Energy transfer and cross-relaxation induced multicolor upconversion emissions in Er~(3+)/Tm~(3+)/Yb~(3+) doped double perovskite La_2ZnTiO_6 phosphors

Investigation on the bright and stable upconversion(UC) phosphors with multicolor emissions is fundamental and significant for the frontier applications of display and tempe rature probe.He re,dive rse emitting colors with blue,cyan and yellowish green,which are caused by the energy transfer and crossrelaxation processes,are obtained by altering Er~(3+),Tm~(3+)and Yb~(3+) concentrations in Er~(3+)singly,Er~(3+)-Tm~(3+)-Yb~(3+)co-and tri-doped double perovskite La_2 ZnTiO_6(LZT) phosphors synthesized by a simple solid-state reaction.In addition,excellent infrared emission at 801 nm located at "first biological windo w" is collected in Tm~(3+)-Yb~(3+)co-doped phosphors.Meanwhile,the temperature sensing properties based on the thermally coupled levels(~2 H_(11/2)/~4S_(3/2)) of Er~(3+) ions were analyzed from 298 to 573 K of LZT:0.15 Er~(3+)/0.10 Yb~(3+)phosphor,demonstrating that the maximal sensitivity value is about56×10-4 K~(1-) at 448 K.All these results imply that this kind of UC material has potential applications in display,bioimaging and optical device.     

The effects of oscillatory feeding of CO and O2 on the performance of a monolithic catalytic converter of automobile exhaust gas: a modelling study

A monolithic catalytic converter of automobile exhaust gas was modelled in order to assess the effects of oscillatory feeding on the performance of the reactor with respect to CO oxidation by O₂. Simulations were performed with an oscillating feed composition of CO and O₂. The influence of frequency, amplitude, phase angle and ratio of reactants in the feed on the time average CO conversion was investigated. An improvement relative to the steady state conversion of 10% maximum is obtained at temperatures below the light-off temperature, at frequencies below 0.1 Hz and an amplitude of 15%. The reverse effect is obtained from temperatures slightly above the light-off temperature upwards. These effects are strongest when CO and O₂ oscillate in counterphase. The explanation for this effect is given in terms of strongly changing surface coverage during cycling of the feed concentrations.     

Interfacial Energy Level Alignment and Defect Passivation by Using a Multifunctional Molecular for Efficient and Stable Perovskite Solar Cells

Tin oxide (SnO₂) is currently the dominating electron transport material (ETL) used in state-of-the-art perovskite solar cells (PSCs). However, there are amounts of defects distributed at the interface between ETL and perovskite to deteriorate PSC performance. Herein, a molecule bridging layer is built by incorporating 2,5-dichloroterephthalic acid (DCTPA) into the interface between the SnO₂ and perovskites to achieve better energy level alignment and superior interfacial contact. The multifunctional molecular bridging layer not only can passivate the trap states of Sn dangling bonds and oxygen vacancies resulting in improved conductivity and the electron extraction of SnO₂ but also can regulate the perovskite crystal growth and reduce defect-assisted nonradiative recombination due to its strong interaction with undercoordinated lead ions. As a result, the DCTPA-modified PSCs achieve champion power conversion efficiencies (PCEs) of 23.25% and 20.23% for an active area of 0.15 cm² device and 17.52 cm² mini-module, respectively. Moreover, the perovskite films and PSCs based on DCTPA modification show excellent long-term stability. The unencapsulated target device can maintain over 90% of the initial PCE after 1000 h under ambient air. This strategy guides design methods of molecule bridging layer at the interface between SnO₂ and perovskite to improve the performance of PSCs .     

Low temperature defect chemistry of oxides

Defect chemistry at lower temperatures, e.g. room temperature, is systematically described, at which the oxygen exchange reaction is no longer reversible. Analytical relations, numerical results, case studies as well as technological and scientific relevance are highlighted. It is pointed out that the low temperature defect chemistry also offers a quantitative basis to manipulate charge carrier and defect concentrations and related physical properties of oxide electroceramics.     

Characterization of Nd1-xSrxMnO3±δ SOFC cathode materials

The crystal structure, thermal expansion behavior and electrical conductivity of Nd_1-xSr_xMnO_3±δ (x=0–0·5) perovskite oxides were investigated. The chemical compatibility of the compositions with 40 and 50 mol% Sr with Gd₂O₃ doped CeO₂ (CGO) electrolyte was also studied. An orthorhombic GdFeO₃-type symmetry (space group Pbnm, z=4) was identified for all perovskite oxides, and the lattice parameters were determined. As the level of Sr doping increases, the pseudo-cubic lattice constant decreases, and the thermal expansion coefficient increases. The electrical conductivity can be described by the small polaron hopping conductivity model. The conductivity increases on increasing Sr doping, while the activation energy decreases. The compositions with 40 and 50 mol% Sr show very good thermal expansion and chemical compatibility with CGO electrolyte and can be considered as candidate intermediate temperature solid oxide fuel cell cathode materials.     

Complexing of NixMny sulfides microspheres via a facile solvothermal approach as advanced electrode materials with excellent charge storage performances

Mixed metal sulfides with high specific capacitances and superior rate capabilities can meet the need of new materials for technological advancement of energy storage systems. We demonstrate in this study a facile fabrication of microspheres-like Ni_xMn_y sulfides with different molar ratios of metallic salts through a one-step solvothermal route. The hierarchical Ni_xMn_y sulfides-based compounds feature spherical architectures with relatively rough surfaces and assembled from ultrasmall and self-aggregated nanoprimary crystals. Especially, the Ni_xMn_y sulfide (x/y = 1:1) presents an excellent battery-like performance with a high specific capacitance (219.4 mAh g⁻¹ at current density of 1 A g⁻¹) and a good rate capability (123 mAh g⁻¹ at 50 A g⁻¹), benefiting from the greatly improved faradaic redox processes boosted by the synergistic effect of Ni and Mn electroactive components and as well as fast mass transfer. Furthermore, the as-fabricated asymmetric supercapacitor based on Ni_xMn_y sulfide (x/y = 1:1) presents a maximum energy density of 34 W h kg⁻¹ at a power density of 868.1 W kg⁻¹ with both superior rate and long-term cycling stabilities. In view of low cost and improved electrochemical performance, such integrated compound proposes a new and feasible pathway as a potential electrode configuration for energy storage devices.     

Design of a CaAlSiN3:Eu/glass composite film: Facile synthesis,high saturation-threshold and application in high-power laser lighting

Even though CaAlSiN₃:Eu²⁺ (CASN) is, in many regards, a highly suitable red phosphor that can be used in white light-emitting diodes, it can hardly be used in high-power laser-lighting because of its low saturation-threshold. By using CASN-based composite ceramics, it is possible to increase the threshold but new difficulties appear. These include complex and expensive synthesis, while the saturation-threshold still has room for improvement. In this study, we prepare a CASN/glass composite film, using an industry-friendly blade-coating method. The film has a high internal quantum efficiency of 79%, which suggests low conversion loss. Under 1.17 W blue laser excitation, a high luminous efficacy of 21.0 lm/W can be obtained. More importantly, the composite film shows a record-high saturation-threshold of more than 12.7 W (∼320 W/cm²) blue laser excitation. With these outstanding properties, CASN/glass composite films may open doors towards commercially viable red color converters for high-power laser-lighting applications.     

Research on rapid solidification technology in Sweden

A selected programme, funded by the Swedish government agency STU, to increase knowledge of rapid solidification technology was started in 1984. Fourteen new research projects at Swedish universities and research institutes have been initiated. The article describes the aims of the programme and its organisation.