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1.
Myongil Kong Shenglin Jiang Tiantian Xie Haibo Zhang 《Microelectronic Engineering》2009,86(11):2320-2323
The sintering process of semiconducting Y-doped BaTiO3 ceramics added with BaB2O4 as low temperature sintering aid were investigated. When the low temperature sintering aid BaB2O4 added Y-doped BaTiO3 ceramics prepared by Sol-Gel method, the sintering temperature of BaTiO3-based ceramics would be greatly decreased, and also widen sintering range. Y-doped BaTiO3 ceramics with BaB2O4 addition can be obtained at 1050 °C. Ceramics samples with room temperature resistivity 60-80 Ω cm, ratio of the maximum resistivity to minimum resistance (Rmax/Rmin) 104 and temperature coefficient of resistivity (α) 10%/°C were obtained. 相似文献
2.
Through improved synthesis process, resistance reduction effect of (K0.5Bi0.5)TiO3 (KBT) doping in Y–Mn co-doped BaTiO3 (BT) lead free ceramics was investigated. By different doping methods (doping K2O, Bi2O3 and TiO2 or synthesized KBT), medium Curie temperature (around 130 °C) lead free BT ceramics were obtained with ultra-low resistivity (13.84 Ωcm) with a temperature maintaining process at 700 °C. In this contribution, effect of sintering process and doping methods is discussed in detail. 相似文献
3.
J. G. Fagan D. A. Partis J. A. Richmond-Hope V. R. W. Amarakoon 《Journal of Electronic Materials》1994,23(11):1103-1109
Grain growth and texturing of YBa2Cu3O7−δ is greatly influenced by the presence of liquid phase additives during sintering. Oxides such as TiO2, SiO2, Bi2O3, and Pr6O11 were incorporated into the liquid phase during the sintering of YBa2Cu3O7−δ (123) by use of grain boundary diffusion couples and the microstructure was analyzed using scanning electron microscopy/electron
dispersive spectroscopy. Exaggerated grain growth and domain formation was observed in bulk specimens. Differential thermal
analysis and real time dynamic x-ray diffraction were used to determine reaction sequencing. The ability and extent of domain
formation was determined for 123 samples coupled with impurity oxides to be a function of sintering temperature (940–980°)
and oxygen partial pressure. Enhanced texturing was observed at low PO2 atmospheres. The addition of Bi2O3 and TiO2 was shown to degrade dc magnetic susceptibility of 123 whereas SiO2 and Pr6O11 enhanced it. The domain formation and texturing takes place in the bulk for 123 at temperatures of 980°C or below (i.e. well
below the peritectic decomposition temperature) by the interaction of an impurity doped liquid phase followed by a precipitation
and exaggerated grain growth. 相似文献
4.
Colin L. Freeman James A. Dawson Hung‐Ru Chen Liubin Ben John H. Harding Finlay D. Morrison Derek C. Sinclair Anthony R. West 《Advanced functional materials》2013,23(31):3925-3928
The energetics of La‐doping in BaTiO3 are reported for both (electronic) donor‐doping with the creation of Ti3+ cations and ionic doping with the creation of Ti vacancies. The experiments (for samples prepared in air) and simulations demonstrate that ionic doping is the preferred mechanism for all concentrations of La‐doping. The apparent disagreement with electrical conduction of these ionic doped samples is explained by subsequent oxygen‐loss, which leads to the creation of Ti3+ cations. Simulations show that oxygen‐loss is much more favorable in the ionic‐doped system than undoped BaTiO3 due to the unique local structure created around the defect site. These findings resolve the so‐called “donor‐doping” anomaly in BaTiO3 and explain the source of semiconductivity in positive temperature coefficient of resistance (PTCR) BaTiO3 thermistors. 相似文献
5.
High‐Rate Continuous Synthesis of Nanocrystalline Perovskites and Metal Oxides in a Colliding Vapor Stream of Microdroplets
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Teyeb Ould‐Ely Lyle Kaplan‐Reinig Daniel E. Morse 《Advanced functional materials》2014,24(9):1275-1282
A high‐rate, continuous synthesis of functional nanomaterials using a home engineered reactor is reported. The reactor is able to produce low‐cost, kilogram‐scale BaTiO3 nanopowders with a nanocrystalline particle size less than 30 nm at mild temperatures (<100 °C) and ambient pressure. Nebulization and collision of warm microdroplets (60–80 °C) of Ba(OH)2 and Ti(O‐nBu)4 very quickly result in total hydrolysis and subsequent conversion to BaTiO3, yielding 1.3 kg/day of high purity, highly crystalline nanoparticles (25–30 nm). This synthesis procedure also enables high‐rate production of TiO2 anatase (2.9 kg/day). It therefore provides a general platform for processing and scaling up of functional inorganic nanomaterials under very mild conditions. 相似文献
6.
Se-Ho Kim 《Microelectronic Engineering》2009,86(1):59-62
Microwave properties of Li-doped (Ba,Sr)TiO3 thick film interdigital capacitors have been investigated. According to the reported papers, BaSrTiO3 materials, paraelectric state at the room temperature, have high dielectric permittivity (>500 @ 1 MHz) and low loss tangent (<0.01 @ 1 MHz) in epitaxial thin film form; however, the sintering temperature of BaSrTiO3 is over 1350 °C. In order to reduce the sintering temperature, Li (3 wt%) was added to the BaSrTiO3 materials, and 10 μm thick Li-doped (Ba,Sr)TiO3 films were screen printed on the alumina (Al2O3) substrate and sintered at 900 °C. Interdigital capacitor patterns with five fingers of 200 μm gap and 250 μm length were also designed and fabricated by employing the screen printing method with Ag electrode. The structural feature was analyzed with X-ray diffraction method. Frequency and temperature-dependent dielectric properties were characterized from 1 kHz to 1 MHz and 303-403 K, respectively. Also, current-voltage characteristics were investigated with an elevated temperature. Microwave transmission and reflectance properties of thick film interdigital capacitors will be discussed, and frequency dispersion of dielectric properties will be presented. Specially, designed Au/Li-doped (Ba,Sr)TiO3/Ag-Pd/Al2O3 vertical structure was prepared to measure the tunability. In this sandwich type structure, Li-doped (Ba,Sr)TiO3 films showed tenability of 7.15% at a bias electric field of 20 kV/cm. 相似文献
7.
New Strategy for Polysulfide Protection Based on Atomic Layer Deposition of TiO2 onto Ferroelectric‐Encapsulated Cathode: Toward Ultrastable Free‐Standing Room Temperature Sodium–Sulfur Batteries
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Dingtao Ma Yongliang Li Jingbo Yang Hongwei Mi Shan Luo Libo Deng Chaoyi Yan Muhammad Rauf Peixin Zhang Xueliang Sun Xiangzhong Ren Jianqing Li Han Zhang 《Advanced functional materials》2018,28(11)
The room temperature (RT) sodium–sulfur batteries (Na–S) hold great promise for practical applications including energy storage and conversion due to high energy density, long lifespan, and low cost, as well based on the abundant reserves of both sodium metal and sulfur. Herein, freestanding (C/S/BaTiO3)@TiO2 (CSB@TiO2) electrode with only ≈3 wt% of BaTiO3 additive and ≈4 nm thickness of amorphous TiO2 atomic layer deposition protective layer is rational designed, and first used for RT Na–S batteries. Results show that such cathode material exhibits high rate capability and excellent durability compared with pure C/S and C/S/BaTiO3 electrodes. Notably, this CSB@TiO2 electrode performs a discharge capacity of 524.8 and 382 mA h g?1 after 1400 cycles at 1 A g?1 and 3000 cycles at 2 A g?1, respectively. Such superior electrochemical performance is mainly attributed from the “BaTiO3‐C‐TiO2” synergetic structure within the matrix, which enables effectively inhibiting the shuttle effect, restraining the volumetric variation and stabilizing the ionic transport interface. 相似文献
8.
《Materials Science in Semiconductor Processing》2002,5(2-3):223-225
One of the perspective directions in using positive temperature coefficient (PTC) thermistors is their application in surface heater in various electronic devices and integrated circuits. The special interest in this connection makes possible fabrication of thin film structures on the basis of materials with PTCR. In the given work a result of the investigation of Y–BaTiO3 thin films has been presented. Thin films have been deposited by RF-sputtering technique. Films had thickness of 1.5–2 μm. Subsequent annealing was carried out to obtain polycrystalline films of a single phase. The temperature dependence of resistance of films has been investigated. The increase of the resistance were observed in the temperature range 50–80°C. The jump of the resistance in field of phase transition was 70%. 相似文献
9.
S.J. Limmer S. Seraji Y. Wu T.P. Chou C. Nguyen G.Z. Cao 《Advanced functional materials》2002,12(1):59-64
The ability to form oxide nanorods is of great interest in a number of areas. In this paper, we report the template‐based growth of nanorods of several oxide ceramics, formed by means of a combination of sol–gel processing and electrophoretic deposition. Both single metal oxides (TiO2, SiO2) and complex oxides (BaTiO3, Sr2Nb2O7, and Pb(Zr0.52Ti0.48)O3) have been grown by this method. Uniformly sized nanorods of about 125–200 nm in diameter and 10 μm in length were grown over large areas with near unidirectional alignment. Desired stoichiometric chemical composition and crystal structure of the oxide nanorods was readily achieved by an appropriate procedure of sol preparation, with a heat treatment (700 °C for 15 min) for crystallization and densification. 相似文献
10.
D. Ehre H. Cohen V. Lyahovitskaya A. Tagantsev I. Lubomirsky 《Advanced functional materials》2007,17(7):1204-1208
A model of structural transformations of amorphous into quasi‐amorphous BaTiO3 is suggested. The model is based on previously published data and on X‐ray photoelectron spectroscopy data presented in the current report. Both amorphous and quasi‐amorphous phases of BaTiO3 are made up of a network of slightly distorted TiO6 octahedra connected in three different ways: by apices (akin to perovskite), edges, and faces. Ba ions in these phases are located in the voids between the octahedra, which is a nonperovskite environment. These data also suggest that Ba ions compensate electrical‐charge imbalance incurred by randomly connected octahedra and, thereby, stabilize the TiO6 network. Upon heating, the edge‐to‐edge and face‐to‐face connections between TiO6 octahedra are severed and then reconnected via apices. Severing the connections between TiO6 octahedra requires a volume increase, suppression of which keeps some of the edge‐to‐edge and face‐to‐face connections intact. Transformation of the amorphous thin films into the quasi‐amorphous phase occurs during pulling through a steep temperature gradient. During this process, the volume increase is inhomogeneous and causes both highly anisotropic strain and a strain gradient. The strain gradient favors breaking those connections, which aligns the distorted TiO6 octahedra along the direction of the gradient. As a result, the structure becomes not only anisotropic and non‐centrosymmetric, but also acquires macroscopic polarization. Other compounds may also form a quasi‐amorphous phase, providing that they satisfy the set of conditions derived from the suggested model. 相似文献
11.
Myung‐Yeon Cho Sunghoon Kim Ik‐Soo Kim Eun‐Seong Kim Zhi‐Ji Wang Nam‐Young Kim Sang‐Wook Kim Jong‐Min Oh 《Advanced functional materials》2020,30(3)
A new capacitive‐type humidity sensor is proposed using novel materials and fabrication process for practical applications in sensitive environments and cost‐effective functional devices that require ultrasensing performances. Metal halide perovskites (CsPbBr3 and CsPb2Br5) combined with diverse ceramics (Al2O3, TiO2, and BaTiO3) are selected as sensing materials for the first time, and nanocomposite powders are deposited by aerosol deposition (AD) process. A state‐of‐the‐art CsPb2Br5/BaTiO3 nanocomposite humidity sensor prepared by AD process exhibits a significant increase in humidity sensing compared with CsPbBr3/Al2O3 and CsPbBr3/TiO2 sensors. An outstanding humidity sensitivity (21426 pF RH%?1) with superior linearity (0.991), fast response/recovery time (5 s), low hysteresis of 1.7%, and excellent stability in a wide range of relative humidity is obtained owing to a highly porous structure, effective charge separation, and water‐resistant characteristics of CsPb2Br5. Notably, this unprecedented result is obtained via a simple one‐step AD process within a few minutes at room temperature without any auxiliary treatment. The synergetic combination of AD technique and perovskite‐based nanocomposite can be potentially applied toward the development of multifunctional sensing devices. 相似文献
12.
Si-doped barium titanate nanopowders and ceramics were prepared through the sol-gel process. The powders and ceramics were characterized by methods of XRD, SEM and TEM. The dielectric properties of the ceramics were also determined. The results indicated that the powders were nanopowders and they were all cubic BaTiO3 phase with the concentration of Si ?5.0 mol%. When the concentration of Si increased to 10.0 mol%, another phase of Ba2TiSi2O8 appeared. After sintering, the cubic BaTiO3 phase was transformed into tetrahedron BaTiO3 phase. Si doping with low concentration resulted in improving grain growth and reduced dielectric loss. As the sintering temperature increased, the dielectric properties of the ceramics decreased. BaTiO3 ceramics doped with Si all had a small peak at room temperature in ε−T cures. Specially, the ceramic doped with 0.3 mol% Si had evident double peaks, the maximum room temperature permittivity (4081) and the minimum dielectric loss (0.004). 相似文献
13.
《Solid-state electronics》1987,30(9):947-951
The anodic oxidation of the silicides CoSi, CoSi2, CrSi2, Ni2Si, NiSi, NiSi2, Pd2Si, PtSi, TiSi2 and ZrSi2 was studied by using Rutherford backscattering of 2MeV alpha particles. The room temperature oxidation was carried out at a constant current density of 8.9 mA cm−2 using n-methylacetamide (2% H20 and 1% KNO3) as electrolyte. No oxidation of Pd2Si and PtSi was detected. Pure SiO2 layers were grown on CoSi, CoSi2, Ni2Si, NiSi and NiSi2 at a much lower rate than on Si〈100〉 and with a thickness increase per volt of 0.6 ± 0.03 nm V−1. Mixed layers of SiO2/metal oxide were grown on CrSi2, TiSi2 and CrSi2. All oxidations occurred at the expense of the silicide layer. It is also shown how the purity of the SiO2 layer formed can be predicted from thermodynamic considerations. 相似文献
14.
Surfaces and interfaces of ferroelectric oxides exhibit enhanced functionality, and therefore serve as a platform for novel nano and quantum technologies. Experimental and theoretical challenges associated with examining the subtle electro‐chemo‐mechanical balance at metal‐oxide surfaces have hindered the understanding and control of their structure and behavior. Here, combined are advanced electron‐microscopy and first‐principles thermodynamics methods to reveal the atomic‐scale chemical and crystallographic structure of the surface of the seminal ferroelectric BaTiO3. It is shown that the surface is composed of a native <2 nm thick TiOx rock‐salt layer in epitaxial registry with the BaTiO3. Using electron‐beam irradiation, artificial TiOx sites with sub‐nanometer resolution are successfully patterned, by inducing Ba escape. Therefore, this work offers electro‐chemo‐mechanical insights into ferroelectric surface behavior in addition to a method for scalable high‐resolution beam‐induced chemical lithography for selectively driving surface phase transitions, and thereby functionalizing metal‐oxide surfaces. 相似文献
15.
J. F. Peng X. J. Zheng Y. Q. Gong K. Zhan Z. H. Dai 《Journal of Electronic Materials》2014,43(3):724-731
0.94(Na0.5Bi0.5)TiO3–0.06BaTiO3 (NBT–BT6) ferroelectric thin films have been fabricated on Pt–Ti–SiO2–Si(100) substrate by metal–organic decomposition. The effects of annealing temperature (650–800°C) on the microstructure, and the piezoelectric, ferroelectric, and dielectric properties of the thin films were studied in detail. The residual stress was evaluated by the orientation average method to clarify its dependence on annealing temperature and grain size, and it was correlated with the electric properties to understand the mechanism of piezoelectric enhancement. Among the thin films, NBT–BT6 thin film annealed at 750°C has the largest effective piezoelectric coefficient, 95.1 pm/V, remnant polarization, 49.7 μC/cm2, spontaneous polarization, 105.2 μC/cm2, and dielectric constant, 504, and the lowest dielectric loss, 0.05, and tensile residual stress, 24.5 MPa. For the NBT–BT6 thin film annealed at 750°C, a wide temperature range, 183–210°C, around the phase transition temperature (T m) was observed in the dielectric temperature plots, and the diffusion coefficients (γ) were quantitatively assessed as 1.6, 1.78, and 1.6. Piezoelectric performance is discussed on the basis of the dispersion phase transition and residual stress. 相似文献
16.
The piezoelectric nanocrystalline ceramics of (Bi0.5Na0.5) TiO3, 0.94(Bi0.5Na0.5) TiO3–0.06BaTiO3, 0.82(Bi0.5Na0.5) TiO3–0.18(Bi0.5K0.5) TiO3 and 0.85(Bi0.5Na0.5) TiO3–0.144(Bi0.5K0.5)TiO3–0.006BaTiO3 (abbreviated as BNT, BNBT6, BNKT18 and BNT–BT–BKT, respectively) have been synthesized by a modified solid state approach using high-energy planetary ball-milling. The crystal structures of ceramics were determined using X-ray diffraction (XRD) method and that the microstructures as well as the morphology of the sintered ceramic specimens were observed using scanning-electron microscopy (SEM). The dielectric coefficient was also calculated based on its relation with a constant capacitance measured by an electrical circuit on the basis of the Wetston–Bridge and the piezoelectric coefficient (d33) measured with a d33-meter. On the calcination of powders the XRD results showed that the perovskite phase was formed perfectly and the crystallite sizes of BNT, BNBT6, BNKT18 and BNT–BT–BKT were estimated at about >100, 55, 36 and 63 nm, respectively. Also, the crystallite sizes of the calcinated BNT powders over the course of 5, 10, 20, 30 and 40 h of ball-milling were estimated at about 86, 82, 72, 53, 81 nm, respectively. Moreover, the results of XRD and SEM analysis of the sintered powders at 750–1150 °C confirmed the positive effect of nanocrystalline formation during ball-milling in decreasing the sintering temperature and increasing the density of the sintered samples. Furthermore, electrical calculations such as dielectric and piezoelectric coefficients showed that the modified BNKT18 nanocrystalline ceramic sintered at 1150 °C was to have the best values of dielectric (εr=792 at 1 kHz) and piezoelectric coefficients (d33=85.9 pC/N) in comparison with the other synthesized piezoelectric ceramics. 相似文献
17.
《Materials Science in Semiconductor Processing》2012,15(1):47-51
The effect of varying sintering temperature in the range 1270–1430 °C on the resistivity–temperature characteristics of semiconducting BaTiO3 based positive temperature coefficient of resistance thermistors containing a donor-dopant, but without acceptor doping, was investigated by impedance spectroscopy. As the sintering temperature was increased the specimen resistivity around the Curie temperature decreased, while the peak resistivity, obtained above the Curie temperature, remained approximately constant. The change in PTC behaviour with increasing sintering temperature is inconsistent with the standard double Schottky barrier model, but is explained in terms of grain size variations coupled with a, sintering temperature independent, grain boundary barrier layer thickness of 0.50±0.04 μm. 相似文献
18.
A large jump of proton transfer rates across solid‐to‐solid interfaces by inserting an ultrathin amorphous silica layer into stacked metal oxide nanolayers is discovered using electrochemical impedance spectroscopy and Fourier‐transform infrared reflection absorption spectroscopy (FT‐IRRAS). The triple stacked nanolayers of Co3O4, SiO2, and TiO2 prepared by atomic layer deposition (ALD) enable a proton flux of 2400 ± 60 s?1 nm?2 (pH 4, room temperature), while a single TiO2 (5 nm) layer exhibits a threefold lower flux of 830 s?1 nm?2. Based on FT‐IRRAS measurements, this remarkable enhancement is proposed to originate from the sandwiched silica layer forming interfacial SiOTi and SiOCo linkages to TiO2 and Co3O4 nanolayers, respectively, with the O bridges providing fast H+ hopping pathways across the solid‐to‐solid interfaces. Together with the complete O2 impermeability of a 2 nm ALD‐grown SiO2 layer, the high flux for proton transport across multi‐stack metal oxide layers opens up the integration of incompatible catalytic environments to form functional nanoscale assemblies such as artificial photosystems for CO2 reduction by H2O. 相似文献
19.
M.T. Benlahrache S.E. Barama N. Benhamla S. Achour 《Materials Science in Semiconductor Processing》2006,9(6):1115
The titanate of barium (BaTiO3) is a ferroelectric material with perovskite structure. The electric properties (ferroelectricity, positive temperature coefficient, piezoelectricity, etc.) of BaTiO3 were largely studied. Usually, addition of small quantities of impurity can modify the dielectric properties of BaTiO3 and widen its number of applications. In this investigation different additions of sodium niobate (NaNbO3), according to the composition, (1−x) BaTiO3+x NaNbO3 with x=1, 3, 5, 7 and 10 mol%, were considered. Additionally, the effect of simultaneous addition of 3 mol% NaNbO3 and 3 mol% SiO2 on the dielectric properties we studied as function of temperature, frequency and the applied bias. The obtained results reveal a net evolution of permittivity with addition. Furthermore, the obtained results show that the permittivity is independent of the applied electric field at temperature lower than Curie point (Tc), but presents relatively high values at low frequencies. Beyond this temperature, the permittivity considerably increases (about 25×103) and largely depends both on frequency and applied voltage. 相似文献
20.
Se-Ho Kim 《Microelectronic Engineering》2010,87(1):79-10160
The crystalline and electrical properties of Li doped 0.7(Ba,Sr)TiO3-0.3MgO thick film interdigital capacitors have been investigated. Screen printing method was employed to fabricate Li doped 0.7(Ba,Sr)TiO3-0.3MgO thick films on the alumina substrates. (Ba,Sr)TiO3 materials have high dielectric permittivity (>500 @ 1 MHz) and low loss tangent (0.01 @ 1 MHz) in the epitaxial thin film form. To improve dielectric properties and reduce sintering temperature, MgO and Li were added, respectively. 10 μm thick films were screen printed on the alumina substrates and then interdigital capacitors with seven fingers of 200 μm finger gap were patterned with Ag electrode. Current-voltage characteristics were analyzed with elevated temperature range. Up to 50 °C, the thick films showed positive temperature coefficient of resistivity (dρ/dT) of 6.11 × 108 Ω cm/°C, then film showed negative temperature coefficient of resistivity (dρ/dT) of −1.74 × 108 Ω cm/°C. From the microwave measurement, the relative dielectric permittivity of Li doped 0.7(Ba,Sr)TiO3-0.3MgO thick films interdigital capacitors were between 313 at 1 GHz and 265 at 7 GHz. 相似文献