Zn0.8−4xHoxOy (0.05 ≤ x ≤ 0.10) diluted magnetic semiconductors were prepared by the solid state reaction method. We have studied the structural properties of the samples by using the XRD, SEM, and EDX techniques. The SEM results clearly demonstrate that Ho3+ ions are quite well substituted for Zn2+ in the ZnO lattice, and the grains of the samples are very well connected to each other and tightly packed. From the XRD and EDX spectra of the samples, it has been concluded that the substitution of Ho causes no change in the hexagonal wurtzite structure of ZnO. According to our M–H and M–T measurements paramagnetism has been observed for all the samples from our attainable lowest temperature of 10 K to 300 K. Furthermore, the trend of the AC-susceptibility (χ) versus temperature curves, measured under an AC-magnetic field of 10 Oe, also support our conclusion about the paramagnetic contribution in the Zn0.8−4xHoxOy compounds explored in this study. In order to clearly see the paramagnetic contribution, and whether there is also a ferromagnetic or antiferromagnetic contribution or not the inverse susceptibility (1/χ) against temperature curves are also plotted. Those curves indicate that, the substitution of Ho into the ZnO compound causes, in addition to the paramagnetism, a weaker antiferromagnetic (AFM) interaction. 相似文献
Ho3+/Yb3+ co‐doped PbTiO3 nanocrystals with different content of dopant were successfully prepared via a facile hydrothermal method. The purity, morphology, element distribution, chemical state and up‐conversion (UC) photoluminescence (PL) of PbTiO3 nanocrystals affected by Ho3+ dopant are investigated systematically. X‐ray diffraction (XRD) results illustrate that PbTiO3 samples with the doping Ho3+ concentration ranging from 0 to 5 mol‐% are perovskite structure. The doping Ho3+ ions have no change on the crystal structure of perovskite PbTiO3. Owing to the non‐equivalent substitution of Ho3+ to Ti4+ in PbTiO3, the particle size of Ho3+/Yb3+ co‐doped PbTiO3 samples is decreased as well as the particle agglomeration is detected. Moreover, Ho and Yb ions have uniform distributions in the PbTiO3 nanoparticles as the presence of Ho3+ and Yb3+ cations. The up‐conversion spectra demonstrate that Ho/Yb co‐doped PbTiO3 samples have up‐conversion emissions centered at 550 nm, 660 nm and 755 nm, corresponding to the transitions of 5F4(5S2)→5I8, 5F5→5I8 and 5S2(5F4)→5I7 of Ho3+ ions. Additionally, the effect of temperature on the UC PL property of Ho3+/Yb3+ co‐doped PbTiO3 system is further investigated. The sensitivity and the trend of Ho3+/Yb3+ co‐doped PbTiO3 samples in temperature from 298 k to 493K are calculated on the basis of fluorescence intensity ratio (FIR) method. Ho3+/Yb3+ co‐doped PbTiO3 nanocrystals are verified the high potential in the optical temperature sensing. 相似文献
Ferroelectric (Bi0.9RE0.1)(Fe0.975Co0.025)O3-δ (RE = Eu, Tb and Ho) thin films were prepared on Pt(111)/Ti/SiO2/Si(100) substrates via a chemical solution deposition method. All thin films were crystallized in a distorted rhombohedral perovskite structure confirmed by using an X-ray diffraction and a Raman scattering analyses. Compared to the pure BiFeO3 thin film, improved electrical and ferroelectric properties were observed for the co-doped thin films. Among the thin films, the lowest leakage current density of 4.28 × 10?5 A/cm2 was measured at an applied electric field of 100 kV/cm for the (Bi0.9Ho0.1)(Fe0.975Co0.025)O3-δ thin film. This value is approximately three orders lower than that of the pure BFO thin film. Furthermore, a large remnant polarization (2Pr) of 60.2 μC/cm2 and a low coercive field (2Ec) of 561 kV/cm at 980 kV/cm were observed from the (Bi0.9Ho0.1)(Fe0.975Co0.025)O3-δ thin film. 相似文献
Visible up-conversion emissions at (435, 545, 580, 675 and 690 nm) and (437, 547 575 and 675 nm) have been observed from the sol-gel derived nano-crystalline Ho3+: BaTiO3 powders and thin films respectively, under 808 nm laser diode excitation emissions. Combined with the energy level structure of Ho3+ ions and the kinetics of the visible emissions, the up-conversion mechanism has been analyzed and explained. The blue, green and red emissions of both samples has been attributed to the ground state-directed transition from (5F1), (5S2) and (5F5), which are populated through excited state absorption (ESA) for 808 nm excitation. Nano-structure pure barium titanate and doped with different concentrations of Ho3+ ions in the from of powder and thin film have been prepared by sol-gel technique, using barium acetate (Ba(Ac)2), and titanium butoxide (Ti(C4H9O)4), as precursors. The thin films were prepared by sol-gel spin coating method. The as-grown thin films and powders were found to be amorphous, which crystallized to the tetragonal phase after heating at 750°C in air for 30 minutes. The crystallite sizes of the thin film and powder both doped with 4% Ho3+ ions was found to be equal to 11 and 16 nm, respectvely. 相似文献
Undoped zinc oxide (ZnO) and aluminium-doped zinc oxide (ZAO) thin films have been prepared on glass substrates by RF magnetron
sputtering from ceramic and nanopowder targets at room temperature (RT). The effects of target nature on the properties of
the films have been studied. The X-ray diffraction (XRD) patterns show that ZnO and Al-doped ZnO thin films are highly textured
along the c-axis perpendicular to the surface of the substrate from either nanopowder or ceramic targets. From the SEM images,
it appears that the surface morphologies of ZAO films exhibit difference from that of undoped ZnO films. All films exhibit
a transmittance higher than 80% in the visible region. The optical band gap (Eg) of ZnO and ZAO films obtained from nanopowder target is higher than those prepared using ceramic target. In two cases, Al-doping
leads to a larger optical band gap (Eg) of the films. 相似文献
We report the effect of Mg+2 substitution (by Zn+2) on crystallization kinetics, microstructure, thermal and mechanical properties of boroaluminosilicate glass. Zn2+ was selected for Mg2+ on the basis of similar ionic radius in six coordination system (Mg2+∼0.72 Å, Zn2+∼0.75 Å). The melt-quenched glasses with SiO2–(1 − x) MgO–Al2O3–K2O–B2O3–MgF2 (BPAS)/x ZnO system, have been investigated to establish the effect of Zn+2/Mg+2 ratios. It is found that the density of BPAS glass without zinc content is 2.52 g/cm3 and increased linearly on substitution of Mg2+ by 5–32 mol% ZnO. Tg and Td of BPAS glass initially increased on adding 5 mol% ZnO and then decreased on further addition. From DSC study, it is found that the crystallization exotherm changes significantly in the temperature range 750–1000 °C, where different crystalline phases are formed, and the activation energy of crystallization (EC) varies in the range of 254–388 kJ/mol. The crystalline phases formed in opaque BPAS glass-ceramic, derived by controlled heat treatment at 800 and 1050 °C (4 h), are identified as fluorophlogopite [KMg3(AlSi3O10)F2] mica and willemite (Zn2SiO4) by XRD technique, and confirmed by FTIR spectroscopy. The change of crystallization phenomena varying Zn+2/Mg+2 ratios correspond to significant microstructural change. A wide range of thermal expansion (CTE) values are obtained for the BPAS glasses and corresponding glass-ceramics. CTE (50–500 °C) of BPAS glass without zinc content is 7.76 × 10−6/K, and decreased sequentially on increasing Zn+2/Mg+2 ratio. The density of glass-ceramics after heating at 800 and 1050 °C increased linearly with increasing Zn+2 substitution for Mg+2. Microhardness of the BPAS glasses is in the range of 4.26–6.15 GPa and found to be increased to 4.58–6.78 GPa after crystallized at 1050 °C. 相似文献
Aluminum-doped ZnO thin films with pebble-like structures have been successfully deposited on glass substrates by successive ionic layer adsorption reaction method. The effect of percentage composition of the aluminum dopant on the flower-like clusters of the ZnO nanostructures on the structure, morphology, and optical properties was investigated. The ZnO thin films which were crystallized in hexagonal wurtzite structures with crystallite sizes of 44, 51, 56, and 43 nm for the intrinsic and 1, 3, and 5% Al-doped ZnO thin films, respectively. Preferred orientation of crystallites is in all cases in [001] direction perpendicular to the sample surface The Raman spectroscopy revealed decrease in the intensity of the ZnO characteristic peak due to the substitution of the Zn2+ atoms by the Al3+ and attributed to potential fluctuations of the alloy disorder. The introduction of the Al3+ dopant significantly increased the optical band gap.
A new series of mononuclear Ho3+ complexes derived from the β-diketonate anions: 4,4,4-trifluoro-1-phenyl-1,3-butanedioneate (btfa−) and 4,4,4-trifuoro-1-(naphthalen-2-yl)-1,3-butanedionate (ntfa−) have been synthesized, [Ho(btfa)3(H2O)2] (1a), [Ho(ntfa)3(MeOH)2] (1b), (1), [Ho(btfa)3(phen)] (2), [Ho(btfa)3(bipy)] (3), [Ho(btfa)3(di-tbubipy)] (4), [Ho(ntfa)3(Me2bipy)] (5), and [Ho(ntfa)3(bipy)] (6), where phen is 1,10-phenantroline, bipy is 2,2′-bipyridyl, di-tbubipy is 4,4′-di-tert-butyl-2,2′-bipyridyl, and Me2bipy is 4,4′-dimethyl-2,2′-bipyridyl. These compounds have been characterized by elemental microanalysis and infrared spectroscopy as well as single-crystal X-ray difraction for 2–6. The central Ho3+ ions in these compounds display coordination number 8. The luminescence-emission properties of the pyridyl adducts 2–6 display a strong characteristic band in the visible region at 661 nm and a series of bands in the NIR region (excitation wavelengths (λex) of 367 nm for 2–4 and 380 nm for 5 and 6). The magnetic properties of the complexes revealed magnetically uncoupled Ho3+ compounds with no field-induced, single-molecule magnet (SMMs). 相似文献
Zinc-substituted lithium tantalate thin films were fabricated for improving the electrical resistivity by compensating the
valence of lattice defects in LiTaO3 crystal. The films with the chemical composition of (Li1.00-xZnx)TaO3 were fabricated on (111)Pt/TiO2/SiO2/(100)Si substrate by a chemical solution deposition technique using metal-organic precursors. Dense films consisting of a
ilumenite-type crystalline phase were deposited by spin coating on the substrates, followed by heat-treatment at 650°C for
5 min in air. The leakage current density of the LiTaO3 film was reduced from approximately 10−4 to 10−6 A/cm2 by substituting Zn2+ ions for Li+ ions in the LiTaO3 films. Polarization–electric field hysteresis loop was improved significantly by partial substitution of Zn2+ for Li+ ions, which is based on the enhancement of electrical resistivity. 相似文献
ZnO thin films were deposited onto glass subsrates by a Sol-gel spin coating method. The structural and optical properties
of ZnO thin films were investigated. The molar ratios of the zinc acetate dihydrate to Monoethanolamine were maintained 1:1.
The as-grown film was sintered 250 °C for 10 min, then annealed in air at 500 °C for 30 min. The XRD results indicate that
ZnO films were strongly oriented to the c-axis of the hexagonal nature. Absorption measurements were carried out as a function
of temperature with 10 K steps in the range 10–320 K. The band gap energy was measured 3.275 and 3.267 eV for 0.5 and 1.0
molarity (M) ZnO thin films at 300 K. The steepness parameters were observed between 10 and 320 K and their extrapolations
converged at (E0, α0) = 3.65 eV, 172,819 cm−1 and 3.70 eV, 653,436 cm−1 for 0.5 and 1.0 M ZnO thin films, respectively. 相似文献
Alloying materials having different band gaps is a tool to tailor the optical energy gaps of semiconducting materials. In the present study, the effect of alloying ZnO with CaO was investigated. Thin films of Zn(1−x)CaxO (0 ≤ x ≤ 0.20) were deposited on glass substrates by spray pyrolysis technique. All the films possessed nanocrystalline grains and crystallinity deteriorated with increase in Ca2+ substitution level. Elemental composition analysis confirmed the presence of Ca in the samples. Films showed good optical transmission in the visible and near infrared region and the absorption edge blue-shifted with Ca2+ substitution. Optical energy gap enhanced by 9.89% upon 20% Ca2+ substitution. Photoluminescence analysis also confirmed band gap broadening with mesovalent cation substitution. 相似文献
The effect of the dispersion of zinc oxide (ZnO) nanoparticles in the zinc ion conducting gel polymer electrolyte is studied. Changes in the morphology/structure of the gel polymer electrolyte with the introduction of ZnO particles are distinctly observed using X-ray diffraction and scanning electron microscopy. The nanocomposites offer ionic conductivity values of >10?3 S cm?1 with good thermal and electrochemical stabilities. The variation of ionic conductivity with temperature follows the Vogel–Tamman–Fulcher behavior. AC impedance spectroscopy, cyclic voltammetry, and transport number measurements have confirmed Zn2+ ion conduction in the gel nanocomposites. An electrochemical stability window from ?2.25 to 2.25 V was obtained from voltammetric studies of nanocomposite films. The cationic (i.e., Zn2+ ion) transport number (t+) has been found to be significantly enhanced up to a maximum of 0.55 for the dispersion of 10 wt.% ZnO nanoparticles, indicating substantial enhancement in Zn2+ ion conductivity. The gel polymer electrolyte nanocomposite films with enhanced Zn2+ ion conductivity are useful as separators and electrolytes in Zn rechargeable batteries and other electrochemical applications. 相似文献
The ferromagnetic and photocatalytic properties of pure ZnO, Zn0.97Gd0.01Li0.02O, Zn0.97Gd0.01Na0.02O, Zn0.97Gd0.01Mn0.02O and Zn0.97Gd0.01Fe0.02O nanoparticles prepared by sol-gel technique were investigated. The XRD, EDX, HR-TEM, FTIR and diffuse reflectance analyses confirm the formation of single phase ZnO wurtzite structure with effective incorporation of Gd/Li, Na, Mn or Fe ions into ZnO host lattice. Based on Kubelka-Munk equation, the optical band gap of pure ZnO nanoparticles was estimated to be 3.22 eV and implantation of Gd-based dual dopants induces red shifts between 0.01 and 0.29 eV. For pure ZnO nanoparticles, noticeable ferromagnetic performance was observed with saturation magnetization of 0.0133 emu/g and coercivity of 85 Oe. The binary dopants of Gd/Mn or Na induce strong enhancements in the saturation magnetization of pure ZnO nanoparticles. Where, Zn0.97Gd0.01Na0.02O and Zn0.97Gd0.01Mn0.02O samples exhibited perfect hysteresis loops with saturation magnetization of 0.34 and 0.717 emu/g, respectively. Higher photocatalytic activity, 97%, for methyl orange degradation was observed for Zn0.97Gd0.01Na0.02O nanoparticles within 210 min under UV irradiation. The particles size and agglomeration, ionic radii of dopants and recombination centers have main effects on the photocatalytic activity performance of ZnO nanoparticles. The dual dopants of Gd/Mn efficiently trigger the room temperature ferromagnetism of the pure ZnO; but Gd/Na blend revealed the best effect in methyl orange degradation (97%). 相似文献
Pure and Co-doped ZnO nanorods have been synthesized by a hydrothermal process. The structure, morphology and properties of as-prepared samples have been studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectrometer as well as by superconducting quantum interference device (SQUID). The structure and morphology analyses show that Co doping can slightly impede the ZnO crystallinity, influence the nanorods morphology, but cannot change the preferred growth orientation of ZnO nanorods. The amount of Co doping contents is about 3.0 at% in ZnO nanorods and dopant Co2+ ions substitute Zn2+ ions sites in ZnO nanocrystal without forming any secondary phase. The optical measurements show that the Co doping can effectively tune energy band structure and enrich surface states in both UV and VL regions, which lead to novel PL properties of ZnO nanorods. In addition, ferromagnetic ordering of the as-synthesized Zn1?xCoxO nanorod arrays has been observed at room temperature, which should be ascribed to sp–d and d–d carrier exchange interactions and presence of abundant defects and oxygen vacancies. 相似文献
ZnO/Co3O4 porous nanocomposites were successfully fabricated by the thermal decomposition of Prussian Blue analogue (PBA) Zn3[Co(CN)6]2 nanospheres obtained at room temperature. Interestingly, ZnO/Co3O4 porous nanocomposites exhibit room‐temperature ferromagnetism. Moreover, the ZnO/Co3O4 porous nanocomposites show good catalytic activity for CO oxidation, and the CO conversion rate reaches 100 % at 250 °C. It is suggested that the synergistic effect of each component, relative high surface area (32 m2 g?1) and porous structure lead to the promising catalytic properties. 相似文献
Ho2O[SiO4] and Ho2S[SiO4]: Two Chalcogenide Derivatives of Holmium(III) ortho‐Oxosilicate Ho2O[SiO4] crystallizes monoclinically with the space group P21/c (a = 904.15(9), b = 688.93(7), c = 667.62(7) pm, β = 106.384(8)°, Z = 4) in the A‐type structure of rare‐earth(III) oxide oxosilicates. Yellow platelet‐shaped single crystals were obtained as by‐product during an experiment to synthesize Ho3Cl[SiO4]2 by reacting Ho2O3 and SiO2 in the ratio 4 : 6 with an excess of HoCl3 as flux at 1000 °C for seven days in evacuated silica ampoules. Both crystallographically different Ho3+ cations show coordination numbers of 8+1 and 7 with coordination figures of 2+1‐fold capped trigonal prisms and octahedra, in which one of the vertices changes to an edge by two instead of one coordinating atoms, respectively. The O2— anion not linked to silicon is surrounded tetrahedrally by four Ho3+ cations which built a layer parallel (100) by vertex‐ and edge‐sharing of the [OHo4]10+ units according to {[(O5)(Ho1)1/1(Ho2)3/3]4+}. Within rhombic meshes of these layers the isolated oxosilicate tetrahedra [SiO4]4— come to lie. Ho2S[SiO4] crystallizes orthorhombically in the space group Pbcm (a = 605.87(5), b = 690.41(6), c = 1064.95(9) pm, Z = 4). It also emerged as a single‐crystalline by‐product obtained during the synthesis of Ho2OS2 by reaction of a mixture of Ho2O3, Ho and S with the wall of the evacuated silica tube used as container with an excess of CsCl as flux at 800 °C. The structure of the yellow platelet‐shaped, air and water resistant crystals also distinguishes two Ho3+ cations with bicapped trigonal prisms and trigondodecahedra as coordination polyhedra for CN = 8. The S2— anions are almost square planar surrounded by four Ho3+ cations, but situated completely outside this plane. The [SHo4]10+ squares form strongly corrugated layers perpendicular to [100] by corner‐sharing according to {[(S)(Ho1)2/2(Ho2)2/2]4+}. Contrary to the oxide oxosilicates the isolated oxosilicate tetrahedra [SiO4]4— do not lie within the rhombic meshes of these layers, but above and below the (Ho2)3+ cations while viewing along [100]. 相似文献