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Color-tunable and white-emitting Pr3+ and Tb3+ co-doped La2Ti2O7 phosphors were prepared via a molten salt method. The as-synthesized samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflection spectra (DRS), photoluminescence spectra (PL), fluorescence decay curves and temperature-dependent photoluminescence spectra in detail. The La2Ti2O7:Pr3+, Tb3+ phosphors are uniform square-like nanobelt and the band gap of La2Ti2O7 host is calculated to be 3.83 eV by DRS. Under 296 nm wavelength UV excitation, the La2Ti2O7:Pr3+ compounds show strong red emission with peaking at 612 nm. Four typical emission lines of Tb3+ ions are observed from the region of 480–650 nm in La2Ti2O7:Tb3+ phosphors, and the strongest green emission peak is located at 545 nm. What's more, the emission color of La2Ti2O7:0.001Pr3+, 0.010 Tb3+ can be tuned from white (0.3274, 0.3379) to pink (0.4777, 0.2890) upon the excitation from 290 to 348 nm and the emission color of La2Ti2O7:0.001Pr3+, xTb3+ can be also tuned from white to green by changing the concentration of Tb3+. The La2Ti2O7:Pr3+, Tb3+ phosphors have the poor temperature dependence, resulting from the value of ΔR (the displacement between parabolas of the intervalence charge transfer states and ground states) for Tb3+ and Pr3+ both are larger. The results indicate that La2Ti2O7:Pr3+, Tb3+ phosphors could be a promising tunable and white light emission phosphor.

Exploring the process of structure evolution and mechanism of controllable luminescence in the solid solution phosphors is meaningful but still challenging. Herein, new solid solution phosphors of Ca9Al1-xYx(PO4)7:Eu2+ were selected as examples to address the challenging via the construction of bi-directional relationships between structure evolution and photoluminescence property. In Ca9Al1-xYx(PO4)7, the structure evolution caused the redistribution of Eu2+ in the multiple cationic sites, accompanied by the changes of emission color from blue (0.1828, 0.1192) to cyan (0.1723, 0.3305), which were investigated by Gaussian fitting, decay time, and bond energy theory. Conversely, the Gaussian fitting peaks displayed different blue or red shifts in the process of structure evolution, which could reversely reflect the specific changes of bond lengths in each cationic site and were helpful for exhaustive understanding the process of structure evolution in Ca9Al1-xYx(PO4)7. Besides, the thermal stability behaviors of Ca8.95Al1-xYx(PO4)7:0.05Eu2+ exhibited that the decline rate of low energy bands were faster than that of high energy bands due to the thermally active phonon-assisted effect. The constructed bi-directional relationships pave a feasible way to investigate the variations of structure evolution and emission properties, which will be helpful for the design of new kinds of phosphors.

Single-phase multiferroic hexaferrite Sr3Co2Fe21.6O37.4 was prepared by using a conventional solid-state reaction. The maximum electric polarization and magnetoelectric coefficient were Pm = 12.8 μC/m2 and αm = 600 ps/m, respectively. We found that the as-prepared specimen exhibited four different electric phase states from 0 to 1 T. Furthermore, the magnetic field and electric field poled the specimen's four different electric phase states and exhibited four different magnetoelectric effects. Based on these characteristics, a nonvolatile four-state memory device was implemented at room temperature. The information is written by the magnetic field and electric field in the poling process and read out by αm with a small scanning field. This kind of nonvolatile four-state memory device has the benefits of having a simple structure and high storage density, it is easy to integrate, and it can be performed at room temperature. Our work enriched the magnetoelectric effect of Sr3Co2Fe24O41 and will promote the application of multiferroic hexaferrites for information storage devices.

Crystallographically c-axis textured Zn2W barium ferrites (i.e., BaMe2Fe16O27), synthesized by traditional ceramic methods, are presented as a high-magnetic-remanence material for self-biased microwave and millimeter wave applications. A magnetic field orientation process was applied to obtain c-axis texture of ferrite materials while sintering parameters were systematically optimized to obtain high-performance materials for self-biased circulators and isolators. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to confirm structure, crystal orientation, and microstructural morphology of the Zn2W ferrite final product. Room temperature vibrating-sample magnetometry (VSM) was applied to measure hysteresis (M vs. H) loops that provided an evaluation of coercivity (Hc), magnetization (M), and magnetic remanence (Mr) and squareness ratio (Mr/Ms). The ferrite samples sintered at 1020 °C demonstrated excellent magnetic properties, such as high squareness ratio (∼0.8), relative density (89% of theoretical), 4πMS ∼ 3115 Gauss, and coercive fields of ∼1011 Oe.

The effects of Cu substitution for Ni atoms on the magnetic and magnetocaloric properties have been investigated in Mn0.8Fe0.2Ni1-xCuxGe (x = 0.05–0.3) compounds. The substitution of Cu leads to the larger separation of Mn atoms, which stabilizes the hexagonal phase and thus reduces the structural transition temperature Tstr. Moreover, the larger separation of nearest-neighbor Mn atoms weakens the ferromagnetic (FM) coupling in TiNiSi-type orthorhombic phase and results in the spiral antiferromagnetic (AFM) and more antiparallel AFM state with increasing Cu content. Similarly, the Ni2In-type hexagonal phase also changes from FM state to weak-magnetic spin-glass-like state with the introduction of Cu. The x = 0.05 compound shows a conventional magnetocaloric effect (MCE) due to the magnetostructural transformation from PM hexagonal phase to FM orthorhombic phase. On the contrary, the x = 0.1 compound undergoes the antiferromagnetically magnetostructural transition from FM hexagonal phase to AFM orthorhombic phase, which leads to a high inverse MCE. This large inverse MCE could be utilized in novel magnetic refrigerator to improve the refrigeration efficiency and applied for magnetic refrigeration of natural gas liquefaction.

The hot tensile tests of Ti-6Al-4V alloy sheet at different temperatures (650, 700, 750 ℃) and different strain rates (0.1 s−1, 0.01 s−1, 0.001 s−1) were carried out, five phenomenological models are established (Arrhenius with strain compensation(ARR), Johnson-Cook(JC), modified JC(m-JC), Hensel-Spittel(HS), modify HS(m-HS)). A new JC model considers the softening coefficient m as a function of strain rate and adds a temperature correction function is proposed. The electron backscatter diffraction (EBSD) test was used to observe the microstructure evolution after thermal deformation at 700 ℃-0.1 s−1. After high-temperature tensile loading, the proportion of β phase increased, the average grain size decreased by 67.69%. The macroscopic softening phenomenon is caused by dynamic recrystallization (DRX), dynamic recovery (DRV), and the formation of β phase. The prediction accuracy of the six models was discussed by comparing the AARE value and the R-value. The comparison results show that the HS model has the best prediction accuracy, and its AARE value and R-value are 5.24% and 0.98794; the JC model has the worst prediction ability, and its AARE value and R-value are 41.1% and 0.84726. The prediction accuracy of the n-JC model is higher than that of the other JC models.

Novel single-phased and emission-tunable layered Bi4Ti3O12:Pr3+ nanosheets have been successfully synthesized via molten salt method. The as-prepared samples were characterized by X-ray diffraction and scanning electron microscopy to investigate their crystalline phases and morphologies. Furthermore, we explored the photoluminescence properties of the Bi4Ti3O12:Pr3+ phosphors, while the cross-relaxation processes between 1D2, 3P0 emitting states and the Pr3+–Ti4+ intervalence charge transfer state, color tuning and thermally stability were discussed in detail. Besides, the emission hue of Bi4Ti3O12:Pr3+ could be adjusted from white-light (0.3059, 0.2731) to yellow (0.5167, 0.4792) by tuning the excitation wavelength, in which the ratio of 3P0→3H4 and 1D2→3H4 was changed. In addition, the increases in temperatures led to the cooperative effects of thermal-quenching behavior and the cross-relaxation processes, thus resulting in the significant decrease of 3P0→3H4 emission in comparison to the 1D2→3H4 emission. The results suggested that the Bi4Ti3O12:Pr3+ is an effective color-tuning phosphor.

In this paper we report BiFeO3-Bi2Fe4O9 composite with negative permittivity at about 1 GHz, a necessary step to construct a real metamaterial with both negative permeability and negative permittivity. This purposely designed material is obtained by a self-assembly procedure with the same starting raw material. The composite material shows a dielectric resonance at about 1 GHz. The reason for the resonance is analyzed, based on the equivalent resistance-inductance-capacitance circuit, which is confirmed through the theoretical model. Furthermore, the frequency of the resonance can be easily tuned by varying the composition ratio. Our results show that the composite is applicable in the new field of metamaterials for the miniaturization of antennas.

CuIn(S,Se)2 (CISS) powders with varying S/[S + Se] ratios were synthesized by mechanochemical process (MCP) and a self -propagating combustion occurred during milling. Influence of S content on the structure was investigated by X-ray diffraction and Raman spectroscopy. Morphology of CISS powders was investigated by scanning electron microscopy (SEM). Characteristic peaks of the chalcopyrite structure are clearly observed and CISS (112) peaks shifts to higher value as S content was increased. Lattice constants for CISS samples decrease with the S content increased. Moreover, the large size mismatch between S and Se atoms leads to the lattice parameters negative deviate from Vegard's law. The Raman A1 mode of the chalcopyrite CISS has been observed, and InxSey and CuS has been also detected in some samples. The morphology observation of CISS powders shows that the uniformity of particle size distribution decreases with increasing sulfur content. The ignition time of Cu-In-S-Se self-propagating reaction was extended with the increase of sulfur content and the possible reason has been explained. Furthermore, the reaction mechanism of Cu-In-S-Se system has also been discussed.

A three-dimensional (3D) BiOClxBr1-x (x = 0–1) solid solutions nanostructures with compositional tunability were successfully synthesized via a one-step glycol-assisted hydrothermal process in the presence of cationic polyacrylamide (C-PAM) and cetyltrimethylammonium bromide (CTAB). The prepared samples displayed hierarchical flower-like microspheres with rich in specific surface area and appropriate pore size, providing suitable pathways for transportation and separation of photogenerated electrons and holes. The controllable ratio of Cl− and Br− led to the decrease in the optical bandgap, thus increasing the absorption of visible light range. The solid solutions delivered remarkable adsorption capacity and photocatalytic activity in comparison with pure BiOCl, BiOBr and P25 (TiO2 nanoparticles) in the photodegradation of methyl orange (MO) aqueous solution under visible light irradiation, and the degradation rate reached the maximum at x = 0.5 and decreased gradually with x moving away from 0.5. The BiOCl0.5Br0.5 sample displayed high photostability under repeated visible light irradiation, which is especially important for its practical application. Based on the above findings, the reasonable formation mechanism and the main active species of the samples were also discussed in detail.

The anatase branched open-ended titanium dioxide (TiO 2 ) nanotubes (NTs) are prepared using a combined method of electrospinning, hydrothermal processing and calcination. The branched open-ended TiO 2 NT (BOTNT) is composed a trunk of a large sized NT, from which out growth many branches consisting of single-crystalline TiO 2 nanosheets (NSs) and small NTs. The morphology and microstructure of the BOTNTs can be controlled by varying with the hydrothermal treatment time. When it is used in flexible dye-sensitized solar cells (FDSSCs) as multifunctional layer covering on the carbon nanotubes (CNTs) incorporated TiO 2 (CNTs/TiO 2 ) nanorods (NRs) layer, a high conversion efficiency of 4.70% is obtained. This efficiency is much higher than that of the cell assembled by the single-layer CNTs/TiO 2 NRs film. This is attributed to the great increase in light harvesting efficiency, resulting from excellent light-scattering ability and high specific surface area for dye loading of the BOTNTs. Furthermore, the excellent electron transport ability of the BOTNTs due to their high level of interconnectivity, improves the performance of FDSSCs.