[Show abstract][Hide abstract] ABSTRACT: Alkaline earth metal doped tin oxide (SnO2) hollow nanospheres with a diameter of 50 nm have been synthesized successfully via a facial solvothermal route in a very simple system composed of only ethanol, acetic acid, SnCl4·5H2O and A(NO3)2·xH2O (A = Mg, Ca, Sr, Ba). The synthesized undoped SnO2 and A-doped SnO2 hollow nanospheres were characterized by the oxygen storage capacity (OSC), X-ray diffraction, transmission electron microscopy and the Brunauer–Emmet–Teller (BET) technique. The OSC values of all samples were measured using thermogravimetric-differential thermal analysis. The incorporation of alkaline earth metal ion into tin oxide greatly enhanced the thermal stability and OSC. Especially, Ba-doped SnO2 hollow nanospheres calcined at 1000 °C for 20 h with a BET surface area of 61 m2 g−1 exhibited the considerably high OSC of 457 μmol-O g−1 and good thermal stability. Alkaline earth metal doped tin oxide has the potential to be a novel oxygen storage material.
Materials Research Bulletin 09/2015; 69. DOI:10.1016/j.materresbull.2014.11.018 · 2.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The band gaps of isostructural Bi2OS2 and LaOBiS2 were examined using optical
absorption and discussed with the band structures calculated based on the
crystal structures determined using synchrotron X-ray diffraction. The Bi 6p
and S 3p orbitals in the Bi-S plane were computationally predicted to
constitute the bands near the Fermi level. The optical reflectance spectra of
Bi2OS2 and LaOBiS2 showed optical band gaps of ca. 1.0 eV, which were close to
the computationally calculated direct band gaps of ca. 0.8 eV. Our results show
that Bi2OS2 and LaOBiS2 are semiconductors containing direct band gaps of
0.8-1.0 eV, and they are suggested to be candidates for optoelectronic
materials in the near-infrared region without highly toxic elements.
[Show abstract][Hide abstract] ABSTRACT: A novel photocatalyst consisting of an intercalated perovskite H1-2xPtxLaNb2O7 was fabricated by ion exchange. Synchrotron X-ray diffraction and X-ray photoelectron spectroscopy results confirmed that Pt(2+) exists within the interlayer space of the layered perovskite. H1-2xPtxLaNb2O7 composed of layered niobate perovskite and intercalated Pt(2+) completely degraded a 20 ppm phenol solution in 3 h under irradiation by Xe light, which exhibits photocatalytic activity superior to those of RbLaNb2O7, Pt-deposited RbLaNb2O7, and HLaNb2O7. From first principles density functional theory simulation, high photocatalytic activity of H1-2xPtxLaNb2O7 is attributed to the emergence of a new O 2p-Pt 5d hybridized band in top of the valence band.
[Show abstract][Hide abstract] ABSTRACT: Two new cadmium bismuthates, CdBi2O6 and Cd0.37Bi0.63O1.79, were prepared by hydrothermal reaction using NaBiO3·nH2O as one of the starting compounds. The crystal structures of these compounds were refined by using synchrotron X-ray powder diffraction data. The former bismuthate has a MnSb2O6-type structure with a hexagonal cell (space group: P321); the cell parameters were a = 9.3641(7) and c = 4.9523(3) Å, and the final R-factors were Rwp = 4.59% and Rp = 3.04%. The latter bismuthate has a fluorite-type structure with a cubic cell (space group: ) of a = 5.4110(4) Å, and the final R-factors were Rwp = 4.79% and Rp = 3.57%. These new bismuthates exhibit no photocatalytic activity under visible light.
[Show abstract][Hide abstract] ABSTRACT: Single crystals of Cu(In,Ga)S2 were successfully grown using CsCl flux in vacuum. The grown single crystals were typically 3–4 mm with unshaped form. The Cu(In,Ga)S2 single crystals with various Ga concentration were obtained by control of the Ga concentration in the starting materials. The optical band-gaps of obtained single crystals were estimated from the reflectance spectrum. The optical band-gap changed between 1.42 and 2.40 eV at room temperature with dependence on the Ga concentration.
[Show abstract][Hide abstract] ABSTRACT: The crystal structures of Ce(O,F)BiS2 synthesized from starting materials with five different F contents were determined by single-crystal X-ray analysis. An increase in F content in the starting materials slightly increased F incorporation in the grown single crystals. The grown crystals with various F contents showed similar layered structures, but minor structural changes were observed with different conductive and magnetic properties. Crystals grown from higher F content were found to have a nearly flat Bi-S plane and elongated Ce-(O,F) bond, and showed superconductive transition below similar to 3 K and spontaneous magnetization below similar to 7 K. The calculated density of states based on this structural analysis predicted that hybridized Bi 6p-S 3p orbitals intersect the Fermi level and that Ce states are located near the Fermi level. The effect of structural change on superconductivity and long-range magnetic ordering has been discussed.
[Show abstract][Hide abstract] ABSTRACT: We report on the low-temperature synthesis of submicron-sized Cu3N powder produced from CuO and NaNH2 powder mixture by heating at 150–190 °C in a Teflon-sealed autoclave. The structure was the anti-RuO3 type with a lattice parameter of 0.3814(1) nm, and strong optical absorption was observed below ∼1.9 eV. This synthesis method has the potential of facile control of the reaction with less use of ammonia sources.
[Show abstract][Hide abstract] ABSTRACT: A layered perovskite was fluorinated by polytetrafluoroethylene (PTFE) and then exfoliated to prepare a solution of fluorinated-perovskite nanosheets. Dion-Jacobson-type layered perovskites, RbLaNb2O7 and KCa2Nb3O10, were prepared in solid-state reactions at 950 and 1100 degrees C, respectively. The perovskites were fluorinated using PTFE at 400 degrees C, upon which their color changed from white to gray or black and their electrical conductivity increased to the order of 10(-4)-10(-5) S/m. The tetrabutyl ammonium cations(TBA(+)) in each fluorinated layered perovskite were first intercalated by tetrabutylammonium hydroxide(TBAOH) in H2O and then exfoliated in an acetonitrile solution for electrodeposition. Aniline was added to the solution as a monomer and electrodeposition was carried out in the acetonitrile solution for formation of a hybrid film. X-ray diffraction patterns confirmed that the polyaniline molecules could be intercalated within the interlayer space. Despite the fluorination, the volumetric filling fractions of polyaniline in the interlayer space were around 0.4 and 0.2 for the respective samples from RbLaNb2O7 and KCa2Nb3O10. The electrochemical specific capacitances of the deposited hybrid films increased steeply from below 50 F/g to above 230-250 F/g owing to the fluorination.
Colloids and Surfaces A Physicochemical and Engineering Aspects 10/2014; 459:186–193. DOI:10.1016/j.colsurfa.2014.07.001 · 2.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Co-Al and Ni-Al layered double hydroxides (LDHs) intercalated with three types of anionic molecules, dodecylsulfate (C12H25SO4−, DS), di-2-ethylsulfosuccinate ([COOC2H3EtBu]2C2H3SO3−, D2ES), and polytungstate (H2W12O4210−, HWO) were prepared by means of ion-exchange and co-precipitation processes. With the use of DS and D2ES as intercalation agents, high crystallinity was maintained after intercalation into the LDHs. In the case of HWO, the intercalated LDHs could be obtained by ion-exchange as well as co-precipitation with a decline in the crystallinity; however, unreacted LDH was detected in the ion-exchange samples, and some unwanted phases such as hydroxide and pyrochlore were generated by the co-precipitation process. The maximum specific surface area and pore volume of the Ni-Al sample with intercalated HWO, prepared by the ion-exchange process were 74 m2/g and 0.174 mL g−1, respectively. The occupancies of DS, D2ES, and HWO within the interlayer space were approximately 0.3–0.4, 0.5–0.6, and 0.1–0.2, respectively, in the Co-Al and Ni-Al LDHs. Analysis of the catalytic activity demonstrated that the DS-intercalated Ni-Al LDH sample exhibited relatively good catalytic activity for conversion of cyclohexanol to cyclohexanone.
[Show abstract][Hide abstract] ABSTRACT: The crystal structures of a pentavalent bismuthate, SrBi2O6 with the PbSb2O6-type structure and a lead bismuth oxide, (Pb1/3Bi2/3)O1.4 with the fluorite-type structure were refined by using neutron diffraction data. The final R-factors were Rwp = 4.49, Rp = 3.46, RI = 4.50 and RF = 1.70% for SrBi2O6 and Rwp = 5.04, Rp = 3.93, RI = 5.47 and RF = 4.26% for (Pb1/3Bi2/3)O1.4. SrBi2O6 prepared from NaBiO3·1.4H2O is the first example of the bismuthate with the PbSb2O6-type structure. The fluorite-type lead bismuth oxide, (Pb1/3Bi2/3)O1.4 was obtained by heating the PbSb2O6-type lead bismuthate, PbBi2O5.9·H2O which was prepared also from NaBiO3·1.4H2O.
[Show abstract][Hide abstract] ABSTRACT: Two new pentavalent bismuthates, CaBi2O6-x·1. 1H2O and PbBi2O6-x·H2O were prepared from NaBiO3·nH2O. Broadened X-ray powder diffraction patterns for both bismuthates were indexed to the hexagonal cell observed for PbSb2O6-type SrBi2O6. The lattice parameters were a = 0.555(1) and c = 0.530(1)nm for CaBi 2O6-x·1.1H2O and a = 0.5544(4) and c = 0.531(1) nm for PbBi2O6-x·H2O. At elevated temperatures, the Ca derivative decomposed to Ca3Bi 8O15 and an unknown phase via the fluoritetype structure, whereas the Pb derivative changed to Pb1/3Bi2/3O 4/3 via the fluorite-type (Pb1/3Bi2/3)O 1.4. Both Ca and Pb derivatives exhibited photocatalytic activity for the decomposition of phenol under visible light irradiation, although the adsorption of phenol was observed under dark conditions. The fluorite-type phases evolved from the Ca and Pb derivatives did not adsorb phenol under dark conditions, and their photocatalytic activities toward phenol decomposition under visible light were inferior to those of the parent compounds.
Journal- Ceramic Society Japan 06/2014; 122(1426):509-512. DOI:10.2109/jcersj2.122.509 · 0.85 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The crystal structures of FexWN2 (x similar to 0.74, 0.90) and their magnetic properties were investigated. The structural studies reveal the formation of ion defects with different concentrations in the two-dimensional iron triangular lattice by analyzing the synchrotron radiation X-ray diffraction data. The magnetic measurements demonstrate that the Fe0.74WN2 phase shows ferromagnetism at 300 K, while the less defective Fe0.90WN2 phase exhibits no ferromagnetism. A decrease of temperature to 5 K significantly suppresses the room-temperature ferromagnetism of the Fe0.74WN2 phase. We attribute the emergence of ferromagnetism in FexWN2 to the increases of defect concentration and thermal displacement in the iron triangular lattice.
Journal of Alloys and Compounds 04/2014; 593:154–157. DOI:10.1016/j.jallcom.2014.01.030 · 2.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Spinel-type LiTi2O4 was prepared directly by the reaction of lepidocrocite-type potassium titanate and molten LiCl at 750-850 degrees C in a stream of H-2 gas. The Li/Ti ratio in the spinel-type phase prepared at 850 degrees C was 0.54, and the lattice parameter and superconductive critical temperature T-c were alpha = 8.3935(2) angstrom and 12.3 K, respectively. The product at 750 degrees C exhibited no superconductive diamagnetism down to 2.5 K, and the product at 800 C showed weak superconductive diamagnetism at 10.5 K. The morphology of the particles prepared at 850 degrees C showed an irregular shape with a particle size of 1-10 mu m.
Journal- Ceramic Society Japan 04/2014; 122(1424):307-309. DOI:10.2109/jcersj2.122.307 · 0.85 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Perovskite-type structures (ABO3 ) have received significant attention because of their crystallographic aspects and physical properties, but there has been no clear evidence of a superconductor with a double-perovskite-type structure, whose different elements occupy A and/or B sites in ordered ways. In this report, hydrothermal synthesis at 220 °C produced a new superconductor with an A-site-ordered double perovskite structure, (Na0.25 K0.45 )(Ba1.00 )3 (Bi1.00 )4 O12 , with a maximum Tc of about 27 K.
[Show abstract][Hide abstract] ABSTRACT: The crystal structures of superconducting LaO1-xFxBiS2 (x ~ 0.23, 0.46) were
determined by single-crystal X-ray diffraction analysis. Their space group was
P4/nmm. Distortion of the Bi-S plane changed when the F content was increased
from 0.23 to 0.46, and a nearly flat Bi-S plane was formed at x ~ 0.46.
Computational calculations supported this effect of F doping on distortion of
Bi-S plane. Computational predictions suggested that LaO1-xFxBiS2 with higher F
contents were thermodynamically more unstable under ambient pressure. We
discussed the bonding, conductivities, and synthetic routes of LaO1-xFxBiS2.
Journal of Solid State Chemistry 01/2014; 212. DOI:10.1016/j.jssc.2014.01.035 · 2.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We examined the effect of polymer polytetrafluoroethylene ( PTFE) additive on the growth of InN crystals by the nitridation of LiInO2 in NaNH2 flux at 240 degrees C. LiInO2 and NaNH2 powder were heated with/without PTFE pieces in a steel crucible located inside the PTFE-lined autoclave. The additive of PTFE pieces enhanced the decomposition of LiInO2 with the mass loss of these pieces and progressed the formation of InN and In(OH)(3) byproducts. SEM and TEM images of the products using PTFE additives showed the hexagonal InN crystals of similar to 1 mu m in size, and the optical bandgap of synthesized InN was estimated as similar to 2.03 eV. We presume that fluorine in PTFE additive subtracts Li from LiInO2 and enhances the growth of InN crystals.
Journal- Ceramic Society Japan 01/2014; 122(1421):86-88. DOI:10.2109/jcersj2.122.86 · 0.85 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A novel series of Dion-Jacobson type layered perovskite RbLaNb2−2xTixWxO7 (x=0, 0.1, and 0.2) and KCa2Nb3−2xTixWxO10 (x=0, 0.15, and 0.3) have been synthesized. The XRD patterns confirm that the optimum conditions for synthesis of RbLaNb2−2xTixWxO7 and KCa2Nb3−2xTixWxO10 are 1000 and 1100 degree for 6 h, respectively. The estimated optical band gap energies of RbLaNb2O7, RbLaNb1.8Ti0.1W0.1O7 and RbLaNb1.6Ti0.2 W0.2O7 are 3.21, 3.18 and 3.11, respectively. The influence of the partial substitution of Ti and W on the photo-catalytic activity of pure RbLaNb2O7 was evaluated by using the degradation of phenol for 4 hours. At the end of experiment, the normalized concentration of phenol is 0.9, 0.8, 0.5 by RbLaNb2O7, RbLaNb1.8Ti0.1W0.1O7 and RbLaNb1.6Ti0.2W0.2O7 respectively, which indicates that the substitution of Ti and W for Nb in RbLaNb2O7 layered perovskites could increase the photocatalytic efficiency. The photocatalytic activities of KCa2Nb3−2xTixWxO10 were also tested and the result has been shown that the phenol degradation by RbLaNb2−2xTixWxO7 is better than KCa2 Nb3−2xTixWxO10.