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1.
A novel long-lasting afterglow phosphor ZrO2:Ti is prepared by the conventional solid-stated method and their luminescent properties are investigated. A bluish white strong and broad emissive band, which is attributed to originate from the recombination of electrons trapped by F+ centers and the holes created in Valence band, is observed under 254 nm UV irradiation. The identical color long afterglow, which lasts about 1 h, is found in the ZrO2:Ti phosphor after removing the 254 nm UV light. The mechanism of the long lasting phosphorescence (LLP) has been discussed based on the thermoluminescence (TL) results. The replacement of Zr by Ti produces more anion vacancies, resulting in the enhanced photoluminescence (PL) and LLP of ZrO2:Ti sample. These results indicate that ZrO2:Ti phosphor has potential promising applications. 相似文献
2.
采用共沉淀法制备了纳米晶ZrO2-Al2O3∶Er3+发光粉体.所制备的粉体室温下具有Er3+离子特征荧光发射,主发射在绿光,其中位于547 nm、560 nm的绿光最强,并得出稀土离子与基质之间有能量传递.对不同煅烧温度下的样品研究表明:因不同温度下所制得的样品晶相不同.研究了纳米晶ZrO2-Al2O3∶Er3+及ZrO2-Al2O3∶Er3+/Yb3+的上转换发光,并分析了上转换的跃迁机制.发现ZrO2-Al2O3∶Er3+的绿光为双光子过程,而ZrO2-Al2O3∶Er3+、Yb3+的上转换光谱中,红光和绿光也为双光子过程,而极弱的蓝光为三光子过程.讨论了Er3+的浓度猝灭现象.最适宜掺杂浓度的原子分数为2%(Er3+/Zr4+). 相似文献
3.
B.P. Chandra 《Journal of luminescence》2010,130(11):2218-2222
ZrO2:Ti phosphors show such a strong mechanoluminescence (ML) that it can be seen in day light with naked eye. When a pellet of ZrO2:Ti phosphor mixed in epoxy resin is deformed in the elastic region at a fixed strain rate using a testing machine, ML intensity increases linearly with time, and when the deformation is stopped, ML intensity decreases exponentially with time. For a given strain rate, ML intensity increases linearly with pressure, and for a given pressure, ML intensity increases linearly with the strain rate. The total ML intensity, in the deformation region, increases quadratically with pressure; however, the total ML intensity in the post-deformation region increases linearly with pressure. ML intensity decreases with successive number of pressings, whereby the reduced ML intensity can be recovered by UV-irradiation of the sample. ML intensity increases linearly with density of filled electron traps and it is optimum for a particular concentration of Ti in ZrO2. ML intensity should change with increasing temperature of the phosphors. Although ZrO2 is non-piezoelectric as a whole, it seems that the local structures near the Ti ions in ZrO2 crystals are in the piezoelectric phase. The elastico ML in ZrO2 phosphors can be understood on the basis of the localized piezoelectrification-induced detrapping model. According to this model, the localized piezoelectric field near Ti ions causes detrapping of electrons and subsequently the detrapped electrons moving in the conduction band are captured by the energy state of excited Ti4+ ions, whereby excited Ti4+ ions are produced and consequently the decay of excited Ti4+ ions gives rise to the light emission. The expressions derived on the basis of this model are able to explain satisfactorily the characteristics of ML. The relaxation time of localized piezoelectric charges and the threshold pressure for the ML emission can be determined from ML measurements. The long decay of elastico ML indicates the possibility of exploring persistent elastico ML, which may be useful for the fabrication of dim light sources capable of operating without any external power. 相似文献
4.
Implication of the role of oxygen anions and oxygen vacancies for methanol decomposition over zirconia supported copper catalysts 总被引:1,自引:0,他引:1
The interaction of methanol with Cu, monoclinic ZrO2, and Cu/m-ZrO2 catalysts has been investigated by temperature programmed desorption (TPD) and reaction (TPRS) with the aim of understanding the nature of the surface sites and the mechanism involved in methanol decomposition. A synergetic effect has been detected since the combination of copper and ZrO2 significantly facilitates the methanol decomposition with the facile evolution of H2 and CO species at much lower desorption temperature. In conjunction with DRIFTS and H2-TPD measurements of the Cu/ZrO2 sample reduced at elevated temperatures, methanol decomposition over Cu/ZrO2 is suggested to occur primarily on ZrO2 with the aid of the presence of oxygen anions and oxygen vacancies generated by species-spillover between copper and zirconia. The interface between copper and zirconia is also evidenced to be crucial to the decomposition of methanol, with the main role of metallic Cu being to provide sites for H2 removal by efficiently recombining the hydrogen atoms formed during the dehydrogenation of species located on zirconia. 相似文献
5.
The electrical conductivity of ZrO2 doped with Co3O4 has been measured at various temperatures for different molar ratios. The conductivity increases due to the migration of vacancies created by doping. The conductivity is also found to increase with rise in temperature up to 120°C, and after attaining a maximum the conductivity decreases due to a collapse of the lattice framework. A second rise in conductivity around 460°C in all the compositions confirms the phase transition in ZrO2 from monoclinic to tetragonal symmetry. X-ray powder diffraction and DTA studies were carried out for confirming the doping effects and the transition in ZrO2. 相似文献
6.
We present in this paper the experimental results of photoluminescence spectra of Ba0.5Sr0.5TiO3 ceramics. An emission band centered at about 920 nm has been observed at room temperature. When we change the amount of oxygen vacancies in these samples by thermal treatment, these samples show an enhancement of luminescence. Our experimental results indicate that the origin of the photoluminescence is related to the oxygen vacancies in these samples. 相似文献
7.
Two-layer ZrO2/SiO2 and SiO2/ZrO2 films were deposited on K9 glass substrates by sol–gel dip coating method. X-ray photoelectron spectroscopy (XPS) technique was used to investigate the diffusion of ZrO2/SiO2 and SiO2/ZrO2 films. To explain the difference of diffusion between ZrO2/SiO2 and SiO2/ZrO2 films, porous ratio and surface morphology of monolayer SiO2 and ZrO2 films were analyzed by using ellipsometry and atomic force microscopy (AFM). We found that for the ZrO2/SiO2 films there was a diffusion layer with a certain thickness and the atomic concentrations of Si and Zr changed rapidly; for the SiO2/ZrO2 films, the atomic concentrations of Si and Zr changed relatively slowly, and the ZrO2 layer had diffused through the entire SiO2 layer. The difference of diffusion between ZrO2/SiO2 and SiO2/ZrO2 films was influenced by the microstructure of SiO2 and ZrO2. 相似文献
8.
Nguyen Hoa Hong Chul-Kwon Park A.T. Raghavender Antoine Ruyter Ekaterina Chikoidze Yves Dumont 《Journal of magnetism and magnetic materials》2012
Theory has predicted that high temperature ferromagnetism (FM) should be found in cubic fake-diamonds, Mn-doped ZrO2. Experimentally, it is shown that Mn-doped ZrO2 ceramics are not ferromagnetic, but the nanosized Mn-doped ZrO2 thin films grown on LaAlO3 substrates can be ferromagnets with TC above 400 K. The largest saturated magnetic moment (Ms) is huge as of about 230 emu/cm3 for the Mn0.05Zr0.95O2 films, and it decreases as the Mn content increases. The intrinsic FM is strongly associated with the cubic structure of Mn-doped ZrO2, and the Mn–Mn interactions via oxygen intermediates are important. No electrical conductivity is observed. Mn-doped ZrO2 thin films can be truly considered as excellent candidates for spintronic applications. 相似文献
9.
Effect of phase transformation on optical and dielectric properties of zirconium oxide nanoparticles
Rajababu Chintaparty Bhavani Palagiri Venkata subbha Reddy Imma Reddy 《Phase Transitions》2015,88(9):929-938
Zirconium oxide nanoparticle (ZrO2) is synthesized by the hydrothermal method at different calcination temperatures. The structural analysis is carried out by X-ray diffraction and Raman spectra. The sample prepared at 400 °C and 1100 °C showed the cubic and monoclinic phase, respectively, and the sample calcined at 600 °C and 800 °C showed the mixed phase with co-existence of cubic and monoclinic phases. Furthermore, the morphology and particle size of these samples were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis. The band gap estimated from UV–Vis spectra of ZrO2 (zirconia) nanocrystalline materials calcined at different temperatures from 400 °C to 1100 °C was in the range of 2.6–4.2 eV. The frequency dependence of dielectric constant and dielectric loss was investigated at room temperature. The low frequency region of dielectric constant is attributed to space charge effects. 相似文献
10.
Hiroyuki Takano Koichi IzumiyaNaokazu Kumagai Koji Hashimoto 《Applied Surface Science》2011,257(19):8171-8176
The active catalysts for methane formation from the gas mixture of CO2 + 4H2 with almost 100% methane selectivity were prepared by reduction of the oxide mixture of NiO and ZrO2 prepared by calcination of aqueous ZrO2 sol with Sm(NO3)3 and Ni(NO3)2. The 50 at%Ni-50 at%(Zr-Sm oxide) catalyst consisting of 50 at%Ni-50 at%(Zr + Sm) with Zr/Sm = 5 calcined at 650 or 800 °C showed the highest activity for methanation. The active catalysts were Ni supported on tetragonal ZrO2, and the activity for methanation increased by an increase in inclusion of Sm3+ ions substituting Zr4+ ions in the tetragonal ZrO2 lattice as a result of an increase in calcination temperature. However, the increase in calcination temperature decreased BET surface area, metal dispersion and hydrogen uptake due to grain growth. Thus, the optimum calcination temperature existed. 相似文献
11.
Metal-insulator-metal (MIM) capacitors were fabricated using ZrO2 films and the effects of structural and native defects of the ZrO2 films on the electrical and dielectric properties were investigated. For preparing ZrO2 films, Zr films were deposited on Pt/Si substrates by ion beam deposition (IBD) system with/without substrate bias voltages and oxidized at 200 °C for 60 min under 0.1 MPa O2 atmosphere with/without UV light irradiation (λ = 193 nm, Deep UV lamp). The ZrO2(∼12 nm) films on Pt(∼100 nm)/Si were characterized by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM), capacitance-voltage (C-V) and current-voltage (I-V) measurements were carried out on MIM structures. ZrO2 films, fabricated by oxidizing the Zr film deposited with substrate bias voltage under UV light irradiation, show the highest capacitance (784 pF) and the lowest leakage current density. The active oxygen species formed by UV irradiation are considered to play an important role in the reduction of the leakage current density, because they can reduce the density of oxygen vacancies. 相似文献
12.
Sol-gel (ZrO2/SiO2)12 ZrO2 films were prepared by spin coating method. The reflectivity spectrum of the films was measured with a Lambda 900 spectrometer. In order to investigate laser-induced damage threshold (LIDT) characteristic of highly reflective films, one-layer ZrO2 and SiO2 films, two-layer ZrO2/SiO2 and SiO2/ZrO2 films were also prepared by spin coating method. LIDT of each film was measured. Damage morphology after laser irradiation was characterized by optical microscopy (Nikon E600K). The experimental results showed that the reflectivity of (ZrO2/SiO2)12 ZrO2 film at 1064 nm and 355 nm wavelength is 99.7%. The LIDT results decreases as the number of layer of films increases. All the films have similar damage morphology. The experimental results are explained by the different temperature profiles of the films. 相似文献
13.
High aspect-ratio Li2ZrO3 nanotubes were prepared by hydrothermal method using ZrO2 nanotubes layers as templates. Characterizations of SEM, XRD, TEM and CO2 adsorption were performed. The results showed that tetragonal Li2ZrO3 nanotubes arrays containing a little monoclinic ZrO2 can be obtained using this simple method. The mean diameter of the nanotubes is approximately 150 nm and the corresponding specific surface area is 57.9 m2 g−1. Moreover, the obtained Li2ZrO3 nanotubes were thermally analyzed under a CO2 flow to evaluate their CO2 capture property. It was found that the as-prepared Li2ZrO3 nanotubes arrays would be an effective acceptor for CO2 at high temperature. 相似文献
14.
Composite photocatalysts composed of TiO2 and ZrO2 have been prepared via the sol-gel method. The as-prepared nanocomposites are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis spectrometry and fluorescence emission spectra. The results shows that TiO2/ZrO2 nanocomposites are composed of mainly anatase titania and tetragonal ZrO2. Incorporating TiO2 particles with ZrO2 plays an important role in promoting the formation of nanoparticles with an anatase structure and leads to decreased fluorescence emission intensity. Most of the TiO2/ZrO2 nanocomposites exhibited comparable photocatalytic activity compared with commercial TiO2 for the degradation aqueous methyl orange (MO) under ultraviolet irradiation, while the composite with Zr/Ti mass ratio of 15.2% shows the highest photocatalytic performances. Furthermore, the as-prepared nanocomposites can be reused with little photocatalytic activity loss. Without any further treatment besides rinsing, the photocatalytic activity of TiO2/ZrO2 (15.2%) composites is still higher than after five-cycle utilization. 相似文献
15.
Uniformly distributed polycrystalline indium nanohillocks are synthesized on silicon substrates with Au catalyst by using the radio frequency magnetic sputtering technique. The results show that the Au catalyst plays a key role in the formation of indium nanohillocks. After thermally oxidizing the indium nanohillocks at 500 ℃ in air for 5 h, the indium nanohillocks totally transform into In2O3 nanohillocks. The energy-dispersive X-ray spectroscopy result indicates that many oxygen vacancies and oxygen-indium vacancy pairs exist in the In2O3 nanohillocks. Photoluminescence spectra under an Ne laser excitation at 280 nm show broad emissions at 420 nm and 470 nm with a shoulder at 450 nm related to oxygen vacancies and oxygen-indium vacancies at room temperature. 相似文献
16.
Haowei Peng 《Physics letters. A》2008,372(9):1527-1530
Native point defects in the rutile TiO2 are studied via first-principles pseudopotential calculations. Except for the two antisite defects, all the native point defects have low formation energies. Under the Ti-rich growth condition, high concentrations of titanium interstitials and oxygen vacancies would form spontaneously in p-type samples; whereas high concentrations of titanium vacancies would form spontaneously in n-type samples regardless of the oxygen partial pressure. 相似文献
17.
通过固相反应法制备了Er3+/Yb3+共掺杂ZrO2-Al2O3粉末的样品,并对样品在980nm激光激发下的上转换发光特性进行了研究.从发射光谱可以发现,在可见光范围内有3个强的发光带,一个位于654nm附近的红光带和两个分别位于545nm、525nm附近的绿光带,分别对应于Er3+离子的以下辐射跃迁:4F9/2→4I15/2、4S3/2→4I15/2、 2H11/2→4I15/2.其中又以Er3+离子的4F9/2→4I15/2跃迁产生的红色荧光辐射最强.对其上转换发光机制进行了分析,发现这三个发光过程都是双光子过程.对样品粉末进行了XRD检测,发现ZrO2主要以立方相为主,并且计算得到了这种立方结构的晶格常数.Al2O3固溶于ZrO2中,Al3+嵌入ZrO2后产生氧空位,导致ZrO2晶体的对称性降低,这种结构变化更有利于提高上转换效率,即上转换发光强度增强.
关键词:
3+/Yb3+')" href="#">Er3+/Yb3+
上转换
2-Al2O3')" href="#">ZrO2-Al2O3
荧光
稀土 相似文献
18.
Role of the MOCVD deposition conditions on physico-chemical properties of tetragonal ZrO2 thin films
K. Galicka-Fau C. Legros M. Andrieux M. Brunet J. Szade G. Garry 《Applied Surface Science》2009,255(22):8986-8994
High-k ZrO2 thin films suitable for microelectronics applications were deposited by DLI-MOCVD method on planar Si (1 0 0) and pores etched in Si (1 0 0). The effects of various experimental parameters such as temperature of substrates, injection frequency, concentration of the precursor and oxygen partial pressure in the reactive chamber, were investigated in order to produce a single tetragonal ZrO2 phase which exhibits, according to the literature, the best permittivity.Taking into account the crystal structure, microstructure and chemistry of the films, the expected phase was successfully deposited for high temperature of substrates, relatively high feeding rate and low oxygen partial pressure. Although the 3D coverage is actually not perfect in high aspect ratio pores, the electric properties of this sample are very promising with permittivity up to 27. 相似文献
19.
The Sn-TiO2−X nanoparticles have been prepared via a rapid and simple stannous chemical reducing method. The as-prepared Sn-TiO2−X nanoparticles were investigated by means of surface photovoltage spectroscopy (SPS), XPS, and DRS technology as well as photocatalytic degradation of RhB were studied under illumination. The experiment results revealed that the reduction of the TiO2 particles raised their Fermi level, which can enhance the driven force of photoinduced electrons transferring from TiO2 to adsorbed O2 and SnO2 on the surface of TiO2. On the other hand, the amount of oxygen vacancies of the Sn-TiO2−X increased after the stannous chemical reduction. The oxygen vacancies can also effectively inhibit the recombination of photoinduced electrons and holes pairs. These factors are favorable to the photocatalytic reaction. 相似文献
20.
The resistive switching properties in amorphous Pr0.67Sr0.33MnO3 films deposited by pulsed laser deposition are investigated.Reproducible and bipolar counter-8-shape and 8-shape switching behaviours of Au/Pr0.67Sr0.33MnO3 /F:SnO2 junctions are obtained at room temperature.Dramatically,the coexistence of two switching polarities could be reversibly adjusted by an applied voltage range.The results allocated those two switching types to areas of different defect densities beneath the same electrode.The migration of oxygen vacancies and the trapping effect of electrons under an applied electric field play an important role.An interface-effect-related resistance switching is proposed in an amorphous Pr0.67Sr0.33MnO3-based memory cell. 相似文献