is attributed to the solid-liquid diffusion process. Cross-sectional scanning electron microscopy (SEM) reveals that MnBi forms at the external surface of Mn particles and along interior surfaces, notably within cracks. Transmission electron microscopy further demonstrates that the Mn ratio increases and Bi decreases with distance from the crack. The selected area diffraction showed variations in the Mn ratio with distance from cracks and identified both Bi and MnBi phases in the MnBi layer. Magnetic force microscopy (MFM) analysis exhibited large phase shifts indicating repulsive or attractive forces in single ferromagnetic domains. This provides valuable insight into magnetic domains in the MnBi regions near Mn cracks. The MnBi formation model, developed for the vicinity of single cracks with uniform MnBi content, partly explains the magnetic interactions and phase shifts observed near these cracks. These findings provide significant insights into the MnBi microstructural and magnetic properties, potentially useful in tailoring and engineering magnetic structures. • Low-temperature vacuum sintering increased (BH) max of the MnBi from 2.63 to 3.64 MGOe due to the diffusion process. • Cross-sectional SEM and TEM revealed MnBi formation near cracks, with the presence of both Bi and MnBi phases. • MFM revealed significant phase shifts, indicating magnetic interactions within ferromagnetic domains in MnBi regions. • The MnBi formation model successfully explained the observed MFM signals and magnetic interactions. [ABSTRACT FROM AUTHOR]

Electrical conductance measured from across or parallel to a {110} symmetrical grain boundary in SrTiO 3 is considerably lower than the ones of the adjoined (100) grains and a SrTiO 3 (100) single crystal, but these differences are decreased significantly upon UV irradiation. Based on ultraviolet photoelectron spectroscopy and complementary conductive atomic force microscopy, we demonstrate that the hundredfold increases in the electrical conductance measured at the grain boundary are strongly associated with the ultraviolet-induced oxygen vacancies. Our results reveal the possibility of tuning the oxygen vacancies and electrical conductance at the grain boundary simply by UV irradiation, offering novel strategies for optoelectronic applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Low-temperature phase manganese bismuth (LTP-MnBi) and a series of aluminum (Al) composites were synthesized using a potentially facile and scalable low-temperature liquid-phase sintering method in a vacuum at 300 °C. The incorporation of up to 10 at% Al led to a significant enhancement in coercivity (H c), increasing from 2.32 ± 0.04 to 4.15 ± 0.07 kOe, while saturation magnetization showed a slight decrease of less than 3 %. However, beyond this concentration, a dramatic reduction in H c was observed. The density of the freshly compacted powders, which included up to 10 at% Al, remained relatively constant at 7.47–7.58 g/cm³ but decreased with excess Al. A maximum energy product (BH) max of 1 MGOe was achieved in the fresh sample, with a 16 % enhancement in (BH) max in the MnBi composite containing 5 at% Al. Scanning electron microscopy revealed distinct MnBi and Bi-rich regions, while Al-rich areas became prominent at Al concentrations above 10 at%. Energy dispersive spectroscopy confirmed that only 3–5 at% Al could be effectively incorporated into Mn-Bi regions, with excess Al unevenly distributed on the surface. X-ray photoelectron spectroscopy indicated the formation of Al, Al₂O₃, and potential Mn-Bi-Al ternary alloys. Additionally, slab-DFT models, such as AlMn/MnBi, indicate that Al inclusion enhances the magnetization in MnBi composites, providing insights into its effects on the magnetic properties of Mn-Bi systems. These findings offer promising strategies to address the challenges posed by excess Bi in the MnBi structure, potentially optimizing the magnetic performance of similar non-magnetic or soft-magnetic composite systems. [Display omitted] • Large-scale synthesis of MnBi can be achieved through sintering in a vacuum. • An increase of up to 16 % in (BH) max was observed in MnBi with 5 at% Al composites. • 3–5% Al interacts with the MnBi phase, with excess forming an Al-rich phase. • The formation of Mn-Bi-Al ternary alloys was confirmed by XPS analysis. • The AlMn/MnBi slab-DFT model shows enhanced MnBi magnetization with Al inclusion. [ABSTRACT FROM AUTHOR]

Nitrogen- and co-nitrogen- and sulfur-doped reduced graphene oxide (named N-rGO and N/S-rGO) was prepared by a simple hydrothermal technique using urea and thiourea as doping agents, respectively, to improve the properties of supercapacitor electrodes. Both were compared with rGO in electrochemical evaluations. The supercapacitor using N-rGO in 1 M H 2 SO 4 provided the largest specific capacitance, 99 F g−1, while those using N/S-rGO and rGO exhibited 51 and 19 F g−1 at 0.25 A g−1, respectively. Furthermore, the supercapacitors using N-rGO and N/S-rGO electrodes showed a smaller charge transfer resistance (R ct) and a lower IR -drop than those using the rGO electrode, indicating a faster charge transfer at the interface between electrode and electrolyte and higher electronic conductivity due to N or N/S heteroatom doping in the graphene oxide structure. Furthermore, the N-rGO electrode has a higher sp2 hybridization ratio and a lower I D /I G ratio than the N/S-rGO electrode. Furthermore, the lowest contact angles of the N/S-rGO electrode were found, which was attributed to better aqueous electrolyte compatibility than the N-rGO and rGO electrodes. Therefore, the higher electrical conductivity of the N-rGO electrode reveals more relevant characteristics for high-performance supercapacitors than the good wettability of the N/S-rGO electrode. • N- and N/S-doping rGO can improve the conductivity and wettability of electrodes. • N- and N/S-doped rGO demonstrates a reduction in the sp2 hybridization ratio and an increase in I D /I G. • The specific capacitance of N-rGO is greater than that of N/S-rGO and rGO. • The cycle stability of N-rGO is superior to that of N/S-rGO and rGO. [ABSTRACT FROM AUTHOR]

Due to 2nd-order Jahn-Teller effect, some M cations such as Ti4+, Sn4+, In3+, Nb5+, Cu2+ and W6+ are allowed to enter the MO 6 octahedral site while maintaining the high-symmetry structure of MTe 3 O 8. Therefore, the series of MTe 3 O 8 compounds when M = Sn, Ti, In 0·5 Nb 0·45 V 0.05 and In 0·4 Cu 0·1 Nb 0·4 W 0.1 were successfully synthesized. Rietveld refinement is utilized to visualize the crystal structures. M − O bonds are expanded because of the larger M cations while the O-M-O angles are distorted slightly. As a result of stereoactive 5 s 2 lone-pair electron of Te4+ in TeO 4 E unit, the structure is flexible as reflected by the small variation of Te–O bond lengths and O–Te–O angles. XANES reveal that the local structures of all compounds are preserved. However, different M cations affect their color and electronic band structures, which can be explained differently by the simple band-to-band transition, the VB-V 3 d electronic transition and the d-d electronic transition. [Display omitted] • In 0·5 Nb 0·45 V 0·05 Te 3 O 8 and In 0·4 Cu 0·1 Nb 0·4 W 0·1 Te 3 O 8 were first studied. • Both short-range and long-range orderings are preserved in all compounds. • XANES and XPS spectra are investigated in detail. • The effects of M cations on electronic structures and optical properties are discussed. [ABSTRACT FROM AUTHOR]