The Effect of Substituting Ga for Alon Crystal Structure of Phosphors MAl 2Si2O8: Eu2+ (M= Ca, Sr, Ba)

A series of luminescence phosphors M0.955Al2 –xGaxSi2O8∶Eu2+ (M=Ca, Sr, Ba, x = 0~1.0) were prepared via solid-state reaction in weak reductive atmosphere. The lattice positions were discussed. It was found that when Ga3+ entered MAl2Si2O8 lattice and substituted Al3+, complete solid solutions formed. The lattice parameters (a, b, c) and unit cell volume of phosphors M 0.955Al2 –xGaxSi2O8: Eu2+ (M=Ca, Sr, Ba, x = 0~1.0) increased linearly, the lattice parameters (α, β,γ) of Ca0.955Al2–xGaxSi2O8∶Eu2+(CAS) decreased linearly and the lattice parameter β of Sr0.955Al2–xGaxSi2O8∶Eu2+(SAS) and Ba0.955Al2–xGaxSi2O8∶Eu2+(BAS) increased linearly as Ga3+ content increased.

Effects of Mg Doping at Different Positions in Li-Rich Mn-Based Cathode Material on Electrochemical Performance

Li-rich Mn-based layered oxides are among the most promising cathode materials for next-generation lithium-ion batteries, yet they suffer from capacity fading and voltage decay during cycling. The electrochemical performance of the material can be improved by doping with Mg. However, the effect of Mg doping at different positions (lithium or transition metals) remains unclear. Li1.2Mn0.54Ni0.13Co0.13O2 (LR) was synthesized by coprecipitation followed by a solid-state reaction. The coprecipitation stage was used to introduce Mg in TM layers (sample LR-Mg), and the solid-state reaction (st) was used to dope Mg in Li layers (LR-Mg(st)). The presence of magnesium at different positions was confirmed by XRD, XPS, and electrochemical studies. The investigations have shown that the introduction of Mg in TM layers is preferable in terms of the electrochemical performance. The sample doped with Mg at the TM positions shows better cyclability and higher discharge capacity than the undoped sample. The poor electrochemical properties of the sample doped with Mg at Li positions are due to the kinetic hindrance of oxidation of the manganese-containing species formed after activation of the Li2MnO3 component of the composite oxide. The oxide LR-Mg(st) demonstrates the lowest lithium-ion diffusion coefficient and the greatest polarization resistance compared to LR and LR-Mg.

Expeditious Base-free Solid-State Reaction between Phenyl Boronates and Hydrogen Peroxide on Silica Gel

The conversion of phenyl boronates to phenol by hydrogen peroxide (H2O2) usually requires the base as the chemical assistant. In this work, we reported a base-free reaction between the phenyl...

Dramatic impact of the TiO2 polymorph on the electrical properties of ‘stoichiometric’ Na0.5Bi0.5TiO3 ceramics prepared by solid-state reaction

Bulk conductivity (σb) values of nominally stoichiometric Na0.5Bi0.5TiO3 (NBT) prepared by solid-state reaction collated from literature show random variation between 10-6 -10-3 S cm-1 (at 600 °C). This makes it...

Ultrahigh Permittivity, Ultralow Loss and Stability in (In0.5Ta0.5)0.1Ti0.9O2 Ceramics With Temperature Range From -100 to 235 °C

Dielectric materials with excellent dielectric properties are being promoted in requirements of microelectronic devices. In this study, (In0.5Ta0.5)0.1Ti0.9O2 ceramics were achieved by a solid-state reaction with reducing atmosphere of N2. Also, dense microstructure, ultrahigh permittivity (εr = 1.18 × 105) and ultralow dielectric loss (tanδ = 0.0072) were demonstrated at1 kHz. Interestingly enough, the temperature coefficient of permittivity which satisfies X9D (-100 °C - 235 °C, Δεr/ε25°C < ± 3.3 %) maintained stability at 1 kHz, and the dielectric mechanism could be connected to the electron-pinned defect dipoles (EPDD), which has favourable potential applications in electronic devices.