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The effects of surface conditions on photo-induced-carrier (PIC) diffusion are studied by solving one-dimensional continuity equation. Using various forms of ZnO samples with different surface conditions, the PICs lost at sample surface are substantiated to have important contributions to the visible luminescence. For unpassivated ZnO nanorods and single-crystal samples that undergo a high-temperature annealing in air, the visible luminescence originating from the PICs diffused to the surface is estimated more than 99.8 % and 70 % at room temperature, respectively, and more than 99.99 % and 97 % at low temperature. The structureless luminescence caused by PICs, such as the green, yellow, and orange luminescence bands are well fitted under the framework of tail-state luminescence, while the structured green band is suggested to be in association with a specific type of surface states formed during high-temperature annealing in oxidizing atmosphere and can be fitted with Huang-Rhys model by taking into account tail-state luminescence. [ABSTRACT FROM AUTHOR]

Abstract: La2NiO4 compounds were prepared by a modified sol–gel auto-combustion method, which is a low-temperature combustion synthesis procedure using microwave-assisted sol–gel as precursors. The high-temperature transport properties of the samples were investigated. The band structure, total density of states (DOS), and partial density of states (PDOS) of low-temperature orthorhombic (Bmab) phase and high-temperature tetragonal (I4/mmm) phase for La2NiO4 were calculated in order to study the transport properties of the as-obtained samples. [Copyright &y& Elsevier]

Abstract: Ca3−x Er x Co4O9+δ (x=0, 0.05, 0.15, 0.3 and 0.5) samples were prepared using a sol–gel method followed by hot-pressing sintering technique. Powder X-ray diffraction analysis showed the single-phases of Ca3−x Er x Co4O9+δ were obtained up to x=0.3 and the crystallinity of the samples decreased with increasing Er-doping amount. The high-temperature (323–1073K) thermoelectric properties of the samples were investigated. The substitution of Er3+ for Ca2+ resulted in the decrease of electrical conductivity, thermal conductivity and the increase of Seebeck coefficient for all the samples except the x=0.05 one. The dimensionless figure of merit ZT reached 0.28 at 1073K for Ca2.7Er0.3Co4O9+δ , indicating the thermoelectric properties of CaCo4O9+δ can be enhanced by doping Er in the system. [ABSTRACT FROM AUTHOR]

Abstract: New compounds with layered structure Ca2− x Na x Co2O5 (x=0.00–0.45) were prepared by citrate sol–gel method. X-ray powder diffraction patterns of the specimens could be indexed by two monoclinic lattices with C2 space group. The Co 2p X-ray photoelectron spectroscopy (XPS) was used to study Co chemical valence. The electrical conductivity and the thermoelectric power for the specimens were measured between 350 and 950K. Both properties increased with rising temperature in the temperature range measured. The substitution of univalent Na+ for divalent Ca2+ had a remarkable effect on the enhancement of both properties. For Ca1.55Na0.45Co2O5 specimen, the electrical conductivity and the thermoelectric power reached 68.9Scm−1 and 165μVK−1 at 950K, respectively. Their intriguing thermoelectric properties make them candidates for thermoelectric materials. [Copyright &y& Elsevier]

LaBaCo 2 O 6−δ (LBCO) films were grown on MgO substrates by a pulsed laser deposition method in O 2 atmosphere of 2 × 10−4 and 2 Pa. The LBCO films are epitaxial, but actually consist of 90°-oriented ordered LaBaCo 2 O 6 grains in O-annealed samples. Paramagnetic to ferromagnetic transition occurs at ~200 K and the coercive fields at 10 K are as high as 8.8 and 7.2 kOe for the O-annealed low- and high-oxygen LBCO films, respectively. The high coercive fields are attributed to the co-existed 90°-oriented grains, which play a role in locking magnetic spins. A magnetization model of ferromagnetic nanoclusters is established and applied to the discussion of irreversibility in temperature-dependent magnetization curves and the fitting of magnetization loops at different temperatures, revealing that oxygen vacancies may have impacts on the magnetization of LBCO films. In addition, the electric transport properties were studied and linked to the growth behavior of LBCO films. [ABSTRACT FROM AUTHOR]

Deposition atmosphere was found to have significant impacts on the growth of single-crystal LaBaCo 2 O 6−δ (LBCO) films. In 2 × 10−4 Pa, the LBCO film grew basically along the c -axis of LaBaCo 2 O 5.5 and high-quality single-crystal LBCO film was obtained after O 2 annealing. In 2 Pa of O 2 , the dominant domains in the LBCO film became a - and/or b -axis oriented and a phase separation appeared in the O-annealed film. The O-annealed LBCO films exhibited an obvious paramagnetic to ferromagnetic transition at ~200 K and ~1.3 μ B /Co of saturated magnetic moment was obtained at 10 K. Ferromagnetic and spin-glass-like states may coexist in the LBCO films, making a deviation of the zero-field-cooled from the field-cooled magnetization at temperatures below an irreversible temperature. The LBCO films exhibited the magnetic properties close to that of nanoscale-ordered LaBaCo 2 O 6 , but the electric transport behaviors are close to that of ordered LaBaCo 2 O 6. • Deposition atmosphere having significant impacts on the growth of LBCO films. • LBCO films being close to the nanoscale-ordered LaBaCo2O6 in the magnetism. • LBCO films being close to the ordered LaBaCo2O6 in the electric transport. • FM and SG coexistence making a deviation of ZFC from FC magnetization. • Strong electron correlations being responsible for the magnetoelectronic separation. [ABSTRACT FROM AUTHOR]