Effects of Pr dopant on grain boundary and electrical properties of Ce5.2Sm0.8MoO15-delta

Material formulated as Ce5.2Sm0.8-xPrxMo15-(delta) (x=0.08) was prepared by adding small amounts of Pr dopant in oxide Ce5.2SM0.8-xPrxMoO15-delta. Structural and electrical properties were investigated by means of X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM) and AC impedance spectroscopy. The effect of small amounts of Pr on microstructure and electrical conductivity was discussed. It was showed that the material doped with Pr has a lot of dents and small openings, which provide channels for oxygen ions, resulting in lower grain boundary and total conductivity activation energy. Thus the corresponding grain boundary conductivity and total conductivity of the material were improved notably. The grain boundary conductivity of the material doped with Pr is 6.79 X 10(-3) S center dot cm(-1) at 500 degrees C, which is twice as large as that without Pr (5.61 X 10(-5) S center dot cm(-1)).

Synthesis and electrical properties of new solid state. Electrolyte materials Ce5.2RE0.8MoO15-delta

A series of solid state electrolytes, Ce-5.2 RE0.8 MoO15-delta (RE = Y, La, Sm, Gd, Dy, Ho, Er), were synthesized by sol-gel method. Their structures and electrical conductivities were characterized by X-ray Diffraction (XRD), Raman and X-ray Photoelectron Spectroscopy (XPS) and AC impedance spectroscopy, respectively. The results show that the concentrations of oxygen vacancy increased with increasing x and their conductivity were improved. And the cell parameters increase as the radius of RE3+ increases. Because the ionic radius of doped Dy3+ (0.0908 nm) is closed to that of Ce4+ (0.0920 nm), their oxide has minimal cell elastic straining between RE3+ and oxygen vacancy, and the system has the least association enthalpy, thus the oxide Ce-5.2 Dy-0.8 MoO15-delta exhibits a higher conductivity (7.02 x 10(-3) S/cm) and lower activation energy (1.056 eV) compared to the other doped compounds.

Synthesis, characterization and electrical properties of solid state electrolyte materials La2-xCaxMo1.7W0.3O9-delta (0 <= x <= 0.2)

The new compounds La2-xCaxMo1.7W0.3O9-delta (0 <= x <= 0.2) in which La3+ substituted with Ca2+ were synthesized by dry-chemistry techniques based on the oxygen Ionic conductor La2Mo1.7W0.3O9. The new series were characterized by X-ray Diffraction (XRD), Raman and X-ray Photoelectron Spectroscopy (XPS) and the electrical conductivity of samples were investigated by AC impedance spectroscopy. The lattice parameters were reduced due to the smaller atomic radius of the Ca2+ compared with that of the La3+. Furthermore, Additional oxygen vacancies were introduced into La2Mo1.7W0.3O9 lattice by substitution, and then the oxygen ionic conductivity was increased. At 550 degrees C, the conductivity increased 89.9%, that is, from 0.79 x 10(-4) S center dot cm(-1) (x=0) to 1.5 X 10(-4)S center dot cm(-1) (x=0.16, 0.2).

Preparation, structure and oxide ion conductivity in Ce6-xYxMoO15-delta (x=0.1-1.4) solid solutions

The Ce6-xYxMoO15-delta solid solution with fluorite-related structure have been characterized by differential thermal analysis/thermogravimetry (DTA/TG), X-ray diffraction (XRD), IR, Raman, scanning electric microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods. The electric conductivity of samples is investigated by Ac impedance spectroscopy. An essentially pure oxide-ion conductivity of the oxygen-deficiency was observed in pure argon, oxygen and air. The highest oxygen-ion conductivity was found in Ce5.5Y0.5MoO15-delta ranging from 5.9 X 10(-5)(S cm(-1)) at 300 degrees C to 1.3 X 10(-2)(S cm(-1)) at 650 degrees C, respectively. The oxide-ion conductivities remained stable over 80 h-long test at 800 degrees C. These properties suggested that significant oxide-ionic conductivity exists in these materials at moderately elevated temperatures.

Facilitated ion-transfer of sodium cation by (anthraquinone-1-yloxy) methane-15-crown-5 across the water/1,2-dichloroethane microinterface

The transfer of sodium cation facilitated by (anthraquinone-1-yloxy) methane-15-crown-5(L) has been investigated at the water/1,2-dichloroethane microinterface supported at the tip of a micropipette. The diffusion coefficient of (anthraquinone-1-yloxy) methane-15-crown-5 obtained was (3.42 +/- 0.20) x 10(-6) cm(2) s(-1). The steady-state voltammograms were observed for forward and backward scans due to sodium ion transfer facilitated by L with 1:1 stoichiometry. The mechanism corresponded to an interfacial complexation (TIC) and interfacial dissociation (TID) process. The association constant was calculated to be log beta(o) = 11.08 +/- 0.03 in the DCE phase. The association constant of other alkali metals (Li+, K+, Rb+) were also obtained.

Low threshold amplified spontaneous emission based on coumarin 151 encapsulated in mesoporous SBA-15

Amplified spontaneous emission (ASE) characteristics of a blue dye coumarin 151 encapsulated in a highly ordered mesoporous SBA-15 were studied. The spectra narrowing was observed and found that the threshold and loss were greatly reduced, and the gain is significantly increased compared with spin-coated coumarin 151 doped poly(4-vinylphenol) film. The ASE threshold, gain, and loss, respectively, reached 0.55 mJ pulse(-1) cm(-2), 44.78 cm(-1), and 8.9 cm(-1) for the coumarin 151 encapsulated in mesoporous SBA-15 film. The optimized lasing action owes much to the effects of the better spatial confinement of the molecules in the ordered mesoporous structure of the host SBA-15.

Covalent linking of near-infrared luminescent ternary lanthanide (Er3+, Nd3+, Yb3+) complexes on functionalized mesoporous MCM-41 and SBA-15

The near-infrared (NIR) luminescent lanthanide ions, such as Er(III), Nd(III), and Yb(III), have been paid much attention for the potential use in the optical communications or laser systems. For the first time, the NIR-luminescent Ln(dbm)(3)phen complexes have been covalently bonded to the ordered mesoporous materials MCM-41 and SBA-15 via a functionalized phen group phen-Si (phen-Si = 5-(N,N-bis-3-(triethoxysilyl)propyl)ureyl-1,10-phenanthroline; dbm = dibenzoylmethanate; Ln = Er, Nd, Yb). The synthesis parameters X = 12 and Y = 6 h (X denotes Ln(dbM)(3)(H2O)(2)/phen-MCM-41 molar ratio or Ln(dbM)(3)(H2O)(2)/phenSBA-15 molar ratio and Y is the reaction time for the ligand exchange reaction; phen-MCM-41 and phenSBA-15 are phen-functionalized MCM-41 and SBA-15 mesoporous materials, respectively) were selected through a systematic and comparative study. The derivative materials, denoted as Ln(dbM)(3)phen-MCM-41 and Ln(dbm)(3)phen-SBA-15 (Ln = Er, Nd, Yb), were characterized by powder X-ray diffraction, nitrogen adsorption/desorption, Fourier transform infrared (FT-IR), elemental analysis, and fluorescence spectra. Upon excitation of the ligands absorption bands, all these materials show the characteristic NIR luminescence of the corresponding lanthanide ions through the intramolecular energy transfer from the ligands to the lanthanide ions.

An investigation of low-field magnetoresistance in the double perovskites Sr2Fe1-xZnxMoO6, x=0, 0.05, 0.15 and 0.25

The electrical, magnetic and transport properties of Zn doped polycrystalline samples of Sr2Fe1-xZnxMoO6 ( x = 0, 0.05, 0.15 and 0.25) with the double perovskite structure have been investigated. The subtle replacement of Fe3+ ions by Zn2+ ions facilitates the formation of a more ordered structure, while further substitution leads to disordered structure because of the presence of a striped phase. Analysis of the x-ray powder diffraction patterns based on Rietveld analysis indicates that the replacement of Fe3+ by Zn2+ ions favours the formation of Mo6+ ions. The spin-glass behaviour can be explained on the basis of the competition between the antiferromagnetic superexchange and the ferromagnetic double-exchange interaction. The low-field magnetoresistance was moderately enhanced at x = 0.05, and its origin was found to be the competition between the decrease of the concentration of the itinerant electrons and the weaker antiferromagnetic superexchange in the antiphase boundaries. An almost linear negative magnetoresistance in moderate field has been observed for x = 0.25. A possible double-exchange mechanism is proposed for elucidating the observations; it also suggests a coexistence of (Fe3+, Mo5+) and (Zn2+, Mo6+) valence pairs.

Mechanisms of sodium and potassium ions transfer facilitated by dibenzo-15-crown-5 across the water /1,2-dichloroethane interface using micropipettes

The transfer of sodium and potassium ions facilitated by dibenzo-15-crown-5 (DB15C5) has been studied at the micro-water/1,2-dichloroethane (water/DCE) interface supported at the tip of a micropipette. Cyclic volt-ammetric measurements were performed in two limiting conditions: the bulk concentration of Na+ or K+ in the aqueous phase is much higher than that of DB15C5 in the organic phase (DB15C5 diffusion controlled process) and the reverse condition (metal ion diffusion controlled process). The mechanisms of the facilitated Na+ transfer by DB15C5 are both transfer by interfacial complexation (TIC) with 1 : 1 stoichiometry under these two conditions, and the corresponding association constants were determined at log beta(1) = 8.97 +/- 0.05 or log beta(1) = 8.63 +/- 0.03. However, the transfers of K+ facilitated by DB15C5 show different behavior. In the former case it is a TIC process and its stoichiometry is 1 : 2, whereas in the latter case two peaks during the forward scan were observed, the first of which was confirmed as the formation of K (DB15C5)(2) at the interface by a TIC mechanism, while the second one may be another TIC process with 1 : 1 stoichiometry in the more positive potential. The relevant association constants calculated for the complexed ion, K+(DB15C5)(2), in the organic phase in two cases, logbeta(2), are 13.64 +/- 0.03 and 11.34 +/- 0.24, respectively.