Advanced Materials Research Vols. 634-638

Abstract: A series of Ca_1.95P₂O₇:0.05Eu³⁺, B³⁺, M⁺ (M=Li, Na, K) phosphors were prepared by combustion synthesis method using boric acid as flux and M⁺ as charge compensator. The crystal structure and luminescent properties were investigated. The emission spectra show that the most intensive emission peak is located at 612nm, corresponding to the ⁵D₀-⁷F₂ transition of Eu³⁺. The phosphors can be efficiently excited by 394nm and 464nm light, which are matched well with the emission wavelength of near UV and blue light-emitting chips, respectively. The results show that boric acid is effective in improving the luminescence intensity, and the optimum molar ratio of boric acid to the pyrophosphate is 0.09. The relative emission intensities of Eu³⁺ (⁵D₀-⁷F₂) in Ca₂P₂O₇:Eu³⁺ phosphors with M⁺ (M=Li, Na, K) introduced as charge compensator are significantly enhanced, and the phosphor added with Na+ show the strongest emission.

Abstract: Thin films of perovskite manganite La_0.9Hf_0.1MnO₃ (LHMO) have been grown on (100) SrTiO₃ single-crystal substrates with different growth pressures by pulsed laser deposition. The different transport behaviors of films have been fitted by various models. The results clearly demonstrate that oxygen pressure is an efficient way to change the transport behaviors of LHMO films. All the transport behaviors observed in LHMO films can be better fitted by Mott’s variable range hopping model than the other two models.

Abstract: High-resolution synchrotron radiation x-ray absorption data on Mn K- and L3-edge for semimagnetic semiconductor Zn1-xMnxTe bulk materials are presented. A detailed analysis of the extended x-ray absorption fine structure by using the IFEFFIT program, and the chemical bonds of Mn-Te are obtained. The x-ray absorption near-edge structure of the Mn K- and L3-edges are investigated, and the electronic structure of Zn1-xMnxTe with various compositions are studied.

Abstract: The long afterglow luminescent materials Sr₃Al₂O₆: Eu, Sm and Sr₃Al₂O₆: Eu, Dy (denoted as S1 and S2, respectively) were synthesized via solid-state reaction. X-ray diffraction, fluorescence spectrophotometer and thermal luminescent spectroscope were employed to characterize the phosphors. The excitation spectra are all well simulated by eight Gaussian curves, indicating that they originate from the 4f⁷(⁸S_7/2)–4f⁶5d(⁸H_J) transitions of Eu²⁺. The excitation spectra intensity of S1 is much stronger than that of S2, which indicates that there is a more efficient energy transfers from Sm³⁺ to Eu²⁺. The thermally stimulated luminescence (TSL) curve can be fitted to four TSL peaks and the low-temperature TSL peak is responsible for the long lasting phosphorescence. The proposed explanation for the afterglow property is discussed.

Abstract: A novel S-doped Sr₃SiO₅: Eu²⁺ phosphor was synthesized employing high temperature solid-state reaction method under reductive atmosphere environment. The crystal structure and photoluminescence properties of the phosphor, and the effect of S^2- doping concentration on the photoluminescence intensity of Eu²⁺ was studied in details. The results show that the crystal structure of Sr₃SiO₅: Eu²⁺is not changed upon S^2- doping. When the doping concentration of S^2- is 1 wt%, the phosphor shows the maximum emission intensity, which is higher than that of Sr₃SiO₅: Eu²⁺ without S^2-. Moreover, the addition of S^2- results in an slightly shift of its emission spectra towards the red region, indicating that the S-doped Sr₃SiO₅: Eu²⁺ is an excellent yellow-orange phosphor for warm white LEDs.

Abstract: Ni-P modified hollow cenosphere was used to prepare infrared stealth coating. Infrared Spectrometer, Scanning Electron Microscope, Infrared Emissivity Testing Device are used to study the performance of the infrared stealth coating. Influencing factors of infrared emissivity of coating are analyzed comprehensively. The lowest emissivity of infrared stealth coating in 8-14um wavebands is 0.63 and the ability of controlling the coating surface temperature is raised.

Abstract: A novel perpendicular magnetic material was obtained in the annealed Co/native oxide/Pd multilayer films. Upon thermal annealing in a vacuum, a sharp transition of magnetic anisotropy from in-plane to out-of-plane is observed for the Co/native oxide/Pd multilayers with 20 Å Co layers. These annealed Co/native oxide/Pd multilayers possess extremely large effect perpendicular anisotropy field (H_eff) and perpendicular anisotropy energy (K_u), with the maximum H_eff of 17 kOe and K_u of 5.1×10⁶ erg/cm³ obtained in the annealed Co(20 Å)/native oxide/Pd(10 Å) multilayers. Moreover, the large perpendicular magnetic anisotropy sustains with annealing temperature varying from 200°C to 400°C, indicative of high thermal stability. The present results open the way to a third alternative for the realization of thermally stable perpendicular magnetic electrodes of tunnel junctions.

Abstract: Indium doped zinc oxide (ZnO:In) films were prepared in oxygen-rich condition by direct current(DC) reactive magnetron sputtering. The X-ray diffraction(XRD) pattern presented that the crystal quality of ZnO:In films was improved by the introduction of nitrogen into ambience, meanwhile the element constituent was investigated by X-Ray photoelectron spectroscopy(XPS). The photoluminescence(PL) spectra showed the visible emission was originated from two different defects. The current-voltage characteristic and persistent photoconductivity(PPC) phenomena were also explained, when the oxygen vacancies(VO) may act trap centers in persistent photoconductivity.

Abstract: The spin Hamiltonian parameters (g factors and the hyperfine structure constants) for the octahedral interstitial Fe⁰ and Mn in silicon are theoretically investigated using the perturbation formulas of these parameters for a 3d⁸ ion under octahedral environments based on the cluster approach. The theoretical results show good agreement with the experimental data, and the ligand contributions should be considered due to the strong covalency of the systems. The interstitial occupation of the above novel 3d⁸ impurities of rare valence states in silicon is discussed.

Abstract: The polymer stabilized liquid crystals (PSLC) films was prepared subsequently based on the mesogenic diacrylate monomer 4,4’-bis[6-(acryloyloxy)-hexyloxy]biphenyl (BAB6). The effects of BAB6 on the morphology of polymer network as well as the electro-optical properties of the PSLC films were investigated. The helical structure of liquid crystals was observed in the morphology of polymer network by SEM. Further, a single switching process was observed at lower monomer concentration in this study compared with the former publication. When BAB6 concentration reached 7 %, the response time and contrast ratio of PSLC film were 7 ms and 16.8, respectively.