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1.
We present in this paper the experimental results of photoluminescence spectra of Ba0.5Sr0.5TiO3 ceramics. An emission band centered at about 920 nm has been observed at room temperature. When we change the amount of oxygen vacancies in these samples by thermal treatment, these samples show an enhancement of luminescence. Our experimental results indicate that the origin of the photoluminescence is related to the oxygen vacancies in these samples. 相似文献
2.
TiO2 doped WO3 thin films were deposited onto glass substrates and fluorine doped tin oxide (FTO) coated conducting glass substrates, maintained at 500 °C by pyrolytic decomposition of adequate precursor solution. Equimolar ammonium tungstate ((NH4)2WO4) and titanyl acetyl acetonate (TiAcAc) solutions were mixed together at pH 9 in volume proportions and used as a precursor solution for the deposition of TiO2 doped WO3 thin films. Doping concentrations were varied between 4 and 38%. The effect of TiO2 doping concentration on structural, electrical and optical properties of TiO2 doped WO3 thin films were studied. Values of room temperature electrical resistivity, thermoelectric power and band gap energy (Eg) were estimated. The films with 38% TiO2 doping in WO3 exhibited lowest resistivity, n-type electrical conductivity and improved electrochromic performance among all the samples. The values of thermoelectric power (TEP) were in the range of 23-56 μV/K and the direct band gap energy varied between 2.72 and 2.86 eV. 相似文献
3.
SiHua Ouyang ChunChang Wang GuoZhen Liu Meng He KuiJuan Jin ZhiMin Dang HuiBin Lü 《中国科学G辑(英文版)》2008,51(3):232-236
We report here studies on the influence of oxygen pressure on the electroresistance behavior of La0.9Sr0.1MnO3 thin films fabricated by laser molecular beam epitaxy. It was found that the film deposited at lower oxygen pressure shows
larger c-axis parameter, higher resistance, and more distinct electroresistance. These results reveal that the electroresistance of
manganite thin films can be tuned by the conditions of film fabrication.
Supported by the National Natural Science Foundation of China (Grant No. 10334070) and the National Key Basic Research Program
of China (Grant No. 2004CB619004) 相似文献
4.
Jingyang WangTianjin Zhang Ruikun PanZhijun Ma Jinzhao Wang 《Physica B: Condensed Matter》2012,407(1):160-164
Ho3+ doped Ba0.65Sr0.35TiO3 (BST) nanocrystals was prepared by sol-gel method. The structural and morphological properties of the nanocrystals were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The absorption spectrum, photoluminescence spectrum and fluorescence time decay curve were measured at room temperature. Based on the Judd-Ofelt (J-O) theory, the J-O intensity parameters Ωt (t=2, 4, 6) of Ho3+ doped BST nanocrystals were calculated to be 0.67×10−20 cm2, 1.11×10−20 cm2 and 1.09×10−20 cm2, respectively. The emission probabilities, radiative lifetimes and branching ratios of the different Ho3+ transitions were also determined. The emission cross sections of the important intermanifold transitions 5F4,5S2→5I8, 5F5→5I8 and 5F4→5I7 have been calculated from the luminescence spectrum. The room temperature fluorescence lifetime of the 5S2→5I8 transition for Ho3+ in BST nanocrystals was measured and the radiative quantum efficiency was estimated to be 61.9%. 相似文献
5.
利用传统固相反应方法, 分别在1440℃, 1460℃, 1480℃和1500℃烧结条件下, 制备了钙钛矿结构的La0.1Sr0.9TiO3陶瓷样品. 样品的粉末X射线衍射结果显示, 不同烧结温度的La0.1Sr0.9TiO3 陶瓷样品均为单相的正交结构. 从样品的扫描电子显微照片来看, 随着烧结温度的增加, 平均晶粒尺寸逐渐增大. 在室温至800℃的测试温区, 测试了样品的电阻率和Seebeck系数, 系统地研究了不同烧结温度对样品热电性能的影响. 结果表明, 样品的电阻率在测试温区内随着测试温度的升高先略微降低, 然后逐渐升高;总体来看, 样品的电阻率随烧结温度的升高先增大后降低. 在测试温区内, Seebeck系数均为负值, 表明样品的载流子为电子; 随着测试温度的升高, Seebeck系数绝对值均有所增大;随烧结温度升高, Seebeck系数绝对值逐渐增大后显著降低. 1480℃制备的样品因其相对较低的电阻率和相对较高的Seebeck系数绝对值, 在165℃时得到最大的功率因子21 μW·K-2·cm-1. 相似文献
6.
分别采用sol-gel法和磁控溅射法在Si(001)单晶衬底上制备出(111)和(001)取向的MgO缓冲层薄膜,随后在其上生长Ba0.7Sr0.3TiO3(BST30)铁电薄膜.通过X射线衍射,扫描电子显微镜,原子力显微镜等方法研究了薄膜的微结构.实验结果发现,在较厚的MgO(001)缓冲层上可长出(101)取向的BST30薄膜,而在较薄的MgO(111) 缓冲层上则表现出(101)和(111)取向相互竞争的现象,随着MgO(111)缓冲
关键词:
0.7Sr0.3TiO3')" href="#">Ba0.7Sr0.3TiO3
铁电薄膜
择优取向
sol-gel 相似文献
7.
Ba0.5Sr0.5TiO3 (BST) thin films were deposited on copper foils via sol-gel method with La2O3 as a buffer layer. The films were processed in almost inert atmosphere so that the substrate oxidation was avoided while allowing the perovskite film phase to crystallize. The existence of a La2O3 buffer layer between the BST thin film and Cu foil improved the dielectric constant and reduced the leakage current density of the BST thin film. Meanwhile, the BST thin film exhibited ferroelectric character at room temperature, which was contrast to the para-electric behavior of the film without the buffer layer. Effects of La2O3 buffer layer on the crystallizability and microstructure of BST thin films were also investigated. 相似文献
8.
晶粒尺寸对Ba$lt;sub$gt;0.70$lt;/sub$gt;Sr$lt;sub$gt;0.30$lt;/sub$gt;TiO$lt;sub$gt;3$lt;/sub$gt;陶瓷介电性能的影响规律及机理研究
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通过制备晶粒尺寸处于0.1—10 μm之间的致密Ba0.70Sr0.30TiO3陶瓷,系统研究了晶粒尺寸对居里温度TC、铁电相介电常数εF、峰值介电常数εM的影响规律,并深入分析了其内在的影响机理.研究表明:晶粒尺寸减小时,TC刚开始基本不变,直到晶粒尺寸小到一定程度时才开始降低,此变化规律可由Buesseum的内应力模型解释;随晶粒尺寸的增加,εF先增加后减小,此变化规律可由Shaikh的串并联模型来解释,主要影响因素有内应力、畴、晶界;εM随晶粒尺寸的增加,在晶粒尺寸较小时先增加后减小,晶粒尺寸较大时略有增加,此变化规律可由弥散相变理论和串并联模型共同解释,在晶粒尺寸较小时主要影响因素为内应力、微畴和晶界,晶粒尺寸较大时主要影响因素为晶界.
关键词:
0.70Sr0.30TiO3陶瓷')" href="#">Ba0.70Sr0.30TiO3陶瓷
介电常数
居里温度
晶粒尺寸 相似文献
9.
用直流磁控溅射法在(100)LaAlO3衬底上制备了La0.9Sr0.1MnO3薄膜.经退火处理后薄膜的原子力显微镜形貌观测和X射线衍射分析显示具有比较好的质量.电阻率-温度关系表明La0.9Sr0.1MnO3薄膜在281 K处发生金属绝缘体转变.电流在0.01—4 mA范围内,薄膜的峰值电阻率随电流增大而减小,在4 mA下获得了30.5%的峰值电阻率变
关键词:
掺杂锰氧化合物
0.9Sr0.1MnO3薄膜')" href="#">La0.9Sr0.1MnO3薄膜
电流诱导效应
相分离理论 相似文献
10.
Thin films of barium strontium titanate (Ba1−xSrx TiO3 (BSTO)) have been used in coupled microstrip phase shifters (CMPS) for possible insertion in satellite and wireless communication platforms primarily because of their high dielectric constant, low loss, large tunability, and good structural stability. In an attempt to improve the figure of merit K (phase shift °/dB of loss) of phase shifters, modification of the metal/BSTO interface of these devices has been done through surface modification of the BSTO layer using a self-assembled monolayer approach. The impact of this nanotechnology promises to reduce RF losses by improving the quality of the metal/BSTO interface. In this study, compounds such as 3-mercaptopropyltrimethoxysilane (MPS), 16-mercaptohexadecanois acid (MHDA) and 3-mercaptopropionic acid (MPA) were used to form the self-assembled monolayers on the BSTO surface. As a result of the previous modification, chemical derivatization of the self-assembled monolayers was done in order to increase the chain length. Chemical derivatization was done using 3-aminopropyltrimethoxysilane (APS) and 16-mercaptohexadecanoic acid. Surface chemical analysis was done to reveal the composition of the derivatization via X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared (FT-IR). Low and high frequencies measurements of phase shifters were done in order measure the performance of these devices for insertion in antennas. X-ray photoelectron spectroscopy characterization of modified BSTO thin films with MPS showed a binding energy peak at 162.9 eV, indicative of a possible SO interaction: sulfur of the mercapto compound, MPS, used to modify the surface with the oxygen site of the BSTO thin film. This interaction is at higher binding energies compared with the thiolate interaction. This behavior is observed with the other mercapto compounds such as: MHDA and MPA. An FT-IR analysis present a band at 780 cm−1, which is characteristic of an OSC stretching and reveals the modification of the BSTO thin film by the coupling of the O of the BSTO with the S of the mercapto compound. All the modification using mercapto compounds is through sulfur to the BSTO thin film. MHDA SAM on BSTO thin film was chemically derivatized using APS shown by XPS and FT-IR. The SAMs modified phase shifters showed an improvement in performance with respect to those phase shifters fabricated with standard methods. 相似文献
11.
采用改进的溶胶-凝胶方法在LaNiO3/Si(100)衬底上制备了MgO/(Ba0.8Sr0.2)TiO3多层薄膜.实验结果表明,MgO层的引入改变了(Ba0.8Sr0.2)TiO3的介电特性和漏电流行为,使薄膜的漏电 流降低了3个数量级,但介电常数也有相应降低.漏电流的显著降低是由MgO子层的高阻特性 以及微量Mg向(Ba0.8关键词:
0.8Sr0.2)TiO3多层薄膜')" href="#">MgO/(Ba0.8Sr0.2)TiO3多层薄膜
漏电流
介电常 数 相似文献
12.
Tunable and switchable Ba 0.5 Sr 0.5 TiO 3 film bulk acoustic resonators(FBARs) based on SiO 2 /Mo Bragg reflectors are explored,which can withstand high temperature for the deposition of Ba x Sr 1 x TiO 3(BST) films at 800 C.The dc bias-dependent resonance may be attributed to the piezoelectricity of the BST film induced by an electrostrictive effect.The series resonant frequency is strongly dc bias-dependent and shifts downwards with dc bias increasing,while the parallel resonant frequency is only weakly dc bias-dependent and slightly shifts upwards at low dc bias( 45 V) while downwards at higher dc bias.The calculated relative tunability of shifts at series resonance frequency is around 2.3% and the electromechanical coupling coefficient is up to approximately 8.09% at 60-V dc bias,which can be comparable to AlN FBARs.This suggests that a high-quality tunable BST FBAR device can be achieved through the use of molybdenum(Mo) as the high acoustic impedance layer in a Bragg reflector,which not only provides excellent acoustic isolation from the substrate,but also improves the crystallinity of BST films withstanding higher deposition temperature. 相似文献
13.
Seung U. Lee Mun Heum Park Jin Won Kim Hyeun Kyung Jo Won-Jeong Kim 《Applied Surface Science》2007,254(5):1493-1497
Ferroelectric BiFeO3 thin films with Nd-Cr (or Sm-Cr) co-substitution (denoted by BNdFCr and BSmFCr, respectively) were deposited on the Pt(2 0 0)/TiO2/SiO2/Si(1 0 0) substrates by a chemical solution deposition method. X-ray diffraction patterns revealed the formation of BNdFCr and BSmFCr thin films without any secondary phases. The co-substituted BNdFCr (or BSmFCr) thin films, which were annealed at 550 °C for 30 min in N2 atmosphere, exhibited enhanced electrical properties compared to BFO thin films with the remanent polarization (2Pr) and coercive electric field (2Ec) of 196, 188 μC/cm2 and 600, 570 kV/cm with the electric field of 800 kV/cm, respectively. The leakage current densities of BNdFCr and BSmFCr thin films measured at room temperature were approximately three orders of magnitude lower than that of BFO thin film, and the leakage current at room temperature of the thin films exhibited three distinctive conduction behaviors. Furthermore, the values of pulse polarizations [i.e., +(P*-P^) or −(P*-P^)] of BNdFCr and BSmFCr thin films were reasonably unchanged up to 1.4 × 1010 switching cycles. 相似文献
14.
Xiao-Fei ZhangQing Xu Han-Xing LiuWen Chen Min Chen Bok-Hee Kim 《Physica B: Condensed Matter》2011,406(8):1571-1576
Nonlinear dielectric properties of Ba0.6Sr0.4TiO3 ceramics prepared by citrate method were investigated under bias electric field with respect to field history. X-ray diffraction analysis and temperature dependence of the dielectric constant (εr) confirmed a macroscopically paraelectric state for the specimen at room temperature. A slim polarization versus electric field (P-E) hysteresis loop of the specimen at room temperature indicated the existence of polar nano-regions (PNRs) superimposed on the paraelectric background. The nonlinear dielectric properties in continuous cycles of bias field sweep displayed a strong sensitivity to the field history. This phenomenon was qualitatively explained in terms of an irreversible polarization evolution of the PNRs under the bias fields. A considerable decline of the tunability with the cycle number suggests an appreciable contribution of the PNRs to the dielectric nonlinearity. The polarization and size of the PNRs were determined by fitting the dielectric constants to a multipolarization mechanism model. 相似文献
15.
Wang Shu-Fang Yan Guo-Ying Chen Shan-Shan Bai Zi-Long Wang Jiang-Long Yu Wei Fu Guang-Sheng 《中国物理 B》2013,22(3):37302-037302
Three Bi2Sr2Co2Oy thin films with different microstructures have been prepared by chemical solution deposition on LaAlO3(001) through varying the annealing temperature. With the decrease in the annealing temperature, both the size and c-axis alignment degree of grains in the film decrease as well, leading to an increase in the film resistivity. In addition, the decrease in the annealing temperature also results in a slight increase in the seebeck coefficient due to the enhanced energy filtering effect of small-grain film. The nanostructured Bi2Sr2Co2Oy film with the average grain size of about 100 nm shows a power factor comparable to that of the films with larger grains. Since the thermal conductivity of the nanostrcutured films can be depressed due to the enhanced phonon scattering by grain boundary, a higher figure of merit is expected in Bi2Sr2Co2Oy thin film with grains in nanometer size. 相似文献
16.
Tin oxide (SnO2) thin films were deposited by radio frequency (RF) magnetron sputtering on clean corning glass substrates. These films were then annealed for 15 min at various temperatures in the range of 100-500°C. The films were investigated by studying their structural and electrical properties. X-ray diffraction (XRD) results suggested that the deposited SnO2 films were formed by nanoparticles with average particle size in the range of 23-28 nm. XRD patterns of annealed films showed the formation of small amount of SnO phase in the matrix of SnO2. The initial surface RMS roughness measured with atomic force microscopy (AFM) was 25.76 nm which reduces to 17.72 nm with annealing. Electrical resistivity was measured as a function of annealing temperature and found to lie between 1.25 and 1.38 mΩ cm. RMS roughness and resistivity show almost opposite trend with annealing. 相似文献
17.
W.S. Tan H.O. WangP. Dai H.P. WuX.S. Wu Q.J. JiaG.J. Hu J. Gao 《Physica B: Condensed Matter》2011,406(21):4115-4118
Perovskite manganite La0.9Ba0.1MnO3(LBMO) films were deposited on (0 0 1)-oriented single crystal yttria-stabilized zirconia (YSZ) substrate by 90° off-axis radio frequency magnetron sputtering. The film thickness ranged from 10 nm to 100 nm. Grazing incidence X-ray diffraction technique and high resolution X-ray diffraction were applied to characterize the structure of LBMO films. The LBMO film mainly consisted of (0 0 1)-orientated grain as well as weakly textured (1 1 0)-orientated grain. The results indicated that an amorphous layer with thickness of about 4 nm was formed at the LBMO/YSZ interface. The strain in LBMO film was small and averaged to be about -0.14%. The strain in the film was not lattice mismatch-induced strain but residual strain due to the difference in thermal expansion coefficient between film and substrate. 相似文献
18.
Titanium dioxide thin films have been prepared from tetrabutyl-orthotitanate solution and methanol as a solvent by sol-gel dip coating technique. TiO2 thin films prepared using a sol-gel process have been analyzed for different annealing temperatures. Structural properties in terms of crystal structure were investigated by Raman spectroscopy. The surface morphology and composition of the films were investigated by atomic force microscopy (AFM). The optical transmittance and reflectance spectra of TiO2 thin films deposited on silicon substrate were also determined. Spectroscopic ellipsometry study was used to determine the annealing temperature effect on the optical properties and the optical gap of the TiO2 thin films. The results show that the TiO2 thin films crystallize in anatase phase between 400 and 800 °C, and into the anatase-rutile phase at 1000 °C, and further into the rutile phase at 1200 °C. We have found that the films consist of titanium dioxide nano-crystals. The AFM surface morphology results indicate that the particle size increases from 5 to 41 nm by increasing the annealing temperature. The TiO2 thin films have high transparency in the visible range. For annealing temperatures between 1000 and 1400 °C, the transmittance of the films was reduced significantly in the wavelength range of 300-800 nm due to the change of crystallite phase and composition in the films. We have demonstrated as well the decrease of the optical band gap with the increase of the annealing temperature. 相似文献
19.
CdS doped TiO2 thin films (with CdS content=0, 3, 6, 9 and 12 at%) were grown on glass substrates. The X-ray diffraction analysis revealed that the films are polycrystalline of monoclinic TiO2 structure. The microstructure parameters of the films such as crystallite size (Dν) and microstrain (e) are calculated. Both the crystallites size and the microstrain are decreased with increasing CdS content. The optical constants have been determined in terms of Murmann's exact equations. The refractive index and extinction coefficient are increased with increasing CdS content. The optical band gap is calculated in the strong absorption region. The possible optical transition in these films is found to be an allowed direct transition. The values of Egopt are found to decrease as the CdS content increased. The films with 3 at% CdS content have better decomposition efficiency than undoped TiO2. The films with 6 at% and 9 at% CdS content have decomposition efficiency comparable to that of undoped TiO2, although they have lower band gap. The CdS doped TiO2 could have a better impact on the decomposing of organic wastes. 相似文献
20.
Hrudananda Jena Santanu Bera K.V. Govindan Kutty T.R.N. Kutty 《Applied Surface Science》2008,254(21):7074-7079
X-ray photoelectron spectroscopic (XPS) studies were carried out on wet-chemically synthesized cubic BaTiO3, Ba0.9Nd0.1TiO3 and BaTi0.9Fe0.1O3−δ powders. The compounds were prepared by hydrothermal and gel to crystallite conversion technique; and phases formed readily at 420 K. The phase purity of the powders was confirmed from X-ray diffractometry. Chemical state and chemical environment of the constituent elements in the compositions were examined by XPS. Ba2+ was found to exist in two different chemical environments in these titanates. The Ti 2p3/2 photoelectron peak in BaTi0.9Fe0.1O3−δ was found to be broadened after Fe3+ substitution. Any resolvable broadening was not observed distinctly in the Ti 2p peak for Ba0.9Nd0.1TiO3, unsintered BaTiO3 and BaTiO3 annealed in hydrogen (8% H2 + Ar) at 1000 K. The prevalence of mixed-valent titanium and iron in BaTi0.9Fe0.1O3−δ composition was evident from the XPS results and was further supported by the enhanced electrical conductivity at 298-550 K for BaTi0.9Fe0.1O3−δ in comparison to BaTiO3 and Ba0.9Nd0.1TiO3. Hydroxyl incorporation was facilitated by substituting Nd3+ in Ba-sublattice. The presence of hydroxyls was observed from the broadening of the O 1s peak in XPS studies of the compounds. 相似文献