•Li or Ag doped Sr2MgSi2O7-based phosphor prepared by solid state reaction method.•The doping of Li+ ions induced an increase of phosphorescent intensity by 1.5 times.•The mechanism of Sr2MgSi2O7: Eu2+, Dy3+, R+ (R+ = Li+, Ag+) enhancement discussed.Long afterglow phosphor Sr2MgSi2O7: Eu2+, Dy3+ doped with R+ (R+ = Li+, Ag+, respectively) was synthesized by the high temperature solid-state reaction method. Crystal structure, morphological and luminescent properties were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL), decay curves and thermoluminescence (TL) curves. The results indicate that the incorporation of these metal ions has no influence on the position of the emission peak which is determined by the 4f7→4f65d1 Eu2+ ions, but has influence on the intensity of the emission and the afterglow. The highest phosphorescent intensity was observed with 2.5 mol% of Li+, and 0.4 mol% of Ag+ doping in respectively. Compared with the undoped sample, the optimum incorporation of Li+ ions could induce a remarkable increase of phosphorescent intensity and the decay constant by about 1.5 times and 1.6 times, respectively. Doping Ag+ ions can also improve the luminescence properties, but the performance is not good as Li+ ions. The mechanism of Sr2MgSi2O7: Eu2+, Dy3+, R+ (R+ = Li+, Ag+, respectively) enhancement has been discussed.

•F-doped LiFePO4/C is first synthesized using a co-precipitation method.•The hydrofluoric acid source with low cost is first adopted as F source.•F doping can impact the intrinsic and extrinsic properties of LiFePO4/C.•F doping can achieve 126.0 and 107.4 mAh g−1 at 20, 30C after 50 cycles.•F-doped LiFePO4/C shows distinctive advantage than ones prepared by other methods.F-doped LiFePO4/C materials were first synthesized using a co-precipitation method followed by high-temperature treatment with hydrofluoric acid source. The structure, morphology, valence state and electrochemical performance of F-doped LiFePO4/C materials are investigated systematically. The structure analysis shows that the introduction of F alters the lattice parameters slightly, increases the lattice volume, and changes the interatomic distances. The morphology analysis indicates that the particle size of F-doped LiFePO4/C samples are slightly increased compared with LiFePO4/C sample, F doping promotes the growth of the primary particles. An interesting red shift in FTIR analysis shows that F doping induces the rearrangement of the electron cloud in the PO43−, thus impacts the intrinsic conductivity and enhances the electrochemical performance. Raman analysis reveals that the LiFePO4/C and F-doped LiFePO4/C composites almost have the same amount of sp2-coordinated carbon in the residual carbon, thus F doping is more critical to the electrochemical performance compared with the carbon coating. XPS analysis shows that F is successfully incorporated into the product, and F doping does not change the valance of elements. Therefore, F doping impacts the above intrinsic and extrinsic properties of LiFePO4/C, and those changes will significantly influence the electrochemical performance. The electrochemical analyses show that the F-doped LiFePO4/C samples perform a better high rate performance and cycling life compared with the undoped LiFePO4/C composites. Especially, the LiFePO4−xFx/C (x = 0.15) sample performs the most remarkable high rate performance and an excellent cycling life and capacity retention, the discharge capacities are 165.7, 161.1, 155.3, 150.8, 140.3, 129.8 and 115.7 mAh·g−1 at 0.1, 1, 3, 5, 10, 20 and 30 C rates, respectively. F doping can improve the inherent demerits of LiFePO4 materials, enhance the electronic conductivity, accelerate the Li+ ions diffusion coefficient, and improve the structure stability.

Microwave-assisted synthesis of electrode materials for lithium-ion batteries has drawn extensive attention owing to the unique microwave dielectric heating. In this work, olivine LiFePO4 hexagonal nanoplates, with a short b-axis, were successfully synthesized using a single-mode microwave-assisted hydrothermal system at 160 °C just in 20 min. Microwave irradiation can lower the synthesis temperature and shorten the synthesis time dramatically. The growth process of LiFePO4 hexagonal nanoplates with microwave irradiation time was investigated. The role of electromagnetic field in the formation and the quality of the resulting LiFePO4 were explored. In order to enhance the electrochemical properties of LiFePO4 hexagonal nanoplates, LiFePO4/C and LiFePO4/rGO have been obtained through surface decoration of LiFePO4 nanoplates by ex situ carbon coating and in situ reduced graphene oxide (rGO) coating. The electrochemical analysis demonstrated that LiFePO4/rGO had more excellent electrochemical performance; the initial discharge capacity at 0.1 C was up to 167.2 mAh g−1 which was very close to the theoretical value (170 mAh g−1). This is because the in situ coating can achieve a complete coating of the surface and rGO has a higher electrical conductivity. The rGO layer can boost the transport speed of the lithium ions and electrons, and reduce the charge transfer resistance of Li ion insertion/extraction. Furthermore, the unique structure of the nanoplates with a short b-axis is favored to shorten the migration of Li+ ion.

ZnO single crystal microtubes have been successfully synthesized using direct microwave irradiation via the catalyst-free vapor–solid (V–S) process. Field emission scanning electron microscopy (FE-SEM) showed that ZnO single crystal microtubes exhibit a symmetrical 6-facet structure with an exact hexagonal hollow. ZnO single crystal microtubes have an average outer diameter of 100 µm and a length of over 300 µm, and the wall thickness ranges from 1 to 2 µm. X-ray diffraction (XRD) reveals a single high-intensity diffraction peak along the (101) direction, suggesting good crystallization of the synthesized ZnO single crystal microtubes. Single crystal diffraction (SCD) reveals the obvious polar nature of the ZnO single crystal microtube structure. The room-temperature photoluminescence (PL) spectrum shows an intense ultraviolet (UV) emission at 375.68 nm, with weak and broad visible light emissions in the range between 435 nm and 700 nm at a maximum peak of 588.66 nm.

•ZnO microtube length of 650–700 μm, diameter of 50 μm, wall thickness of 1–3 μm•ZnO microtube possesses a single crystal wurtzite hexagonal structure.•The crystal system is hexahedral oriented along a-axis with indices of (100).•A strong and sharp UV emission at 375.89 nm (3.29 eV)•One prominent absorption band around 378.88 nm (3.27 eV)Morphological, structural, and optical characterization of microwave synthesized ZnO single crystal microtubes were investigated in this work. The structure and morphology of the ZnO microtubes are characterized using X-ray diffraction (XRD), single crystal diffraction (SCD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The results reveal that the as-synthesized ZnO microtube has a highly regular hexagonal cross section and smooth surfaces with an average length of 650–700 μm, an average outer diameter of 50 μm and wall thickness of 1–3 μm, possessing a single crystal wurtzite hexagonal structure. Optical properties of ZnO single crystal microtubes were investigated by photoluminescence (PL) and ultraviolet-visible (UV-vis) absorption techniques. Room-temperature PL spectrum of the microtube reveal a strong UV emission peak at around 375.89 nm and broad and a weak visible emission with a main peak identified at 577 nm, which was assigned to the nearest band-edge emission and the deep-level emission, respectively. The band gap energy of ZnO microtube was found to be 3.27 eV.

•Zn1−xMgxO (x = 0%, 2% and 5%) microtubes were successfully synthesized within 20 min.•Zn1−xMgxO microtubes wavelength peak shifting from the UV to the visible region.•ZnO microtube with Eg = 3.27 eV while for Zn0.95Mg0.05O microtube is 3.35 eV.•The intensity of UV emission peak decreased with increase of MgO concentration.•Blue shift from 538 nm for ZnO microtube to 529 nm for Zn0.95Mg0.05O microtube.The Zn1−xMgxO (x = 0%, 2% and 5%) microtubes have been successfully synthesized via a microwave heating method. The as synthesized microtubes were carefully investigated. Field emission scanning electron microscope (FE-SEM) showed that all the microtubes exhibit an exact hexagonal hollow structure with smooth surfaces and straight characteristics throughout their whole lengths. UV–Vis measurement indicates that the absorption peak for ZnO microtube was shifted from 378.88 nm (3.27 eV) to 369.91 nm (3.35 eV) for Zn0.95Mg0.05O microtube. Room temperature photoluminescence (PL) spectra showed that the intensity of UV emission peak decreased with increase of MgO concentration and the visible emission band showed a blue shift from 538.06812 nm for ZnO microtube to 529.54114 nm for Zn0.95Mg0.05O microtube. Energy-dispersive spectrometer (EDS) analysis revealed the presence of Zn and O as the only elementary components with the absence of MgO as a doping material.

Single mode microwave assisted synthesis of Lithium iron phosphate using iron carbonyl complex [Fe2(CO)9], as source of iron is reported in this paper. The suitable synthesis method for the LiFePO4 was designed based on FT-IR and TG-DTA studies of precursors. As prepared samples were characterized using different techniques such as X-ray diffraction, scanning electron microscope, field emission scanning electron microscope, transmission electron microscope, thermo gravimetric analysis, Raman spectroscope and electrochemical measurements. X-ray diffraction revealed that a single phase LiFePO4 powder can be synthesized quickly and easily by microwave processing. The surface analysis of the as prepared samples reveal that, it consist of nano-size particles with porous agglomeration, where the pores serve as channel for lithium supply and assist for augmentation of the electrochemical character of the product. The initial discharge capacities are 154.2, 132.2 and 121mAhg−1 at 0.1 C, 0.5 C and1 C rate respectively. The obtained LiFePO4 has a high electrochemical capacity and good cyclic ability even after 50 cycles, which is attributed to the smaller particle size, porous agglomeration and graphitic carbon content.

ZnO sub-millimeter crystals were synthesized by microwave heating from ZnO powders without any catalyst or transport agent. Zinc oxide raw materials were evaporated from the high-temperature zone in an enclosure and crystals were grown on the self-source substrate. The thermodynamics analysis method was used to estimate the partial pressure of gases in the chamber, which shows that the pressure of ZnO could be neglected entirely in the range of experiment temperature. The kinetics analysis was employed to estimate the growth rate in different conditions, which shows a remarkable temperature gradient and a high system temperature would enhance the growth rate. Optics photos reveal that these products are hexagon crystals with 0.2–0.3 mm in diameter and 0.5–1 mm in length. A vapor-solid mechanism is proposed to explain the growth process of ZnO crystals. The temperature distribution in microwave oven is mainly determined by properties of electric field and it is different from that of a conventional method.

Porous Mn-doped LiFePO4/C cathode material was synthesized by facile and fast microwave assisted solid state reaction from iron carbonyl complex using citric acid as reducing agent and source of carbon. The microstructure and electrochemical performance were systematically investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), field emission scanning electron microscope (FE–SEM), transmission electron microscope (TEM), Raman spectroscopy, charge–discharge cycling, cyclic voltammogram and electrochemical impedance spectroscopy. It was found that the as-prepared composites have a single phase of orthorhombic olivine-type structure and Mn2+ has successfully introduced into the M2(Fe) sites. The electrochemical properties of LiFe0.99Mn0.01PO4/C were compared with bare LiFePO4 and LiFePO4/C composite prepared by identical route. Compare to as-prepared LiFePO4/C composites, LiFe0.99Mn0.01PO4/C demonstrates a remarkable electrochemical property in terms of discharge capacity, electrochemical reversibility and cycling performance with an initial discharge capacity of 163.2 mAh g−1 at a discharge rate of 0.1 C. It also performed excellent even at higher current densities. The improved electrochemical performance was attributed to the smaller particle size, porosity, the enhancement of the P–O bond and the facilitation of Li+ ion “effective” diffusion, induced by Mn2+-substitution.