Eu3+掺杂5Li2O-1Nb2O5-5TiO2发光陶瓷的制备及性能研究

以Li2CO3、Nb2O5、TiO2和Eu2O3为原料,采用固相法制备Eu3+掺杂的5Li2CO3-1Nb2O5-5TiO2(LNT)发光介质陶瓷.通过密度、XRD和荧光光谱测试,对0.2%(质量分数)Eu2O3掺杂的陶瓷片进行性能表征.结果表明:1 120 ℃烧结致密的陶瓷片,其晶相结构为"M-相"与Li2TiO3两相复合构成;在400 nm的近紫外光激发下,样品有较强的橙光(592 nm)和红光(615 nm)发射,分别属于Eu3+的5D0→7F1的磁偶极跃迁和5D0→7F2的电偶极跃迁.     

Electromagnons in multiferroic YMn2O5 and TbMn2O5

Based on temperature dependent far infrared transmission spectra of YMn2O5 and TbMn2O5 single crystals, we report the observation of electric dipole-active magnetic excitations, or electromagnons, in these multiferroics. Electromagnons are found to be directly responsible for the steplike anomaly of the static dielectric constant at the commensurate--incommensurate magnetic transition and are the origin of the colossal magneto-dielectric effect reported in these multiferroics.     

Mixed conductivity of glasses in the P2O5-V2O5-Na2O system

The conductivity of glasses in the P₂O₅−[(1−x) V₂O₅−x Na₂O] system is studied as a function of temperature and composition. For all compositions, the conductivity variations as a function of temperature follow an Arrhenius type relationship: . The activation energies and pre-exponential factors corresponding to the V₂O₅ richest compositions are lower than that corresponding to the ionic ones. Isothermal variations of the conductivity as a function of composition show a deep minimum for a molar ratio x near 0.65. On either side of this minimum, the conductivity is mainly electronic (x<0.7) or ionic (x>0.8). The variations are interpreted assuming a prevailing diluting effect of the non predominantly present oxide without any interactions between the electronic and ionic charge carriers. Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998.     

Infrared spectra and isomeric structures of hydroxide ion-water clusters OH- (H2O)1-5: a comparison with H3O (H2O)1-5

Size-selected hydroxide ion water tetramers and pentamers [OH-(H₂O)_4,5], produced by a supersonic expansion, have been investigated using vibrational predissociation spectroscopy in conjunction with ab initio calculations based on density functional theory (DFT). The observed spectra in the frequency range 2650–3850 cm^?1 show some broad absorption bands attributed to the free and hydrogen bonded OH stretches of OH-(H₂O)_4,5 at an estimated cluster temperature of 170 K. DFT calculations performed at the B3LYP/6-31 + G* level reveal five and eight possible low lying isomeric forms for OH-(H₂O)₄ and OH-(H₂O)₅, respectively. The global minimum isomer of the tetramer is tri-solvated cyclic, which is energetically more stable than the tetra-solvated wheel-shaped form with an OH- ion at its centre. Compact cage-like lowest energy structures are found for the pentamer, in which the water molecules can act either as a single-donor-single-acceptor, as a double-proton-donor, or as a double-donor-single-acceptor in both the firs1183t a1192nd the second solvation shell of the OH- ion core. Interconversion among the isomers appears to be rapid as manifested in the observed spectra dominated by broad and congested absorptions. To understand the nature of spectral broadening and congestion, systemic comparisons of the results are made against those of the corresponding protonated cations, H+(H₂O)_n|1 and the corresponding halide anions, X-(H²O)ⁿ X = F, Cl, Br, and I. It is suggested that the spectral complexities observed for OH-(H₂O)_4,5 are predominantly a result of sampling configurations with a large distribution of O_solvent-O_ion-O_solvent angles and O_solvent … H-O_solvent distances between water molecules in the firs1175t a1181nd/or second hydration shells, together with the existence of more than one isomer in the supersonic expanson and rapid isomeric interconversion among them.     

Reactivity between CuxV2O5 and AgyV2O5 bronzes studied by spark plasma sintering

A method based on the analysis of reaction layers that form in Cu_xV₂O₅–Ag_yV₂O₅ interdiffusion couples annealed by spark plasma sintering to quickly explore the Cu–Ag–V₂O₅ ternary system at high pressure is presented. Through use of microanalysis profiling, the phases occurring in this system have been obtained much faster than by conventional techniques of solid-state chemistry. Microdiffraction profiling has also been used to properly identify the Cu_0.5Ag_0.5V₂O₅ phase in the reaction layer between CuV₂O₅ and Ag_0.8V₂O₅. The stability domains of the phases have been approximately determined and interpreted. In most cases, reaction kinetics occurs quickly, as expected by the high diffusion coefficient of Cu and Ag in V₂O₅. Though the experiments have been carried out under high pressure (75 MPa), the same phases are obtained than with sealed quartz tubes experiments.     

Mössbauer spectra and electrical conductivity ofxFe2O3−(40-x)V2O5−60P2O5 glasses

Mössbauer spectra and electrical conductivities were measured for the purpose of studying on the conduction mechanism of xFe₂O₃?(40-x)V₂O₅?60P₂O₅ glasses. The ratios Fe²⁺/Fe²⁺+Fe³⁺ in xFe₂O₃?(40-x)V₂O₅?60P₂O₅ glasses were determined by Mössbauer spectroscopy. On the composition dependence of D. C. conductivities in these glasses, the minimum of log σ at each temperature was obtained at 25Fe₂O₃?15V₂O₅?60P₂O₅. The conductivities of ternary glassses in Fe rich region could be explained only by the changes of carrler (Fe²⁺) concentration and the hopping conduction between Fe²⁺ ions and Fe³⁺ ions in binary glasses. In V rich region, the saturation tendency of D. C. conductivities are observed. It was suggested to be explained by increasing of V⁴⁺ ions due to the influence of Fe ions.     

Spin-Flop Transition in Co2B2O5 Pyroborate

JETP Letters - Recent theoretical ideas concerning the mechanism of the electromagnetic proximity effect in hybrid superconducting structures with ferromagnetic layers, as well as the problem of...