Search

Control of Eu valence is one of the main issues to obtain mixed−valent Eu2+/3+ co−doped phosphor with flexible−tunable emission spectra. In this study, for the first time, we report a simple single cation substitution strategy for controlling Eu valence. The structure of Sr1−xBaxAl2Si2O8 host was tailored by Ba2+ substitution for Sr2+ ions. The lattice parameters show a linear evolution with increase in Ba2+ amount. Correspondingly, the Eu3+ emission intensity also increases over Ba2+ amount. The spectral variation was considered to be attributed to the suppression of Eu3+ reduction by the lattice stress, which is introduced by ion substitution. Finally, valence control of Eu and spectral tuning of Eu3+/2+ co−doped Sr1−xBaxAl2Si2O8 phosphor were realized by the proposed strategy. This study will open a novel avenue for Eu valence control and spectral tuning of mixed–valent Eu doped phosphors.

Tin sulfide (SnS), a typical IV–VI compound with low-cost, abundant-earth and eco-friendly elements, has aroused widespread attentions in the thermoelectric community due to its similar electron and phonon structures with SnSe. However, undoped SnS possesses the features of low carrier concentration and inferior band structures, which produces indecent thermoelectric performance. In this work, we successfully resolved these shortcomings of SnS through stepwise Na doping and Se alloying. Firstly, the carrier concentration of SnS was increased and optimized through Na doping, which leads to an enhancement both in electrical conductivity and Seebeck coefficients through activating multiple valance bands. Secondly, the electronic band structure of SnS was modified through Se alloying, both narrowing band gap and flatting valence band shape contribute excellent electrical transport properties, resulting in maximum power factor ∼6.0 μWcm−1K−2. After synergistically optimizing interdependent thermoelectric parameters through Na doping and Se alloying, a record high ZT of 0.70 at 873 K was obtained in polycrystalline SnS. Our work indicates that SnS is one of very promising earth-abundant thermoelectric materials for power generation in mediate-temperature range.

Crystal structure tailoring is a commonly used method for tuning the luminescence of phosphors. This study mainly aims at luminescent spectra tuning of Sr1−xBaxAl2Si2O8:Eu2+ phosphors by substitution of Ba for Sr ions. The phase composition was characterized by X-ray powder diffraction and the crystal structure was determined by using the Rietveld refinement method. The excitation and emission spectra, diffuse reflectance spectra, and thermal quenching were also investigated in detail. The results show that Sr1−xBaxAl2Si2O8:Eu2+ phosphors can form a series of continuous solid solutions in the range from 0 to 0.75. With the increase in x value, the emission spectra show an obvious redshift from 415 to 450 nm. The emission redshift plays an important role in enabling Sr1−xBaxAl2Si2O8:Eu2+ to be used as a standard blue phosphor for application in white-light-emitting diodes.

In 2 TiO 5 is the only ternary oxide in the In–Ti–O phase diagram. It was prepared by high temperature solid state reaction in this work and verified to be pure with high crystallinity by Le Bail fitting on the powder X-ray diffraction (XRD) pattern. Scanning electron microscopy show that the micrometer particles of In 2 TiO 5 was composed of submicron crystallites. UV–vis diffused reflectance spectra suggested a wide bandgap of 3.55 eV, which is consistent with the theoretical calculations. The bottom of the conduction band is composed of both In 6s and Ti 3d orbitals, however the low density of the states lead to a low density of the charge carriers excited by UV irradiation. Thus the photocatalytic H 2 production rate of In 2 TiO 5 is only 3.6 μmol/h/g in 20 vol% methanol aqueous solution. With the assistance of Ru- and Pt-cocatalyst, the activity is significantly increased and the optimal H 2 evolution rate is 35.7 μmol/h/g when loading 1 wt% Ru and 1 wt% Pt, simultaneously. All the catalysts recovered after the photocatalytic reactions show no degradation according to powder XRD.