共查询到20条相似文献,搜索用时 265 毫秒
1.
Haiqian Wang Weijie JiLei Zhang Yunhui GongBin Xie Yousong JiangYizhou Song 《Solid State Ionics》2011,192(1):413-418
YSZ films for anode-supported SOFCs were prepared by reactive sputtering method. It was found that the surface morphology of anode substrate has a very important effect on the quality of sputtered films. By applying an anode functional layer and making the anode surface smooth, dense and uniform YSZ films of 10 µm in thickness were successfully fabricated. The sintering behaviors of the sputtered YSZ films were also discussed. It is suggested that the optimized densification condition for the deposited YSZ films is sintering at 1250 °C for 4 h. Single cells with sputtered YSZ film as electrolyte and LSM-YSZ as active cathode materials were tested. 1.08 V open circuit voltage and a 700 mW/cm2 maximum power density were achieved at 750 °C by using humidified H2 as fuel and air as oxidant. 相似文献
2.
Two-sample (Allan) variance with a modified algorithm was applied to the determination of the experimental linewidth of a thermoelectrically-cooled continuous-wave distributed feedback quantum cascade laser at a wavelength of 4.333 μm. From successive laser transmittance scans over the CO2 ν3, (0111 − 0110) P(33) absorption line at 2307.653 cm− 1, two-sample variances were calculated for the laser frequency difference between different points on the sides of the absorption peak. From the minimum two-sample variance of the laser frequency difference between two adjacent points (5 μs between the points) on the same side of the absorption line the experimental laser linewidth was estimated to be less than 36(7) kHz at a laser power of ~ 25 mW, a laser current of 976 mA and a laser temperature of + 19.5 °C. 相似文献
3.
Lei Shi Shanghong Zhao Wen Meng Yunxia Li ShengBao Zhan Ruiping Zhu 《Optics Communications》2006,257(2):270-276
In this paper, extensive experimental results on broad-band double cladding Er3+-Yb3+ co-doped superfluorescent fiber sources (SFSs), characterizing their output power, mean wavelength, and bandwidth (BW) stability with variations of pump power, pump wavelength, and fiber temperature, have been reported. For a 55-cm fiber, SFS power from 3.7755 (maximum BW condition of more than 80 nm) to 9.1837 mW (maximum power condition, BW is about 34 nm) has been achieved. The SFS mean wavelength dependence on pump wavelength is highly pump temperature sensitive, and can be reduced to zero in a chosen pump temperature field. The intrinsic variation of the SFS mean wavelength λm with fiber temperature is also measured, and a linear variation from 15 to 45 °C with a slop of −0.053 nm/°C for Lf = 100 cm and −0.04 nm/°C for Lf = 55 cm is found. 相似文献
4.
Mixed manganese-zinc and nickel-zinc ferrites of composition Mn0.2Ni0.8−xZnxFe2O4 where x=0.4, 0.5 and 0.6 have been synthesized by the citrate precursor technique. Decomposition of the precursor at temperatures as low as 500 °C gives the ferrite powder. The ferrites have been investigated for their electrical and magnetic properties such as saturation magnetization, initial permeability, Curie temperature, AC-resistivity and dielectric constant as a function of sintering temperature and zinc content. Structural properties such as lattice parameter, grain size and density are also studied. The mixed compositions exhibited higher saturation magnetizations at sintering temperatures as low as 1200 °C. While the Curie temperature decreased with zinc content, the permeability was found to increase. The AC-resistivity ranged from 105–107 Ω cm and decreased with zinc content and sintering temperature. The dielectric constants were lower than those normally reported for the Mn–Zn ferrites. Samples sintered at 1400 °C densified to about 94% of the theoretical density and the grain size was of the order of about 1.5 μm for the samples sintered at 1200 °C and increased subsequently with sintering temperature. 相似文献
5.
T.K. PietrzakJ.E. Garbarczyk M. WasiucionekI. Gorzkowska J.L. NowinskiS. Gierlotka 《Solid State Ionics》2011,192(1):210-214
An electronically conducting nanomaterial was synthesized by nanocrystallization of a 90V2O5·10P2O5 glass and its electrical properties were studied in an extended temperature range from − 170 to + 400 °C. The conductivity of the prepared nanomaterial reaches 2 ? 10− 1 S cm− 1 at 400 °C and 2 ? 10− 3 S cm− 1 at room temperature. It is higher than that of the original glass by a factor of 25 at room temperature and more than 100 below − 80 °C. A key role in the conductivity enhancement was ascribed to the material's microstructure, and in particular to the presence of the large number of small (ca. 20 nm) grains of crystalline V2O5. The observed conductivity dependencies are discussed in terms of the Mott's theory of the electronic hopping transport in disordered systems. Since V2O5 is known for its ability to intercalate lithium, the presented results might be helpful in the development of cathode materials for Li-ion batteries. 相似文献
6.
Ce0.8Gd0.05Y0.15O1.9 (GYDC) electrolyte was prepared by a carbonate co-precipitation method. Lithium nitrate at 1, 1.5, 2 and 3 mol% was added to GYDC as sintering additive. 96% relative density was achieved for GYDC at sintering temperature of 800 °C with addition of 1.5 mol% LiNO3. The conductivities of GYDC with sintering aids LiNO3 were measured by a.c. impedance spectroscopy and showed comparable values to that of pure GYDC sample sintered at 1400 °C. A single cell with 1.5 mol% LiNO3 infiltrated GYDC electrolyte was fabricated by sintering at 800 °C for only 2 h. Lithiated NiO was synthesized by the glycine-nitrate combustion method and employed as cathode material. The cell was tested at temperatures from 500 to 575 °C and a maximum power density of 73 mW cm− 2 was obtained at 575 °C. These preliminary results indicate that LiNO3 is a very effective sintering additive for intermediate temperature solid oxide fuel cell fabrication. 相似文献
7.
D.E. Wesolowski Y.R. Patta M.J. Cima 《Physica C: Superconductivity and its Applications》2009,469(13):766-773
The densification behavior during conversion of YBa2Cu3O7−x (YBCO) films formed by the trifluoroacetate (TFA)-based metal–organic deposition (MOD) technique was compared to a non-fluorine oxycarbonate-based MOD process and nitrate-based polymer-assisted deposition (PAD). The critical current densities obtained in all processes exceeded 106 A/cm2 in films at least 300 nm thick. Rapid densification of films was observed in all processes, beginning at 700 °C in the TFA and PAD processes and 650 °C in the oxycarbonate process. YBCO nucleation occurred shortly after densification began in all processes. Residual carbon measurements were performed using wavelength dispersive spectroscopy (WDS). Carbon persisted in films from all processes until after densification began, but it was reduced to background levels soon after YBCO nucleation. Film density and second phase morphology were controlled through adjustments to the ambient oxygen partial pressure. Morphological evidence of extensive transient liquid phase formation was observed in PAD films and is consistent with the densification and nucleation behavior. The common behavior between the PAD, oxycarbonate–MOD, and TFA–MOD processes suggests that a melt forms in all systems, but the extent of this melt varies. 相似文献
8.
M. Deepa 《Applied Surface Science》2005,252(5):1568-1580
A significant influence of microstructure on the electrochromic and electrochemical performance characteristics of tungsten oxide (WO3) films potentiostatically electrodeposited from a peroxopolytungstic acid (PPTA) sol has been evaluated as a function of annealing temperature. Powerful probes like X-ray diffractometry (XRD), transmission electron microscopy (TEM), UV-vis spectrophotometry, multiple step chronoamperometry and cyclic voltammetry have been employed for the thin film characterization. The as-deposited and the film annealed at 60 °C are composed of nanosized grains with a dominant amorphous phase, as well as open structure which ensues from a nanoporous matrix. This ensures a greater number of electroactive sites and a higher reaction area thereby manifesting in electrochromic responses superior to that of the films annealed at higher temperatures. The films annealed at temperatures ≥250 °C are characterized by a prominent triclinic crystalline structure and a hexagonal phase co-exists at temperatures ≥400 °C. The deleterious effect on the electrochromic properties of the film with annealing is ascribed to the loss of porosity, densification and the increasing crystallinity and grain size. Amongst all films under investigation, the film annealed at 60 °C exhibits a high transmission modulation (ΔT ∼ 68%) and coloration efficiency (η ∼ 77.6 cm2 C−1) at λ = 632.8 nm, charge storage capacity (Qins ∼ 21 mC cm−2), diffusion coefficient (6.08 × 10−10 cm2 s−1), fast color-bleach kinetics (tc ∼ 275 s and tb ∼ 12.5 s) and good electrochemical activity, as well as reversibility for the lithium insertion-extraction process upon cycling. The remarkable potential, which the film annealed at 60 °C has, for practical “smart window” applications has been demonstrated. 相似文献
9.
The annealing temperature dependence of contact resistance and layer stability of ZrB2/Ti/Au and Ni/Au/ZrB2/Ti/Au Ohmic contacts on p-GaN is reported. The as-deposited contacts are rectifying and transition to Ohmic behavior for annealing at ≥750 °C, a significant improvement in thermal stability compared to the conventional Ni/Au Ohmic contact on p-GaN, which is stable only to <600 °C. A minimum specific contact resistance of ∼2 × 10−3 Ω cm−2 was obtained for the ZrB2/Ti/Au after annealing at 800 °C while for Ni/Au/ZrB2/Ti/Au the minimum value was 10−4 Ω cm−2 at 900 °C. Auger Electron Spectroscopy profiling showed significant Ti, Ni and Zr out diffusion at 750 °C in the Ni/Au/ZrB2/Ti/Au while the Ti and Zr intermix at 900 °C in the ZrB2/Ti/Au. These boride-based contacts show promise for contacts to p-GaN in high temperature applications. 相似文献
10.
J.H SongY.H Jeong 《Solid State Communications》2003,125(10):563-566
SrTiO3 homoepitaxy was investigated under various conditions using the pulsed laser deposition method. The growth mode was determined by in-situ reflection high-energy electron diffraction, and the surface of the films was characterized by ex-situ atomic force microscopy. At the laser fluence of 0.68 J/cm2, island growth was observed below 500 °C substrate temperature, while the growth mode turned into layer-by-layer growth above 500 °C. On further raising the substrate temperature, the step-flow growth mode prevailed above 800 °C. We thus demonstrated that step-flow growth in SrTiO3 homoepitaxy is possible at a temperature as low as 800 °C. 相似文献
11.
Aifen Tian Wei Ren Lingyan WangPeng Shi Xiaofeng ChenXiaoqing Wu Xi Yao 《Applied Surface Science》2012,258(7):2674-2678
Lead-free ferroelectric K0.5Na0.5NbO3 (KNN) thin films have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed laser deposition process. The structures, crystal orientations and electrical properties of thin films have been investigated as a function of deposition temperature from 680 °C to 760 °C. It is found that the deposition temperature plays an important role in the structures, crystal orientations and electrical properties of thin films. The crystallization of thin films improves with increasing deposition temperature. The thin film deposited at 760 °C exhibits strong (0 0 1) preferential orientation, large dielectric constant of 930 and the remnant polarization of 8.54 μC/cm2. 相似文献
12.
Structural, optical and electrical properties of CuIn5S8 thin films grown by thermal evaporation have been studied relating the effects of substrate heating conditions of these properties. The CuIn5S8 thin films were carried out at substrate temperatures in the temperature range 100-300 °C. The effects of heated substrate on their physico-chemical properties were investigated using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), optical transmission and hot probe method. X-ray diffraction revealed that the films are strong preferred orientation along the (3 1 1) plane upon substrate temperature 200 °C and amorphous for the substrate temperatures below 200 °C. No secondary phases are observed for all the films. The composition is greatly affected by heated substrate. From the optical transmission and reflection, an important absorption coefficient exceeds 105 cm−1 at 800 nm was found. As increasing the substrate temperature, the optical energy band gap decreases from 1.70 eV for the unheated films to 1.25 eV for the deposited films at 300 °C. It was found that CuIn5S8 thin film is an n-type semiconductor at 250° C. 相似文献
13.
Ohmic contact formation on n-GaN using a novel Ti/Al/W2B/Ti/Au metallization scheme was studied using contact resistance, scanning electron microscopy and Auger electron spectroscopy measurements. A minimum specific contact resistivity of 7 × 10−6 Ω cm2 was achieved at an annealing temperature of 800 °C. The contact resistance was essentially independent of measurement temperature, indicating that field emission plays a dominant role in the current transport .The Ti began to outdiffuse to the surface at temperatures of ∼500 °C, while at 800 °C the Al also began to intermix within the contact. By 1000 °C, the contact showed a reacted appearance and AES showed almost complete intermixing of the metallization. The contact resistance showed excellent stability for extended periods at 200 °C, which simulates the type of device operating temperature that might be expected for operation of GaN-based power electronic devices. 相似文献
14.
Jau-Jiun Chen Soohwan Jang F. Ren S. Rawal Hyun-Sik Kim S.J. Pearton A. Osinsky 《Applied Surface Science》2006,253(2):746-752
The specific contact resistivity and chemical intermixing of Ti/Au and Ti/Al/Pt/Au Ohmic contacts on n-type Zn0.05Cd0.95O layers grown on ZnO buffer layers on GaN/sapphire templates is reported as a function of annealing temperature in the range 200-600 °C. A minimum contact resistivity of 2.3 × 10−4 Ω cm2 was obtained at 500 °C for Ti/Al/Pt/Au and 1.6 × 10−4 Ω cm2 was obtained at 450 °C for Ti/Al. These values also correspond to the minima in transfer resistance for the contacts. The Ti/Al/Pt/Au contacts show far smoother morphologies after annealing even at 600 °C, whereas the Ti/Au contacts show a reacted appearance after 350 °C anneals. In the former case, Pt and Al outdiffusion is significant at 450 °C, whereas in the latter case the onset of Ti and Zn outdiffusion is evident at the same temperature. The improvement in contact resistance with annealing is suggested to occur through formation of TiOx phases that induce oxygen vacancies in the ZnCdO. 相似文献
15.
Qian Zhang Letong Liu Jiqiong Jiang Jian Wang 《Journal of Physics and Chemistry of Solids》2009,70(7):1080-1082
Triclinic LiVPO4F/C composite materials were prepared from a sucrose-containing precursor by one-step heat treatment. As-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements. XRD studies showed that Li3PO4 impurity phase appeared in the sample synthesized at 600 °C and pure LiVPO4F samples could be obtained when the sintered temperature was higher than 650 °C. The sample synthesized at 650 °C presents the highest initial discharge capacity of 132 mAh g−1 at 0.2 C rate, and exhibited better cycling stability (124 mAh g−1 at 50th cycle at 0.2 C rate) and better rate capability (100 mAh g−1 at 50th cycle under 1 C rate) in the voltage range 3.0-4.4 V. 相似文献
16.
Chemical spray pyrolysis was applied to grow ZnO nanorod arrays from zinc chloride solutions with pH=2 and 5 on glass/ITO substrate at 480 and 550 °C. The obtained structures were characterized by their morphological, electrical and PL properties. According to SEM, deposition of acidic solutions retards coalescence of the growing crystals. The charge carrier density in ZnO nanorods was determined from the C-V characteristics of ZnO/Hg Schottky barrier. Carrier densities ∼1015 cm−3 and slightly above 1016 cm−3 were recorded for ZnO deposited at 550 and 480 °C, respectively. According to PL studies, intense UV-emission is characteristic of ZnO independent of growth temperature, the concentration of oxygen vacancy related defects is lower in ZnO nanorods deposited at 550 °C. Solution pH has no influence on carrier density and PL properties. 相似文献
17.
Five-layered Si/SixGe1−x films on Si(1 0 0) substrate with single-layer thickness of 30 nm, 10 nm and 5 nm, respectively were prepared by RF helicon magnetron sputtering with dual targets of Si and Ge to investigate the feasibility of an industrial fabrication method on multi-stacked superlattice structure for thin-film thermoelectric applications. The fine periodic structure is confirmed in the samples except for the case of 5 nm in single-layer thickness. Fine crystalline SixGe1−x layer is obtained from 700 °C in substrate temperature, while higher than 700 °C is required for Si good layer. The composition ratio (x) in SixGe1−x is varied depending on the applied power to Si and Ge targets. Typical power ratio to obtain x = 0.83 was 7:3, Hall coefficient, p-type carrier concentration, sheet carrier concentration and mobility measured for the sample composed of five layers of Si (10 nm)/Si0.82Ge0.18 (10 nm) are 2.55 × 106 /°C, 2.56 × 1012 cm−3, 1.28 × 107 cm−2, and 15.8 cm−2/(V s), respectively. 相似文献
18.
Yang Liu Jinghai Yang Qingfeng Guan Lili Yang Yongjun Zhang Dandan Wang Yanting Yang Maobin Wei 《Applied Surface Science》2010,256(11):3559-3562
The Cr-doped zinc oxide (Zn0.97Cr0.03O) nanoparticles were successfully synthesized by sol-gel method. The relationship between the annealing temperature (400 °C, 450 °C, 500 °C and 600 °C) and the structure, magnetic properties and the optical characteristics of the produced samples was studied. The results indicate that Cr (Cr3+) ions at least partially substitute Zn (Zn2+) ions successfully. Energy dispersive spectroscopy (EDS) measurement showed the existence of Cr ion in the Cr-doped ZnO. The samples sintered in air under the temperature of 450 °C had single wurtzite ZnO structure with prominent ferromagnetism at room temperature, while in samples sintered in air at 500 °C, a second phase-ZnCr2O4 was observed and the samples were not saturated in the field of 10000 Oe. This indicated that they were mixtures of ferromagnetic materials and paramagnetic materials. Compared with the results of the photoluminescence (PL) spectra, it was reasonably concluded that the ferromagnetism observed in the studied samples was originated from the doping of Cr in the lattice of ZnO crystallites. 相似文献
19.
Z. Messaï Z. Ouennoughi T. Mouet V. Harel N. Bouguechal 《Applied Surface Science》2010,257(2):616-621
In this paper we study nanocrystalline zinc oxide thin films produced by oxidation of electrodeposited zinc nanolayers on a monocrystalline p-Si(1 1 1) substrate.The electrolyte used is ZnCl2, an aqueous solution of 4 × 10−2 mol/l concentration. Several deposits were made for various current densities, ranging from 13 mA/cm2 to 44 mA/cm2, flowing through the solution at room temperature. A parametric study enabled us to assess the effect of the current density on nucleation potential and time as well as zinc films structure. The grazing incidence X-ray diffraction (GIXD) revealed that both Zn and ZnO films are polycrystalline and nanometric. After 1-h oxidation of zinc films at 450 °C in the open air, the structural analyses showed that the obtained ZnO films remained polycrystalline with an average crystal size of about 47 nm and with (1 0 0), (0 0 2) and (1 0 1) as preferential crystallographic orientations. 相似文献
20.
Porous Ni-YSZ (YSZ—yttria-stabilized zirconia) films were fabricated by reactive co-sputtering of a Ni and a Zr-Y target, followed by sequentially annealing in air at 900 °C and in vacuum at 800 °C. The Ni-YSZ films comprised small grains and pores that were tens of nanometers in size. The porous Ni-YSZ films were used as an anode on one side of a YSZ electrolyte disc and a La0.7Sr0.3MnO3 thick film was used as a cathode on the other side of the disc to form solid oxide fuel cells (SOFCs). The voltage-current curves of the SOFCs with single- and a triple-layered porous anodes were measured in a single-chamber configuration, in a mixture of CH4 and air (CH4:O2 volume ratio=2:1). The maximum power density of the SOFC using the single-layered porous Ni-YSZ thin films as the anode was 0.38 mW cm−2, which was lower than that of 0.76 mW cm−2, obtained using a screen-printed Ni-YSZ thick anode. The maximum power density of the SOFC with a thin anode was increased, but varied between 0.6 and 1.14 mW cm−2 when a triple-layered porous Ni-YSZ anode was used. 相似文献