共查询到20条相似文献,搜索用时 15 毫秒
1.
《Ceramics International》2016,42(5):6273-6281
This work deals with some physical investigation on SnO2–ZnSnO3 ceramics grown on glass substrates at different temperatures (450 °C and 500 °C). Structural and optical properties were investigated using X-Ray diffraction (XRD), Raman, infrared (IR) absorption (FTIR), UV–visible spectroscopy and Photoluminescence (PL) techniques. XRD results revealed the existence of a mixture of SnO2/ZnSnO3 phases at different annealing temperatures. Structural analysis showed that both phases are polycrystalline. On the other hand, the optical constants (refractive index, extinction coefficient and the dielectric constants) have been obtained by the transmittance and the reflectance data. The optical band gap energy changed from 3.85 eV to 3.68 eV as substrate temperature increased from 450 °C to 500 °C. Raman, FTIR modes and PL reinforced this finding regarding the existence of biphasic (SnO2 and ZnSnO3) which is detected also by X-Ray diffraction analysis. Finally, the Lattice Compatibility Theory was evoked for explaining the unexpected incorporation of zinc ions in a rhombohedral structure within SnO3 trigonal lattice, rather than the occupation of SnO2 available free loci. All the results have been discussed in terms of annealing temperature. 相似文献
2.
Ch. Sujatha K. Venugopal Reddy K. Sowri Babu A. RamaChandra Reddy K.H. Rao 《Ceramics International》2012,38(7):5813-5820
Mg0.5Cu0.05Zn0.45Fe2O4 nanoparticles were prepared through sol–gel method using polyvinyl alcohol as a chelating agent. The as prepared sample was annealed at three different temperatures (500 °C, 700 °C and 900 °C). The phase formation, morphology and magnetic properties with respect to annealing temperature were studied using the characterisation techniques like X-ray diffraction (XRD) as well as Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM), respectively. The crystallite size and magnetisation showed increasing trend with annealing temperature. The coercivity increased up to a particular annealing temperature and decreased thereafter, indicating transition from single domain to multi domain state with increasing annealing temperature. Further, to know the suitability of the material, as a ferrite core, in multilayer chip inductors, the powder sample annealed at 500 °C was compacted in the form of torroids and sintered at three different temperatures (800 °C, 900 °C and 950 °C). The permeability showed increasing trend with the increase of sintering temperature since the permeability depends on microstructure. The frequency dispersion of permeability, for the sintered samples, demonstrated high frequency stability as well as high operating frequency. The cut-off frequency for the sintered samples 800 °C, 900 °C and 950 °C is 32 MHz, 30.8 MHz and 30.4 MHz, respectively. 相似文献
3.
In this study, TiO2-PVP nanofibers were successfully synthesized on an aluminium collector by using cost-effective electrospinning technique. The nanofibers were prepared at different polymer concentrations, needle diameters and annealing temperatures and properties were studied by various characterizations. The structural properties were studied by X-ray diffraction (XRD) and Raman spectroscopy techniques. Surface morphology and elemental analysis of the samples were investigated by scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS). The optical properties were carried out by UV–Visible absorption spectroscopy (UV–Vis). By varying the polymer concentration and needle diameter, the effect of viscosity and surface tension on the formation of TiO2-PVP nanofibers was clearly observed by SEM micro images. EDS spectrum shows effective composition of pure TiO2 nanofibers. XRD peaks observed at temperatures 500 °C, 700 °C and 900 °C confirmed the anatase, mixed and rutile phases of TiO2 nanofibers respectively. Raman studies also confirmed these phases of TiO2 nanofibers. The optical band-gap values calculated using Kubelka-Munk function lies in the range of 3.02–3.22 eV. 相似文献
4.
Rongfeng Zhu Bijun Fang Xiangyong Zhao Shuai Zhang Dun Wu Jianning Ding 《Journal of the European Ceramic Society》2018,38(4):1463-1472
The high-Curie temperature (TC) 0.15Pb(Mg1/3Nb2/3)O3-0.38PbHfO3-0.47PbTiO3 (PMN-PH-PT) piezoelectric ceramics were prepared by the partial oxalate route via the B-site oxide mixing method. The obtained uniform nm-sized PMN-PH-PT precursor powders provide high calcining and sintering activity for synthesizing ceramics, based on which the synthesis conditions were tailored as calcining at 775 °C and sintering at 1245 °C. The partial oxalate route synthesized PMN-PH-PT ceramics are far superior to the counterparts synthesized by the columbite precursor method and exhibit excellent thermal stability of the piezoelectric properties under TC (~292 °C), ensuring the potential application in transducers under elevated environmental temperatures. The temperature dependent Raman spectroscopy not only proves the occurrence of the ferroelectric to paraelectric phase transition around TC, but also confirms the successive phase symmetry transitions, which correlate with the polar nanoregions (PNRs) and/or the coexistence of multiple ferroelectric phases, revealing the origin of the enhanced electrical properties in the PMN-PH-PT ceramics. 相似文献
5.
Yu-Kwang Seo Jung-Hye Eom Young-Wook Kim 《Journal of the European Ceramic Society》2018,38(2):445-452
Process-tolerant SiC ceramics were prepared by pressureless sintering at 1850–1950 °C for 2 h in an argon atmosphere with a new quaternary additive (Al2O3-Y2O3-CaO-SrO). The SiC ceramics can be sintered to a > 94% theoretical density at 1800–1950 °C by pressureless sintering. Toughened microstructures consisting of relatively large platelet grains and small equiaxed grains were obtained when SiC ceramics were sintered at 1850–1950 °C. The presently fabricated SiC ceramics showed little variability of the microstructure and mechanical properties with sintering within the temperature range of 1850–1950 °C, demonstrating process-tolerant behavior. The thermal conductivity of the SiC ceramics increased with increasing sintering temperature from 1800 °C to 1900 °C due to decreases of the lattice oxygen content of the SiC grains and residual porosity. The flexural strength, fracture toughness, and thermal conductivity of the SiC ceramics sintered at 1850–1950 °C were in the ranges of 444–457 MPa, 4.9–5.0 MPa m1/2, and 76–82 Wm?1 K?1, respectively. 相似文献
6.
Jianbo Yu Zhigang Yang Zongcheng Song Kang Deng Zhongming Ren 《Ceramics International》2018,44(6):5915-5920
Porous Al2O3-based ceramics were successfully fabricated using ball-shaped powders by preceramic polymer process in N2 atmosphere. These results showed that the amorphous Si-O-C ceramics were formed on the surface of ball-shaped Al2O3 particles by the pyrolysis of the silicone resin during sintering in N2 atmosphere, which played a role in connecting the Al2O3 particles by forming the sintering necks. When the sintering temperatures increased from 1100 °C to 1600 °C, the formed Si-O-C ceramics still existed in the amorphous state and had no crystallization. Interestingly, the amorphous β-SiC formed at 1300 °C and its amount gradually increased with further increasing temperatures. The linear shrinkage rate of the samples varied from 0.49% to 0.73% and the weight loss rate increased from 2.01% to 10.77%. The apparent porosity remarkably varied with the range of 24.9% and 34.5%, as the bulk-density varied from 2.66 to 2.47 g/cm3. The bending strength gradually increased from 9.36 to 22.51 MPa with increasing temperatures from 1100 °C to 1500 °C, however, the bending strength remarkably decreased at 1600 °C, which was attributed to the comprehensive function of the high porosity, broken Al2O3 particles and weak connection between Al2O3 particles in the samples. 相似文献
7.
J. Suchanicz A. Kania P. Czaja A. Budziak A. Niewiadomski 《Journal of the European Ceramic Society》2018,38(2):567-574
Dense K0.5Bi0.5TiO3 (KBT) lead-free ceramics were prepared by conventional solid reaction route. Their temperature behavior (up to 600 °C) was investigated by X-ray diffraction, DSC, dielectric spectroscopy and electric field-polarization technique. The first temperature dependent Raman scattering studies were also performed. X-ray and Raman scattering results show that samples exhibit a single perovskite structure with cubic symmetry at temperatures higher than approximately 400 °C and with coexistence of the cubic and tetragonal phases below this temperature. Two structural phase transitions between tetragonal phases in temperature range 200–225 °C and between tetragonal and cubic ones near 400 °C are observed. The content of the tetragonal phase increases with decreasing temperature and at room temperature it reaches more than 70%. Temperature- dependent P-E loops and pyroelectric data revealed a polar behavior in KBT up to about 400 °C, which means that the intermediate phase (~270–380 °C) is rather ferroelectric than antiferroelectric. 相似文献
8.
《Journal of the European Ceramic Society》2006,26(10-11):1831-1834
Effects of slow-cooling at high temperatures and annealing at intermediate temperatures on dielectric loss tangent of AlN ceramics were explored. Y2O3 was added as a sintering additive to AlN powders, and the powders were pressureless-sintered at 1900 °C for 2 h in a nitrogen flow atmosphere. In succession to the sintering, AlN samples were slow-cooled at a rate of 1 °C/min from 1900 to 1750 °C and/or annealed at 970 °C for 4 h. Al5Y3O12 was detected in the AlN ceramics obtained by the slow-cooling and AlYO3 was found in the ceramics cooled at a rate of 30 °C/min. AlN ceramics with a relative density of 0.986 were obtained by the slow-cooling method. On the other hand, very low tan δ values between 2.6 and 4.6 × 10−4 were obtained when the AlN ceramics were annealed at 970 °C for 4 h. 相似文献
9.
Nikola Kanas Sathya Prakash Singh Magnus Rotan Mohsin Saleemi Michael Bittner Armin Feldhoff Truls Norby Kjell Wiik Tor Grande Mari-Ann Einarsrud 《Journal of the European Ceramic Society》2018,38(4):1592-1599
Due to high figure of merit, Ca3Co4 ? xO9 + δ (CCO) has potential as p-type material for high-temperature thermoelectrics. Here, the influence of processing including solid state sintering, spark plasma sintering and post-calcination on stability, microstructure and thermoelectric properties is reported. By a new post-calcination approach, single-phase materials were obtained from precursors to final dense ceramics in one step. The highest zT of 0.11 was recorded at 800 °C for CCO with 98 and 72% relative densities. In situ high-temperature X-ray diffraction in air and oxygen revealed a higher stability of CCO in oxygen (~970 °C) than in air (~930 °C), with formation of Ca3Co2O6 which also showed high stability in oxygen, even at 1125 °C. Since achievement of phase pure high density CCO by post-calcination method in air is challenging, the phase stability of CCO in oxygen is important for understanding and further improvement of the method. 相似文献
10.
Seshendra Reddy Ch Liwen Zhang Tuo Kang Yangsen Lin Yejun Qiu Sivasankar Reddy A 《Ceramics International》2018,44(5):4586-4591
Tin oxide (SnO2) nanofibers were fabricated by electrospinning technique and subsequent annealed at different temperatures. The structure, morphology and optical properties of the annealed samples were characterized by X-ray diffraction (XRD), Raman, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR),and optical absorption techniques. The phase of SnO2 of all samples is rutile (tetragonal), and at higher annealing temperatures, good crystallinity and lower absorption were obtained. Annealing of the samples at 600 °C caused the lower absorption and higher optical band gap, and the decrease of the absorption was probably because the fiber structure changed from solid to hollow structure. From PL spectra, it was observed that the SnO2 hollow nanofibers annealed at 600 °C revealed green emission at 530 nm. 相似文献
11.
《Ceramics International》2016,42(5):6136-6144
In the present work, α-Fe2O3 nanoparticles were successfully synthesized by Pechini sol–gel (PSG) method following annealing at 550 °C. The morphology and microstructure of the prepared α-Fe2O3 nanoparticles were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman analysis. The electrical and sensing properties were also investigated. The α-Fe2O3 based sensor showed good sensitivity and selectivity towards ethanol at the optimal temperature of 225 °C. Moreover, the sensor displayed good electrical and sensing stability. These results suggest the potential applications of α-Fe2O3 synthesized by Pechini sol–gel method as a sensor material for ethanol detection. 相似文献
12.
Li-Li Wang Lin Mei Guang-Hua Liu Gang He Jiang-Tao Li Li-Hua Xu 《Ceramics International》2013,39(1):233-238
Bulk glasses containing HfO2 nano-crystallites of 20–50 nm were prepared by hot-pressing of HfO2–Al2O3–Y2O3 glass microspheres at 915 °C for 10 min. By annealing at temperatures below 1200 °C, the bulk glasses were converted into transparent glass-ceramics with HfO2 nano-crystallites of 100–200 nm, which showed the maximum transmittance of ~70% in the infrared region. An increase of annealing temperature (>1300 °C) resulted in opaque YAG/HfO2/Al2O3 eutectic ceramics. The eutectic ceramics contained fine Al2O3 crystallites and showed a high hardness of 19.8 GPa. The fracture toughness of the eutectic ceramics increased with increasing annealing temperature, and reached the maximum of 4.0 MPa m1/2. 相似文献
13.
Anis H. Fakeeha Ahmed S. Al-Fatesh Biswajit Chowdhury Ahmed A. Ibrahim Wasim U. Khan Shahid Hassan Kasim Sasudeen Ahmed Elhag Abasaeed 《中国化学工程学报》2018,26(9):1904-1911
Methane decomposition reaction has been studied at three different activation temperatures (500 °C, 800 °C and 950 °C) over mesoporous alumina supported Ni–Fe and Mn–Fe based bimetallic catalysts. On co-impregnation of Ni on Fe/Al2O3 the activity of the catalyst was retained even at the high activation temperature at 950 °C and up to 180 min. The Ni promotion enhanced the reducibility of Fe/Al2O3 oxides showing higher catalytic activity with a hydrogen yield of 69%. The reactivity of bimetallic Mn and Fe over Al2O3 catalyst decreased at 800 °C and 950 °C activation temperatures. Regeneration studies revealed that the catalyst could be effectively recycled up to 9 times. The addition of O2 (1 ml, 2 ml, 4 ml) in the feed enhanced substantially CH4 conversion, the yield of hydrogen and the stability of the catalyst. 相似文献
14.
Li2CO3 has been used as a sintering aid for fabricating lead-free ferroelectric ceramic 0.93(Bi0.5Na0.5TiO3)-0.07BaTiO3. A small amount (0.5 wt%) of it can effectively lower the sintering temperature of the ceramic from 1200 °C to 980 °C. Unlike other low temperature-sintered ferroelectric ceramics, the ceramic retains its good dielectric and piezoelectric properties, giving a high dielectric constant (1570), low dielectric loss (4.8%) and large piezoelectric coefficient (180 pC/N). The “depolarization” temperature is also increased to 100 °C and the thermal stability of piezoelectricity is improved. Our results reveal that oxygen vacancies generated from the diffusion of the sintering aid into the lattices are crucial for realizing the low temperature sintering. Owing to the low sintering temperature and good dielectric and piezoelectric properties, the ceramics, especially of multilayered structure, should have great potential for practical applications. 相似文献
15.
I.V. Ciuchi C.C. Chung C.M. Fancher C. Capiani J.L. Jones L. Mitoseriu C. Galassi 《Journal of the European Ceramic Society》2018,38(4):1479-1487
Pb0.97La0.03(Zr0.9Ti0.1)0.9925O3 (PLZT 3/90/10) ceramics prepared by solid-state reaction with the compositions near the antiferroelectric/ferroelectric (FE/AFE) phase boundary were studied. From the polarization–electric field P(E) dependence and ex situ X-ray study, an irreversible electric field induced AFE-to-FE phase transition is verified at room temperature. Dielectric and in situ temperature dependent X-ray analysis evidence that the phase transition sequence in PLZT 3/90/10-based ceramics can be readily altered by poling. A first order antiferroelectric-paraelectric (AFE-to-PE) transition occurred at?~190 °C in virgin sample and at?~180 °C in poled sample. In addition, a FE-to-AFE transition occurs in the poled ceramic at much lower temperatures (~120 °C) with respect to the Curie range (~190 °C). The temperature-induced FE-to-AFE transition is diffuse and takes place in a broad temperature range of 72–135 °C. The recovery of AFE is accompanied by an enhancement in the piezoelectric properties. 相似文献
16.
Qi Wang Mei Yang Jiusan Xiao Shuqiang Jiao Hongmin Zhu 《Journal of the European Ceramic Society》2018,38(4):1219-1226
Si-C-N nano-powders with tunable carbon content were synthesized through the reduction of silicon tetrachloride (SiCl4) and trichloromethylsilane (SiCl3CH3) solution by sodium in liquid ammonia. The nano-powders contain two domains of structure, Si-C-N amorphous or continuous random networks (CRNs), and free carbon. The carbon content in Si3+nCnN4 CRNs, is tunable from n = 0 to n = 1. Free carbon will appeared with the increase of the C/Si mole ratio when C/Si is higher than 1/4. The crystallization of amorphous Si-C-N powders occurs at temperatures ranging from 1300 °C to 1500 °C depending on the carbon content. The additive-free dense Si-C-N ceramics with relatively low porosity were fabricated by Spark Plasma Sintering (SPS). 相似文献
17.
《Journal of the European Ceramic Society》2017,37(4):1563-1576
This paper presents the mechanical behavior of LaCoO3 and La0.8Ca0.2CoO3 ceramics under four-point bending in which the two cobaltites are subjected to a low stress of ∼8 MPa at temperatures ranging from room temperature to 1000 °C. Unexpected stiffening is observed in pure LaCoO3 in the 700–900 °C temperature range, leading to a significant increase in the measured Young’s modulus, whereas La0.8Ca0.2CoO3 exhibits softening from 100 °C to 1000 °C, as expected for most materials upon heating. Neutron diffraction, X-ray diffraction and micro-Raman spectroscopy are used to study the crystal structure of the two materials in the RT–1000 °C temperature range. Despite a detailed study, there is no conclusive evidence to explain the stiffening behavior observed in pure LaCoO3 as opposed to the softening behavior in La0.8Ca0.2CoO3 at high temperatures (above 500 °C). 相似文献
18.
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
19.
Francielly Roussenq Cesconeto Mario Borlaf Maria Isabel Nieto Antonio Pedro Novaes de Oliveira Rodrigo Moreno 《Ceramics International》2018,44(1):301-309
CaTiO3 and CaTiO3/TiO2 nanocompounds have been synthesized through a colloidal sol-gel route using Ca2+/TiO2 nanoparticulate sols. The peptization time was determined so that as higher is the Ca2+ concentration, shorter is the peptization time. The obtained cryogels from the respective sols were calcined at different temperatures (300–900 °C) and the structural and morphological changes were characterized mainly by X-ray diffraction and transmission electron microscopy. In all cases, the formation of the CaTiO3 phase was observed after calcination at temperatures as low as 500 °C. Mesoporous cryogels with nanoparticles with sizes below 50 nm were obtained and their photocatalytic activity changes as a function of the calcination temperature and the applied wavelength were determined. Quantum yield values revealed that either CaTiO3 or the CaTiO3/TiO2 (0.4 M ratio) compound can be chosen as the most efficient photocatalyst at higher calcination temperatures and longer wavelengths, while TiO2 is more effective at low calcination temperatures and shorter wavelengths. 相似文献
20.
《Journal of the European Ceramic Society》2005,25(6):927-933
The fracture strength, fracture toughness and apparent Young’s modulus of LaFeO3 ceramics in the temperature region 25–800 °C are reported. The fracture strength of the material was observed to increase from 202 ± 18 MPa at room temperature to 235 ± 38 MPa at 800 °C. The room temperature fracture toughness was 2.5 ± 0.1 MPa m1/2. The fracture toughness decreased to 2.1 ± 0.1 MPa m1/2 at 600 °C, followed by an increase to 3.1 ± 0.3 MPa m1/2 at 800 °C. The temperature dependence of the fracture toughness correlates well with the crystallographic strain, |(a−c)|/(a+c), and ferroelastic toughening of LaFeO3 materials is inferred. Non-elastic stress–strain behaviour of the LaFeO3 materials due to ferroelasticity was confirmed by cyclic compression experiments, and residual strain was observed in the material after unloading. 相似文献