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1.
Chu Minh Ngo Hieu Duy Nguyen Nobuo Saito Thi Mai Dung Do Tadachika Nakayama Koichi Niihara Hisayuki Suematsu 《Journal of the American Ceramic Society》2022,105(3):1622-1628
β-MoO3 is a monoclinic phase of MoO3; it has been shown to be a promising material that can replace α-MoO3 in chemical, optical, electronic, and electrochromic applications. However, the difficulty in synthesizing β-MoO3 with a one-dimensional (1D) morphology has limited its use in applications requiring a large specific surface area. In the present work, β-MoO3 whiskers were prepared by thermally evaporating α-MoO3 powder in a tube furnace at temperatures (Tf) from 750 to 1000°C and under flowing O2 gas. The collected samples were identified as mainly β-MoO3 by X-ray diffraction measurements, and the highest purity β-MoO3 was obtained at Tf = 1000°C. Scanning and transmission electron microscopy observations showed that whiskers with a width of 10 nm were successfully synthesized by this method. The whiskers were confirmed to be β-MoO3 via lattice image analysis. Measurements of the temperature distribution in the tube furnace and comparisons with the Mo–O phase diagram led to the conclusion that the whiskers formed via a vapor–solid route. Prepared β-MoO3 whiskers were compared with α-MoO3 powder via the X-ray photoelectron spectroscopy characterization method. By elucidating the β-MoO3 whisker synthesis mechanism, this research provides guidance for the large-scale production of β-MoO3 whiskers. 相似文献
2.
Yongxia Miao Guanzhong Lu Xiaohui Liu Yanglong Guo Yanqin Wang Yun Guo 《Journal of Industrial and Engineering Chemistry》2010,16(1):45-50
The MoO3/SiO2 catalysts containing different surface molybdenum species were prepared by a sol–gel method, and the effects of the preparation condition and MoO3 loading on the surface molybdenum species and property of MoO3/SiO2 were studied. The XRD, FT-IR, UV–vis and Raman spectroscopies were used to characterize the surface molybdenum species, and temperature-programmed desorption of NH3 adsorbed on a catalyst was used to detect the surface acidic properties. The results show that, there were the dispersed polymolybdate, α-MoO3, β-MoO3, monomeric molybdenum species and silicomolybdic acid on the MoO3/SiO2 catalyst, and their distributions and subsistence states were affected by the preparation condition and MoO3 loading. Different molybdenum species exhibit different catalytic activities for the epoxidation of propylene with cumene hydroperoxide. In the 15 wt% MoO3/SiO2 catalyst synthesized at pH 9.1 and dried appropriately, there are the small size β-MoO3 and monomeric molybdenum species that they are mainly effective catalyst components for the epoxidation of propylene. Using this catalyst, the ~100% conversion of cumene hydroperoxide and ~100% selectivity to propylene oxide can be obtained in the tert-butyl alcohol solvent at 2.6 MPa and 80 °C for 4 h. 相似文献
3.
F. Chandoul A. Boukhachem F. Hosni H. Moussa M.S. Fayache M. Amlouk R. Schneider 《Ceramics International》2018,44(11):12483-12490
Thin films of Molybdenum trioxide (MoO3) were deposited on glass substrates by the spray pyrolysis at 500?°C and the samples were then exposed to gamma γ radiation doses by 60Co radioisotope at different doses (0.1, 10 and 50 kGy). The effects of gamma irradiation on the properties of MoO3 thin films were investigated. The XRD pattern and Raman spectroscopy of as-deposited MoO3 samples show an orthorhombic structure related to α-MoO3 with (0k0) preferred orientations. Uv‐vis spectra were studied to investigate the transmission measurements of MoO3 films. The optical energy band gap and Urbach energy were found to be gamma-dose dependent. Photoluminescence measurements at room temperature using 300?nm wavelength excitation were investigated. SEM images indicate the formation of α-MoO3 nanorods. 相似文献
4.
Jobin Varghese Tuomo Siponkoski Mikko Nelo Mailadil Thomas Sebastian Heli Jantunen 《Journal of the European Ceramic Society》2018,38(4):1541-1547
The α-MoO3 ceramics were prepared by uniaxial pressing and sintering of MoO3 powder at 650 °C and their structure, microstructure, densification and sintering and microwave dielectric properties were investigated. The sintering temperature of α-MoO3 was optimized based on the best densification and microwave dielectric properties. After sintering at 650 °C the relative permittivity was found to be 6.6 and the quality factor was 41,000 GHz at 11.3 GHz. The full-width half-maximum of the A1g Raman mode of bulk α-MoO3 at different sintering temperatures correlated well with the Qf values. Moreover, the sintered samples showed a temperature coefficient of the resonant frequency of ?25 ppm/°C in the temperature range from ?40 to 85 °C and they exhibited a very low coefficient of thermal expansion of ±4 ppm/°C. These microwave dielectric properties of α-MoO3 will be of great benefit in future MoO3 based materials and their applications. 相似文献
5.
《Ceramics International》2023,49(7):10714-10721
Orthorhombic Sc2(MoO4)3 nanofibers have been prepared by ethylene glycol assisted electrospinning method. The effects of annealing temperature, precursor concentration, spinning distance and solvent on the preparation of Sc2(MoO4)3 nanofibers were characterized by XRD, SEM, HRTEM, EDX and high-temperature XRD. XRD analysis shows as-prepared nanofibers are amorphous. Orthorhombic Sc2(MoO4)3 nanofibers can be fabricated after annealing at different temperatures in 500–800 °C for 2 h. The crystallinity of Sc2(MoO4)3 nanofibers improves and the nanofiber diameter decreases gradually as the annealing temperature increases. However, the nanofiber structure was destroyed at the annealing temperature above 700 °C. Higher precursor concentration results in a slight increase of diameter and decrease in destroying temperature of Sc2(MoO4)3 nanofibers. Spinning distance also affects the diameter of nanofibers, and the nanofiber diameter decreases as the distance increases. One-dimensional orthorhombic Sc2(MoO4)3 nanofibers exhibit anisotropic negative thermal expansion. In 25–700 °C, the coefficients of thermal expansion (CTE) of αa, αb and αc are ?5.81 × 10?6 °C?1, 4.80 × 10?6 °C?1 and -4.33 × 10?6 °C?1, and the αl of Sc2(MoO4)3 nanofibers is ?1.83 × 10?6 °C?1. 相似文献
6.
《Ceramics International》2016,42(16):18318-18323
MoS2 thin films were prepared by radio frequency (RF) magnetron sputtering and then annealed in air. X-ray diffraction (XRD), field-emission electron scanning microscopy (FESEM) and transmission electron microscopy (TEM) were adopted to characterize the phase structure and surface morphology. Interestingly, upon thermal annealing in air, MoS2 thin films changed into α-MoO3 with mazy morphology, and the thin films were covered by MoO3 nano-sheets with a length of 30–50 nm and a width of 10 nm. α-MoO3 thin films with mazy morphology showed excellent response to NO gas at room temperature. The response of 5% and 92% was obtained at 5 ppm and 200 ppm, respectively, and the response and recovery times were 30 s and 1500 s. Moreover, the mazy structure of MoO3 exhibited good selectivity to NO gas with respect to SO2, NH3 and H2 gases. The high surface-to-volume ratio was the dominant factor for high sensing performance. 相似文献
7.
《Ceramics International》2022,48(7):9817-9823
Electrical and optical properties of In-Ga-Sn-O (IGTO) thin films deposited by radio-frequency magnetron sputtering were investigated according to annealing temperatures. While IGTO films remained an amorphous phase even after a heat treatment at temperature up to 500 °C, Hall measurements showed that annealing temperature had a significant impact on electrical properties of IGTO thin films. After investigating a wide range of annealing temperatures for samples from as-deposited state to 500 °C, IGTO film annealed at 200 °C exhibited the best electrical performance with a conductivity of 229.31 Ω?1cm?1, a Hall mobility of 36.89 cm2V?1s?1, and a carrier concentration of 3.85 × 1019 cm?3. Changes in proportions of oxygen-related defects and percentages of Sn2+ and Sn4+ ions within IGTO films according to annealing temperatures were analyzed with X-ray photoelectron spectroscopy to determine the cause of the superb performance of IGTO at a low temperature. In IGTO films annealed at 200 °C, Sn4+ ions acting as donor defects accounted for a high percentage, whereas hydroxyl groups working as electron traps showed a significantly reduced percentage compared to the as-deposited film. Optical band gaps of IGTO films obtained from UV–visible spectrum were 3.38–3.47 eV. The largest band gap value of 3.47 eV for the IGTO film annealed at 200 °C could be attributed to an increase in Fermi-level due to an increase of carrier concentration in the conduction band. These spectroscopic results well matched with electrical properties of IGTO films according to annealing temperatures. Excellent electrical properties of IGTO thin films annealed at 200 °C could be largely due to Sn donors besides oxygen vacancies, resulting in a significant increase in free carriers despite a low annealing. temperature. 相似文献
8.
《Ceramics International》2022,48(11):15380-15389
In the present study, the effect of thermal annealing on structural, linear, and nonlinear optical properties of quaternary chalcogenide In15Ag10S15Se60 thin film has been reported. The bulk sample synthesized by the melt quenching technique was used for the thin film preparation by the thermal evaporation method. Post deposition, the thin films were annealed at different temperatures like 100 °C, 150 °C, 200 °C, and 250 °C for 2 hs. X-ray diffraction (XRD) and Raman spectroscopy were used for structural studies, which showed the increase in crystalline phases with the increase of annealing temperature. The morphological images taken by field emission scanning electron microscope (FESEM) showed the densification and enlargement of scattered grains for annealed films. Furthermore, the constituent elements and their percentage in the sample were confirmed by Energy dispersive X-ray analysis (EDX). The linear and nonlinear optical parameters were calculated from the transmittance data obtained from UV–Vis spectroscopy in the wavelength range of 600–1100 nm. There is a large reduction in third-order nonlinear susceptibility at the higher annealing temperature. Subsequently, the transmission increased, whereas the absorption decreased with the annealing temperature. The extinction coefficient decreased while there was an increase in optical bandgap for the annealed films due to the decrease in surface defects and disorder, which forms the localized states in the bandgap. The oscillator energy, dispersion energy, dielectric constant, optical conductivity were calculated and discussed in detail. The change in both linear and nonlinear parameters by thermal annealing could be useful for controlling the optical properties of In15Ag10S15Se60 thin film, which could be the preferable candidate for numerous photonic applications. 相似文献
9.
Thin films with the composition 70 mol% Na0.5Bi0.5TiO3 + 30 mol% NaTaO3 were prepared by sol–gel synthesis and spin coating. The influence of the annealing temperature on the microstructural development and its further influence on the dielectric properties in the low‐ (kHz–MHz) and microwave‐frequency (15 GHz) ranges were investigated. In the low‐frequency range we observed that with an increasing annealing temperature from 550°C to 650°C the average grain size increased from 90 to 170 nm, which led to an increase in the dielectric permittivity from 130 to 240. The temperature‐stable dielectric properties were measured for thin films annealed at 650°C in the temperature range between ?25°C and 150°C. The thin films deposited on corundum substrates had a lower average grain size than those on Si/SiO2/TiO2/Pt substrates. The highest average grain size of 130 nm was obtained for a thin film annealed at 600°C, which displayed a dielectric permittivity of 130, measured at 15 GHz. 相似文献
10.
《Journal of the European Ceramic Society》2007,27(13-15):3815-3818
ZnO thin films were successfully deposited on SiO2/Si substrate by sol–gel technology. The as-grown ZnO thin films were annealed under an ambient atmosphere from 600 to 900 °C by rapid thermal annealing (RTA) process. X-ray diffraction and scanning electron microscopy analyses reveal the physical structures of ZnO thin films. From PL measurement, two ultraviolet (UV) luminescence bands were obtained at 375 and 380 nm, and the intensity became stronger when the annealing temperature was increased. The strongest UV light emission appeared at annealing temperature of 900 °C. The chemical bonding state in ZnO films was investigated by using X-ray photoelectron spectrum. The mechanism of UV emission was also discussed. 相似文献
11.
Hiroaki Nakade Eita Tochigi Bin Feng Ryo Ishikawa Hiromichi Ohta Naoya Shibata Yuichi Ikuhara 《Journal of the American Ceramic Society》2022,105(3):2300-2308
In order to fabricate tetragonal yttria stabilized zirconia samples with large grain size, 3 mol% Y2O3 doped zirconia thin films were grown on (0001) α-Al2O3 substrate by pulsed laser deposition (PLD) followed by subsequent high temperature annealing. The thin film samples were annealed at 1200°C, 1250°C, 1300°C, and 1350°C in order to obtain larger grain size without Y segregation. The microstructure and chemical composition of these annealed films were analyzed using atomic force microscopy, scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The as-grown thin film was found to be composed of [111]-oriented grains of ∼100 nm connected with small-angle tilt boundaries. Based on analysis of annealed thin films, it was revealed that grain growth of tetragonal zirconia occurred anisotropically. Cross section scanning transmission electron microscopy observations revealed that such grain growth behavior is affected by the step-terrace structures of the sapphire substrate. Energy-dispersive X-ray spectroscopy showed that Y was found to distribute almost uniformly below 1300°C but to segregate at the grain boundaries at 1350°C. As a conclusion, the 1300°C-annealed sample shows the largest grain size with homogeneous Y distributions. 相似文献
12.
《Ceramics International》2016,42(7):8636-8644
Effects of oxidation cross-linking and sintering additives (TiN, B) on the microstructure formation and heat-resistant performance of freestanding SiC(Ti, B) films synthesized from Ti, B-containing polycarbosilane (TiB-PCS) precursor were investigated. TiB-PCS green films were first cross-linked for 1 h, 2 h, 3 h and 4 h, respectively, and then pre-sintered at 950 °C. Finally, they were sintered at 1800 °C to complete the conversion from organic films to inorganic SiC(Ti, B) films. The results reveal that curing time has a great impact on the uniformity and density of SiC(Ti, B) films. TiB-PCS films cured for 3 h yield the best quality SiC(Ti, B) films, which are composed of β-SiC crystals, C clusters, α-SiC nano-crystals, a small amount of TiB2 and B4C. TiB2 and B4C are both steady phases which can inhibit abnormal growth of β-SiC, effectively reduce sintering temperature and help consume excess C from decomposition of amorphous SiOxCy. After high temperature annealing at 1500 °C, 1600 °C and 1700 °C in argon, SiC(Ti, B) films still keep excellent mechanical properties, which makes them attractive candidate materials for microelectromechanical systems (MEMS) used at ultra-high temperatures (exceeding 1500 °C). 相似文献
13.
《Ceramics International》2023,49(18):29534-29541
Tungsten trioxide (WO3) is a classical electrochromic (EC) material with advantages of abundant reserves, high coloration efficiency and cyclic stability. However, WO3 films are often accompanied by a narrow spectrum of modulation due to a single-color change from transparent to blue. In this work, we report a wide-spectrum tunable WO3·H2O nanosheets EC film solvothermally grown on fluorine-doped tin oxide (FTO) glass. Interestingly, the crystalline WO3·H2O nanosheets film is transformed into amorphous WO3 after annealing at 250 °C for 1 h. The amorphous film can be transformed into crystalline WO3 film by increasing the annealing temperature to 450 °C. After annealing at 250 °C, the WO3 film exhibits an optical modulation of 75.8% in a broad solar spectrum range of 380–1400 nm and blocks 88.9% of solar irradiance. Fast switching responses of 4.9 s for coloration and 6.0 s for bleaching, and a coloration efficiency of 86.4 cm2 C−1 are also achieved. Additionally, the WO3 film annealed at 250 °C also demonstrates an excellent cyclic stability, where 99.6% of the initial optical modulation can be retained after 1500 cycles. This simple and mild solvothermal method used in this work provides a new idea for the preparation of wide-spectrum tunable WO3 EC films. 相似文献
14.
《Ceramics International》2022,48(14):20078-20089
The growth of crack-free nanostructured NiO films with good crystalline quality is of high importance for photodetectors to avoid performance failure. In this work, physical properties of spin coated NiO films were controlled by changing diethanolamine (DEA) to nickel acetate (NiAc) molar ratio (0:1–1:1) and post annealing temperature (300–650 °C). NiO film coated at DEA:NiAc molar ratio of 0:1 suffered from severe cracks and poor crystallinity, and by increasing the molar ratio to 1:1 a crack-free NiO with enhanced grain growth was obtained. With the increase of annealing temperature from 300 C to 600 °C, the crystallite size increased from 12.79 to 37.31 nm, and the bandgap decreased from 3.81 to 3.42 eV, indicating an enhancement in NiO film quality. A self-powered photodetector based on p-NiO/n-Si heterojunction showed broadband (UV-NIR) photodetection owing to synergistic photoelectric effect from both NiO film and Si substrate. The responsivity, detectivity, and external quantum efficiency were measured as 13.08, 46.02, 44.49, mA/W, 1.03 × 1011, 3.65 × 1011, 3.53 × 1011, Jones, and 4.43%, 8.62%, 6.47% upon illumination with UV (365 nm), red (660 nm), and NIR (850 nm) lights, respectively. The photodetector showed high on/off current ratio of 1.210 × 103 and fast response (less than 85 ms). These findings introduce p-NiO/n-Si heterojunction as a promising candidate for next generation optoelectronics. 相似文献
15.
《Ceramics International》2016,42(3):3882-3887
The effect of annealing on structural and magnetic properties of the RF sputtered BaTiO3 and Co, Nb co-doped BaTiO3 thin films on Si (001) substrates were studied. The structure of the as-deposited (amorphous) films was changed into cubic perovskite phase during the in-situ X-ray diffraction from room temperature to 900 °C. The enhancement of crystalline quality with respect to the increase of annealing temperature was observed by the in-situ XRD. The magnetic properties of the films before and after annealing were studied by the measurement of Magneto-Optic Kerr Effect (MOKE). The pure BaTiO3 revealed a paramagnetic behavior, whereas the Co and Nb co-doped BaTiO3 films exhibited room temperature ferromagnetism. The increase in ferromagnetic response was observed in the Co and Nb co-doped BaTiO3 films annealed at 900 °C rather than the as-deposited film. 相似文献
16.
Chun-Kai Wang Diptiranjan Sahu Sheng-Chang Wang Jow-Lay Huang 《Ceramics International》2012,38(4):2829-2833
The Nb-doped WO3 films were deposited by e-beam co-evaporation method using ceramic WO3 targets and metal Nb slugs. The films were analyzed by glancing incident angle X-ray diffraction (GIAXRD), UV/visible spectrophotometer, electrochemical cyclic voltammetry, X-ray photoelectron spectroscopy (XPS). The as-prepared film is brown and amorphous in structure. The film has low transmission in optical visible region. The XPS results indicate that the as-deposited film is non-stoichiometric. By applying a negative potential, the as-deposited film does not show obvious electrochromic effect. However, the electrochromic properties of Nb-doped WO3 films are improved by post annealing treatment at 350, 400, and 450 °C in oxygen atmosphere. The Nb-doped WO3 films transform into crystalline structure and become transparent after post annealing treatment. The energy band gap, optical modulation, and color efficiency increase with annealing temperature. 相似文献
17.
《Ceramics International》2016,42(11):13065-13073
A mixture of α/β-Bi2O3 and α-Bi2O3 powders were obtained by a simple solid state reaction–annealing route at 550 °C. The structure, optical properties and surface area of the commercial α and β-Bi2O3 and the synthesized α-phase and α/β-composite were well characterized by X-ray diffraction, diffuse reflectance spectra and N2 physisorption. The annealed sample at 550 °C showed 20% of β-phase, forming a heterojunction of α/β-Bi2O3 whereas annealing at elevated temperature (650 °C) lead to the α-phase. Optical properties showed that the presence of the β-phase is mainly responsible for narrowing the energy band gap. The photocatalytic activity of the commercial α and β-Bi2O3 and the synthesized α-phase and α/β-composite were investigated in degradation of single dyes, Indigo Carmine (IC) and Rhodamine-B (RhB) under both UV and visible light-induced photocatalysis. For the best photocatalyst, the photodegradation in a two-dye mixture solution was systematically studied considering the type of dye, the adsorption capacity of the samples and the behavior of dye photodegradation. The photocatalytic performance of α/β-Bi2O3 was comparatively much higher than the commercial α and β-Bi2O3, indicating that better performance of efficient charge separation and transfer across α/β-Bi2O3 composite was obtained. Possible mechanism of the single dye and two-dye mixture degradation was given by using α/β-Bi2O3 composite. 相似文献
18.
With the integrative transformation of non α-tocopherols, glycerides, free fatty acids, and methyl alcohol in cottonseed oil deodorizing distillate as the target reaction, we prepared highly catalytic SO42?/ZrO2-MoO3 solid acid catalyst by precipitation–wet impregnation. The optimal conditions for catalyst preparation were then determined by varying sulfuric acid concentration, MoO3 loading factor, calcination temperature, and calcination time. The structure of SO42?/ZrO2-MoO3 solid acid catalyst was then examined by X-ray diffraction (XRD), Brunauer–Emmett–Teller measurements, scanning electron microscopy, and other methods. Results show that the MoO3 loading factor (percentage weight ratio of MoO3 to ZrO2), impregnation concentration of sulfuric acid, and calcination temperature were the most important factors that influenced catalytic activity. The optimal conditions for catalyst preparation were an MoO3 loading factor of 20%, a sulfuric acid impregnation concentration of 0.75 mol/L, a calcination temperature of 550 °C, and a calcination time of 6 h. The obtained catalyst exhibited the highest catalytic activity under these conditions. 相似文献
19.
《Journal of the European Ceramic Society》2023,43(8):3318-3323
The Li2MoO4-MoO3 ceramic system can be densely sintered at ultralow temperatures (< 500 °C). However, the phase composition of the Li2MoO4-MoO3 system at a molar ratio of 1:1 has always been controversial. In this study, the traditional solid-state method was used to synthesize Li4Mo5O17 (400 °C, 10 h) and Li2Mo2O7 (350–400 °C, 4 h). Li2Mo2O7 is an intermediate phase that can be converted to Li4Mo5O17 at higher temperatures. The Li4Mo5O17 ceramic could be sintered and densified at only 490 °C in air, exhibiting a relative density of 95.6% and excellent dielectric properties, including ε′= 12.79 and tan δ = 0.0004 at 1 GHz. Such an ultralow sintering temperature and dielectric loss indicate that the Li4Mo5O17 ceramic is a good candidate for high-frequency capacitance applications. 相似文献
20.
《Journal of the European Ceramic Society》2023,43(6):2534-2540
An aerosol deposition method was used to fabricate a solar-blind photodetector (for UV-C) using thin films of β-Ga2O3, which is a wide-bandgap oxide material. The Ga2O3 films deposited at room temperature presented a polycrystalline structure and a thickness of approximately 4 µm and showed a high transmittance of approximately 70–80 % in the visible region; the transmittance was approximately 60–80 % even after heat treatment up to a 800 °C. The Ga2O3 films that were post-annealed at a temperature of 800 °C showed an Iphoto/Idark ratio of approximately 40,000 in the solar-blind region with a light source of 254 nm, together with very good light detection characteristics (initial rising and decay times of 0.45 s and 0.13 s, respectively). Because of the good performances observed for the Ga2O3 thin films even at extreme conditions, they exhibit a high potential for use as photodetectors in several applications. 相似文献