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1.
This work examines the synthesis and characterization of crack‐free, β‐Bi2O3 thin films prepared on Pt/TiO2/SiO2/Si or corundum substrates using the sol‐gel method. We observed that the Bi‐based precursor has a pronounced influence on the β‐Bi2O3 phase formation. Well‐crystallized, single β‐Bi2O3 thin films were obtained from Bi‐2ethylhexanoate at a temperature of 400°C. In contrast, thin films deposited from Bi‐nitrate and Bi‐acetate resulted in non‐single Bi2O3 phase formation. TEOS was used for the stabilization of the β‐Bi2O3 phase. The phase composition of the thin films was characterized by means of X‐ray diffraction (XRD), whereas the morphology and thickness of the thin films were studied using scanning electron microscopy (SEM). The β‐Bi2O3 films' dielectric properties were characterized utilizing microwave‐frequency measurement techniques: (1) the split‐post dielectric resonator method (15 GHz) and (2) the planar capacitor configuration (1–5 GHz). The dielectric constant and dielectric loss measured at 15 GHz were 257 and 7.5 × 10?3, respectively. 相似文献
2.
Huanchun Wang Haomin Xu Chengcheng Zeng Yang Shen Yuan‐Hua Lin Ce‐Wen Nan 《Journal of the American Ceramic Society》2016,99(4):1133-1136
Pure perovskite BiFeO3, sillenite Bi2Fe4O9, and BiFeO3/Bi2Fe4O9 were synthesized facilely by controlling the precursor Bi/Fe ion ratio through a hydrothermal method. The phase composition, morphology, optical properties, and photocatalytic activity of as‐prepared samples were investigated in detail. Our results indicate that the morphology and properties of products strongly dependent on the precursor Bi/Fe ion ratio. Photocatalysis of Congo Red reveals that sillenite Bi2Fe4O9 shows superior activity to perovskite BiFeO3, and BiFeO3/Bi2Fe4O9 exhibited higher activity with 71.45% degradation rate in 90 min. It provides an easy and efficient way to tune the composition and photocatalytic activity of Bi‐based oxides. 相似文献
3.
Synthesis,structural characterization,and photocatalytic activity of Bi‐based nanoparticles
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Adriana Nuñez‐Briones Luis García‐Cerda Joelis Rodríguez‐Hernández Miguel Aguilar‐González Bertha Puente‐Urbina Esmeralda Mendoza‐Mendoza 《International Journal of Applied Ceramic Technology》2018,15(1):101-110
Bi‐based nanoparticles were successfully synthesized (500°C/2 h) following two intermediate‐temperature routes, Pechini and a combined method of mechanical milling/molten salts. Herein, α‐Bi2O3/Bi2O2CO3 heterostructures were identified. These types of heterostructures have shown advantages to improve the visible light responsive activity of Bi‐based nanoparticles to facilitate the separation of photogenerated electron‐hole pairs. By fixing the experimental parameters, the synthesis route and Ag contents showed to play a very important role in the phase composition of the Ag‐containing samples; the formation of Bi/Ag‐Bi2O3/Bi2O2CO3 and Ag/Ag‐Bi2O3/Bi2O2CO3 complex hybrid structures were revealed. The α‐Bi2O3/Bi2O2CO3 heterostructure prepared by combined method exhibited higher photocatalytic efficiency (66.84%) for degrading methylene blue (MB) depending on Bi2O2CO3 component proportion. For the Ag‐containing hybrid structures, the performance of their catalytic activity did not show an increase with respect to α‐Bi2O3/Bi2O2CO3. However, in these samples, the degradation efficiency was slightly enhanced with the efficient doping of Ag into the α‐Bi2O3 structure and the existence of Bi when the Pechini method was used. Also, a possible photocatalytic process for degrading MB is presented. 相似文献
4.
Ahmad Hussain Muhammad Adnan Qaiser Ji Zhang Shan‐Tao Zhang Yiping Wang Ying Yang Zhiguo Liu Guoliang Yuan 《Journal of the American Ceramic Society》2017,100(8):3522-3529
The 0‐3 type CaBi4Ti4O15:30 wt%BiFeO3 composite shows much better high‐temperature piezoelectric properties than the single‐phase CaBi4Ti4O15 or BiFeO3 ceramics. The composite with 0‐3 type connectivity exhibits a high density of 7.01 g/cm3, a saturated polarization of 21.5 μC/cm2 and an enhanced piezoelectric d33 of 25 pC/N. After the poled composite was annealed at 600°C, its d33 is 21 pC/N at room temperature. Resistance of the composite decreases slowly from 109 ohm at 20°C to ~105 ohm at 500°C. Furthermore, the poled composite shows strong radial and thickness dielectric resonances at 20°C‐500°C. 相似文献
5.
A. Hardy S. Gielis H. Van den Rul J. D’Haen M.K. Van Bael J. Mullens 《Journal of the European Ceramic Society》2009,29(14):3007-3013
Phase pure BiFeO3 powders are synthesized by an entirely aqueous solution–gel route, starting from water soluble Fe(III) nitrate or citrate, and Bi(III) citrate as precursors. In order to obtain stable solutions, which transform to homogeneous gels upon drying, the pH is adjusted to 7 and a citric acid content equimolar to the metal ions is selected.The presence of nitrate strongly accelerates the thermo-oxidative decomposition step of the precursor gel around 200 °C, and the decomposition is finished at a lower temperature for the nitrate containing precursor (460 °C) than without nitrates (500 °C) in dynamic dry air. An oxidative ambient is required to fully decompose the precursor.The presented synthesis allows very low temperature (400 °C) crystallization of BiFeO3 together with a secondary phase, as shown by high temperature XRD. This parasitic phase remains up to high temperatures, where decomposition of BiFeO3 is observed from 750 °C onwards, and Bi2Fe4O9 is formed. However, optimization of the furnace treatment, considering anneal temperatures and heating rates showed that phase pure BiFeO3 can be obtained, with the heating rate being the crucial factor (5 °C/min). The chemical purity of the powders is confirmed by FTIR, and the antiferromagnetic to paramagnetic phase transition is demonstrated by DSC measurements. 相似文献
6.
Preparation and electrical properties of ZnO‐Bi2O3‐based multilayer varistors with base metal nickel inner electrodes
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Tao Chen Hao Zu Chao Gao Chunfeng Ke Dongxiang Zhou Yunxinag Hu Zhiping Zheng Qiuyun Fu 《Journal of the American Ceramic Society》2017,100(7):3024-3032
In this study, ZnO‐Bi2O3‐based multilayer varistors (MLVs) cofired with nickel (Ni) inner electrodes were prepared by tape‐casting method. Samples were sintered in pure nitrogen (N2) to keep Ni from being oxidized, and then reoxidized in air to obtain the nonlinear properties (reduction‐reoxidation method). The EDAX results showed that Ni inner electrodes are stable and have no evident migration into ZnO‐Bi2O3‐based ceramics when sintered in N2. The influence of reoxidation temperature on microstructures and nonlinear properties of samples were studied. Samples reoxidized at the temperatures lower than 650°C showed poor nonlinear properties. After reoxidized in air at 700°C for 2 hours, samples exhibited nonlinear properties of V1 mA=16.3 V, α=26.5, IL=0.68 μA. At the reoxidation temperature higher than 750°C, the oxidation of Ni inner electrodes deteriorated the nonlinear properties of samples. It demonstrated that ZnO‐Bi2O3‐based MLVs with base metal Ni inner electrodes proposed in this work are suitable for reduction‐reoxidation method. The replacement of noble metals Pt or Ag/Pd alloys by base metal Ni is expected to lower the cost of ZnO‐Bi2O3‐based MLVs. 相似文献
7.
T. N. Patrusheva A. S. Aleksandrovskii A. A. Khval’ko Yu. V. Kolovskii A. V. Polyushkevich A. I. Khol’kin 《Theoretical Foundations of Chemical Engineering》2012,46(4):379-383
Luminescent Y1.74Eu0.16Bi0.1O3 films have been obtained by extraction pyrolytic method. The formation of a crystalline structure in the film upon isothermal annealing in air at 600?C650°C was established by X-ray diffraction. Single-phase Y1.74Eu0.16Bi0.1O3 films begin to exhibit luminescent properties after pyrolysis at 500°C; the intensity of luminescence increases with increasing temperature. The films annealed at 800°C consists of defect-free homogeneous crystallites with sizes of about 0.7 ??m and demonstrats high luminescence intensity. 相似文献
8.
《Journal of the European Ceramic Society》2019,39(2-3):330-339
Bi2Fe4O9 was prepared by solid-state reaction and the electrical properties measured by impedance spectroscopy. After annealing in O2 at 900 °C, Bi2Fe4O9 is an electrically-homogeneous insulator. Its high frequency permittivity is constant (∼14.1) over the temperature range 300–400 °C and shows no evidence of incipient ferroelectricity at lower temperatures. On annealing in N2 at 900 °C, the pellets gradually decompose.Bi25FeO39 was prepared by both solid-state reaction and mechanosynthesis. It showed a modest amount of mixed conduction of both oxide ions and holes. Impedance analysis showed a complex response that best fitted an equivalent circuit consisting of a parallel combination of long-range conduction and short range dielectric relaxation elements.The electrical conductivity of both Bi2Fe4O9 and Bi25FeO39 is less than that of BiFeO3 prepared by solid-state reaction, which indicates that any leakage conductivity of BiFeO3 is not due to the possible presence of small amounts of these secondary phases. 相似文献
9.
Xinhua Zhu Jun Zhou Mengchao Jiang Jun Xie Shuang Liang Shuyi Li Zidong Liu Yingying Zhu Jianmin Zhu Zhiguo Liu 《Journal of the American Ceramic Society》2014,97(7):2223-2232
Bismuth ferrite nano‐ and microcrystals were prepared by a facile molten salt technique in two kinds of molten‐salt‐based systems (NaCl–KCl and NaCl–Na2SO4). In the NaCl–KCl salt system, a systematic study indicating the effects of process parameters (e.g., calcination temperature, holding time as well as the molten salt ratios) on the bismuth ferrite formation mechanism and structural characteristics is reported. The results show that almost pure phase BiFeO3 powders with minimum impurity phase of Bi2Fe4O9 were synthesized at temperatures of 700°C–800°C, whereas high calcination temperature (e.g., 900°C) resulted in the formation of almost pure phase Bi2Fe4O9 powders. The prolonged holding time increased the particle size via the Ostwald ripening mechanism; however, there was little effect on the particle morphology. Similar phenomenon occurred as increasing the molten salt ratios. In the NaCl–Na2SO4 salt systems, it is found that low NP‐9 (nonylphenyl ether, NP‐9) surfactant content (0–5 mL) led to the formation of almost pure phase BiFeO3 powders, whereas high NP‐9 surfactant content (e.g., 20 mL) resulted in pure phase Bi2Fe4O9 powders. The average particle size of the BiFeO3 powders was decreased as increasing the NP‐9 surfactant content, whereas their morphologies did not change significantly. Because of the simplicity and versatility of the approach used, it is expected that this methodology can be generalized to the large‐scale preparation of other important transitional metal oxides with controllable sizes and shapes. 相似文献
10.
《Ceramics International》2022,48(4):5239-5245
Ta-doped Bi3.25La0.75Ti3O12(BLTT)/ZnO films were fabricated on Pt(111)/Ti/SiO2/Si substrates by a magnetron sputtering method. Firstly, ZnO crystal thin films were grown on the substrates by a reactive sputtering method. Then, BLTT thin films were deposited on the ZnO layers at room temperature and post-annealed at 600 °C. The micromorphology, ferroelectric and dielectric properties of BLTT/ZnO films were analyzed. The XRD analysis shows that ZnO buffer layer significantly reduces the crystallization temperature of BLTT thin film. The TEM results show that lamellar BLTT grains are grown on ZnO layer at a certain angle with few elements diffusion at the interface of ZnO phase and Bi4Ti3O12 phase. The ferroelectric properties indicate that BLTT/ZnO films exhibit different remanent polarization and coercive fields under electric field with different directions. The novel mechanism of tailoring ferroelectric properties may open new possibilities for designing special ferroelectric devices. 相似文献
11.
Alfred A Susu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(6):928-942
BACKGROUND: The metal dispersed over a support can be present as small crystallites with sizes less than 5 nm. The smaller crystallites favour aromatization while larger crystallites favour cracking/hydrogenolysis. Sintering results in the agglomerization of smaller metal crystallites. Correlation of size with aromatization selectivity was investigated. RESULTS: The primary products of n‐heptane reforming on fresh Pt were methane, toluene, and benzene, while on fresh Pt‐Re, the only product was methane. Both catalysts exhibited enhanced aromatization selectivity at different oxygen sintering temperatures. The reaction products ranged from only toluene at 500 °C sintering temperature to methane at a sintering temperature of 650 °C with no reaction at 800 °C for the Pt/Al2O3 catalyst. On Pt‐Re/Al2O3 catalyst, methane was the sole product at a sintering temperature of 500 °C while only toluene was produced at a sintering temperature of 800 °C. CONCLUSION: This is the first time that sintering has been used to facilitate aromatization of supported Pt and Pt‐Re catalysts. A superior selectivity behaviour associated with bi‐metallic Pt catalysts is established. It was found that no reaction occurred on Pt catalyst after sintering at 800 °C whereas sintering Pt‐Re at 800 °C promoted aromatization solely to toluene. Copyright © 2008 Society of Chemical Industry 相似文献
12.
Alfred A Susu Emmanuel O Ogogo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(4):694-705
A platinum/alumina catalyst was sintered in oxygen and hydrogen atmospheres using two metal loadings of the catalyst: 0.3% Pt and 0.6% Pt. After sintering, the aromatization selectivity was investigated with the reforming of n‐heptane as the model reaction at a temperature of 500 °C and a pressure of 391.8 kPa. The primary products of n‐heptane reforming on the fresh platinum catalysts were methane and toluene, with subsequent conversion of benzene from toluene demethylation. To induce sintering, the catalysts were treated with oxygen at a flow rate of 60 mL min?1, pressure of 195.9 kPa and temperatures between 500 and 800 °C. The 0.3% Pt/Al2O3 catalyst exhibited enhanced aromatization selectivity at various sintering temperatures while the 0.6% Pt/Al2O3 catalyst was inherently hydrogenolytic. The fact that aromatization was absent on the 0.6% Pt/Al2O3 catalyst was attributed to the presence of surface structures with dimensionality between two and three as opposed to essentially 2‐D structures on the 0.3% Pt/Al2O3 catalyst surface. On the 0.3% Pt/Al2O3 catalyst, the reaction product ranged from only toluene at a 500 °C sintering temperature to predominantly cracked product at a sintering temperature of 650 °C and no reaction at 800 °C. For sintering at about 650 °C, subsequent conversion of n‐heptane was complete and dropped thereafter. The turnover number was observed to change from 0.07 to 2.26 s?1 as the dispersion changed from 0.33 to 0.09. The Koros–Nowark (K–N) test was used to check for the presence of internal diffusional incursions and Boudart's criterion was used for structural sensitivity determination. The K–N test indicated the absence of diffusional resistances while n‐heptane reforming was found to be structure sensitive on the Pt/Al2O3 catalyst. Copyright © 2006 Society of Chemical Industry 相似文献
13.
Mullite compounds with bismuth oxide in the SiO2–Al2O3–Bi2O3 ternary system were synthesized from TEOS (C2H5O)4Si, aluminum nitrate Al(NO3)3·9H2O and bismuth nitrate Bi(NO3)3. Thermal and structural transformations were studied at temperatures ranging from 1000 to 1400 °C. The coexistence of Al4Bi2O9 and Bi4Si3O12 phases at temperatures up to 1000 °C was observed in compositions containing 5–31 mol% Bi2O3. Mullite is observed at temperature higher than 1000 °C in composition not exceeding 5 mol% of Bi2O3. Corundum coexist with a liquid above 1000 °C in all compositions containing more than 5 mol% Bi2O3. The liquid temperature is slightly above 1000 °C for all compositions. A tentative pseudo-binary diagram mullite-Bi2O3 is proposed. A similar system was studied with silico-aluminate compositions containing kaolinite and muscovite minerals. The occurrence of a liquid when Bi2O3 is added highly favors the mullite growth at temperature below 1200 °C. It is favored by local concentrations at interfaces of a transient liquid phase, which enhance the mobility of species. 相似文献
14.
Hsing‐I Hsiang Li‐Then Mei Chi‐Shiung Hsi Wei‐Cheng Wu Jer‐Hao Wu Fu‐Su Yen 《International Journal of Applied Ceramic Technology》2013,10(1):160-167
The Bi2O3–B2O3–ZnO–SiO2 (BB35SZ) glass effects on the sintering behavior and magnetic properties of Bi–Zn co‐doped Co2Y ferrites were investigated in developing low‐temperature‐fired ferrites. The results indicate that BB35SZ glass can be used as a sintering aid to reduce the densification temperature of Co2Y ferrites from 1300°C to 900°C. The 2(Ba0.9Bi0.1O)·2(Zn0.4Co0.4Cu0.2O)·6(Fe1.97Zn0.03O3) ferrite with 4 wt% BB35SZ glass can be densified below 900°C, exhibiting an initial permeability of 3.4 and quality factor of 55. This process provides a promising candidate for multilayer chip magnetic devices for microwave applications. 相似文献
15.
Chinnambedu Murugesan Raghavan Jin Won Kim Sang Su Kim 《Journal of the American Ceramic Society》2014,97(1):235-240
Effects of Ho and Ti ions individual doping and co‐doping on the structural, electrical, and ferroelectric properties of the BiFeO3 thin films are reported. Pure BiFeO3, (Bi0.9Ho0.1)FeO3, Bi(Fe0.98Ti0.02)O3+δ, and (Bi0.9Ho0.1)(Fe0.98Ti0.02)O3+δ thin films were prepared on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method. All thin films were crystallized in distorted rhombohedral structure containing no secondary or impurity phases confirmed by using an X‐ray diffraction study. Changes in microstructural features, such as grain morphology and grain size distribution, for the doped samples were analyzed by a scanning electron microscopy. From the experimental results, a low electrical leakage (1.2 × 10?5 A/cm2 at 100 kV) and improved ferroelectric properties, such as a large remnant polarization (2Pr) of 52 μC/cm2 and a low coercive field (2Ec) of 886 kV/cm, were observed for the (Bi0.9Ho0.1)(Fe0.98Ti0.02)O3+δ thin film. Fast current relaxation and stabilization observed in the (Bi0.9Ho0.1)(Fe0.98Ti0.02)O3+δ imply effective reduction and neutralization of charged free carriers. 相似文献
16.
Determination of thermodynamic data on the formation of Bi2O3 was established by emf measurements as a function of temperature in the range 660–820°C on the system Metal, Bi(1)|Bi2O3|Pt, O2. From the results using a tungsten electrode the following relation was found: ΔG0 = ?(134.7 ± 1.2) + (64.0 ± 1.2) × 10?3 T kcal mole?1 (validity range: 940–1080 K). Standard thermodynamic data at 298 K were calculated as ΔG0 = ?119.2 ± 2.1 kcal mole?, ΔH0 = ?139.0 ± 1.2 kcal mole?1, and ΔS0 = ?66.3 ± 1.2 eu. 相似文献
17.
Development of a lead‐free copper co‐fired BNT‐based piezoceramic sintered at low temperature
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Compatibility of Bi‐based piezoelectric ceramic and copper electrodes is demonstrated by co‐firing 0.88Bi1/2Na1/2TiO3–0.08Bi1/2K1/2TiO3–0.04BaTiO3 (BNKBT88) with copper. A combination of Bi2O3, CuO, ZnO, Li2CO3, and B2O3 are used as additives to reduce firing temperature to 900°C with minimal effect on the electromechanical properties compared to sintering at 1150°C without additives. Co‐firing with copper electrodes requires controlled oxygen sintering at low temperature. The atmosphere is controlled using carbon dioxide and hydrogen gas to maintain an oxygen partial pressure of 6.1 × 10?8 atm, which is necessary for the coexistence of Cu metal and Bi2O3. The thermodynamic activity of bismuth oxide in BNKBT88 is calculated to be 0.38. BNKBT88 ceramics were successfully co‐fired with internal as well as surface Cu metal electrodes. The copper co‐fired ceramics were successfully polarized and the dielectric and piezoelectric properties are evaluated. 相似文献
18.
Effect of Concentration and Temperature on the Surface Morphology of Gd2O3 Nanocrystallites in Silica
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Rachna Ahlawat 《International Journal of Applied Ceramic Technology》2015,12(6):1131-1139
Gd(NO3)3.6H2O and TEOS were used as precursors and obtained Gd2O3:SiO2 ceramic powder having different concentration of Gd2O3 as 2.2, 2.8, 3.4, and 4.0 wt % using solgel process. The powdered samples were annealed at 500°C and 900°C temperatures and characterized by XRD, FTIR, SEM, and TEM. In X‐ray diffraction, cubic phase of Gadolinium oxide is reported only for the annealed samples having higher concentration (3.4 & 4.0 wt %) of Gd2O3. SEM and TEM results further confirm that the surface morphology of the microstructures depend on the temperature and concentration. 相似文献
19.
《Ceramics International》2019,45(16):19793-19798
Bismuth ferrite (BiFeO3, BFO) powders were synthesized by a simple and cost-effective solvent-deficient method using bismuth nitrate, iron nitrate, and ammonium bicarbonate as the only precursors. Single phase BiFeO3 powder was fabricated after the Bi:Fe ratio was adjusted and after the precursor mixture was calcined for one hour at 600 °C. We investigated the formation reactions, crystal structure, particle size distribution, magnetic and optical properties of synthesized BiFeO3. X-ray diffraction revealed the formation of well-crystallized BFO nanocrystallites starting at a temperature of 450 °C. BiFeO3 powder calcined at 600 °C showed very weak ferromagnetism at room temperature which is different from the linear M–H relationship in bulk BiFeO3 ceramics. The remnant magnetization value (Mr) was found to be 5 × 10−3 emu g−1 and a coercive field value (Hc) nearly 500 Oe. The UV–visible spectra showed maximum adsorption at ∼464 nm with a derived bandgap value of 1.85 (1.8449 ± 0.0013) eV for BFO nanocrystallites supporting their potential application as visible light-response photocatalysts. Direct bandgap value obtained from reflectance measurement is determined to be 2.25 (2.2464 ± 0.0065) eV. 相似文献
20.
Bi2O3 nanoparticles incorporated porous TiO2 films as an effective p‐n junction with enhanced photocatalytic activity
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Na Wei Hongzhi Cui Canming Wang Guosong Zhang Qiang Song Wenxia Sun Xiaojie Song Mingyuan Sun Jian Tian 《Journal of the American Ceramic Society》2017,100(4):1339-1349
Porous TiO2 films decorated with Bi2O3 nanoparticles are fabricated via alkali‐hydrothermal of titanium (Ti) plate by varying the reaction time. The amorphous TiO2 is transformed into anatase after annealing the films at 500°C in air. The p‐type Bi2O3 nanoparticles are successfully assembled on the surface of porous n‐type TiO2 films through the ultrasonic‐assisted successive ionic layer adsorption and reaction (SILAR) technique to form Bi2O3/TiO2 nanostructure by the two cycles. The obtained Bi2O3/TiO2 films are consisted of a well‐ordered and uniform porous structure with an average pore diameter of about 100‐200 nm containing homogeneously dispersed Bi2O3 nanoparticles of ~5 nm diameter. Moreover, the resultant composites present excellent photocatalytic performance toward methyl blue (MB) degradation under UV and visible light irradiation, which could be mainly ascribed to the enhanced light adsorption capacity of unique composite structure and the formation of p‐n heterojunctions in the porous Bi2O3/TiO2 films. This research is helpful to design and construct the highly efficient heterogeneous semiconductor photocatalysts. 相似文献