共查询到20条相似文献,搜索用时 230 毫秒
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通过温度依赖的透射和反射光谱研究了在准同型相界附近的Pb(Mg_(1/3)Nb_(2/3))O_3-0.3PbTiO_3(PMN-0.3PT)单晶光学性质.这种禁带宽度随温度范围不同变化规律不同现象,揭示了PMN-PT单晶温度依赖的复杂相结构.禁带宽度Eg在303 K是3.25 e V,临界点Ea是3.93 e V,临界点Eb是4.65 e V,它们随着温度的上升而下降,在453 K禁带宽度Eg是3.05 eV,临界点Ea是3.57 eV,临界点Eb是4.56 eV.这三个跃迁能量Eg、Ea、Eb分别对应从O 2p到Ti d、Ni d、Pb 6p轨道跃迁.它们随温度上升而下降的变化规律可以用晶格热膨胀和电子声子相互作用理论来解释.通过Tauc-Lorentz色散模型拟合得到了303 K到453 K温度范围的Pb(Mg_(1/3)Nb_(2/3))O3-0.3PbTiO_3单晶光学常数及其随温度的变化规律,发现折射率n随着温度的升高而升高. 相似文献
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该文研究了在新型压电材料YCa4O(BO3)3(YCOB)上设计和制备高温声表面波(SAW)谐振器。研究了2种不同切型X-90°、Z-90°YCOB为基底的SAW谐振器的高温性能。研究表明,在600℃下器件的稳定性高,其谐振频率随着温度的升高呈线性降低。Z-90°YCOB器件的谐振频率和温度灵敏度分别为278.94 MHz和21.22kHz/℃;X-90°YCOB器件的谐振频率和温度灵敏度分别为230.53MHz和13.44kHz/℃。结果表明,Z-90°切型的YCOB的温度灵敏度较高。 相似文献
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研究了SAW延时与AlN膜(用有机金属化学蒸发沉淀法在Al_2O_3基片上生长的)的温度关系.当SAW沿着[1100]Al_2O_3方向传播时,AlN/Al_2O_3的延时温度系数随KH增加而降低,其中K是波数,H是AlN膜的厚度.我们在一定的KH值下成功地获得了零温度系数的声表面波延迟线. 相似文献
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批量生产L_iT_aO_3晶体的工艺技术现已建立起来了。这一工艺成本低廉,生长的L_iT_aO_3晶体能够用来制作声表面波(SAW)电视中频滤波器。用提拉法,在铂—铑坩埚中已成功地沿α轴拉制出用于SAW的L_iT_wO_3单晶直径达62—75mm,长度为130mm。具有水平取向的圆形x切刈基片是在圆柱晶锭上切出的,厚度为500μm。如果声表面波在x切割基片上沿112°y传播,则可以把体波寄生信号响应抑制到-40dB以下。它具有低的温度系数(~18ppm/℃)和合适的耦合常数(K~2~0.75%)。实际应用证明,声表面波的各种特性不受晶体中杂质(铑)浓度以及L_i与T_a的组份比的影响,但却对电畴反转是否充分很为敏感。 相似文献
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声表面波理论是研究高性能声表面波器件的理论基础。耦合模理论因能正确、全面反映声表面波在压电材料上的传播特性得到广泛的重视。应用耦合模理论分析推导自行研制的Y型声表面波器件特性,并编制相应的软件包。应用该软件包计算Y型声表面波器件中心频率处的插入损耗(-12.6dB)与实验结果(约-13dB)相近,为声表面波器件提供一种有效的分析工具。 相似文献
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二、导波结构的声光互作用1.声表面波和光导波(1)声表面波声表面波指的是沿着固体表面传播而振幅随着深度迅速减弱的弹性波.已经发现的声表面波有瑞利波,乐甫波和斯托尼莱波等.在目前,应用最广研究最多的是瑞利波.瑞利波是沿着固体自由表面传播的非均匀 相似文献
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The Contributions of Polar Nanoregions to the Dielectric and Piezoelectric Responses in Domain‐Engineered Relaxor‐PbTiO3 Crystals 下载免费PDF全文
The existence of polar nanoregions is the most important characteristic of relaxor‐based ferroelectric materials. Recently, the contributions of polar nanoregions to the shear piezoelectric property of relaxor‐PbTiO3 (PT) crystals are confirmed in a single domain state, accounting for 50%–80% of room temperature values. For electromechanical applications, however, the outstanding longitudinal piezoelectricity in domain‐engineered relaxor‐PT crystals is of the most significance. In this paper, the contributions of polar nanoregions to the longitudinal properties in [001]‐poled Pb(Mg1/3Nb2/3)O3‐0.30PbTiO3 and [110]‐poled Pb(Zn1/3Nb2/3)O3‐0.15PbTiO3 (PZN‐0.15PT) domain‐engineered crystals are studied. Taking the [110]‐poled tetragonal PZN‐0.15PT crystal as an example, phase‐field simulations of the domain structures and the longitudinal dielectric/piezoelectric responses are performed. According to the experimental results and phase‐field simulations, the contributions of polar nanoregions (PNRs) to the longitudinal properties of relaxor‐PT crystals are successfully explained on the mesoscale, where the PNRs behave as “seeds” to facilitate macroscopic polarization rotation and enhance electric‐field‐induced strain. The results reveal the importance of local structures to the macroscopic properties, where a modest structural variation on the nanoscale greatly impacts the macroscopic properties. 相似文献
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WEN Chuan-jing YANG Ji-sheng 《光电子快报》2005,1(1):1-4
We use Joness matrix method and the global optimal method to investigate the propagation characteristic of surface acoustic wave(SAW) for X-cut single crystal Lithium Niobate(LiNbO3 ). As an application, a novel integrated acousto-optical filter,which allows to minimize the dimension of AO cells and suppress side-lobes,was designed on the base of LiNbO3 crystal. 相似文献
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Ta2O5 single crystals have been grown by the laser heated pedestal growth (LHPG) technique up to several centimeters length with diameter of 1.1 mm. The crystal, characterized by X-ray diffraction, dielectric measurement, and thermal expansion analysis, has Htri-Wa2O5 symmetry. Dielectric permittivity, loss tangent along [001] and [110] direction were investigated over the temperature range from -180℃ to 100℃. Large dielectric anisotropy in 2O5 single crystal was observed. At room temperature, the dielectric permittivities (1 MHz) along [001] and [110] are 33.2 and 231.9, respectively. The reason of dielectric enhancement in Ta2O5 crystal grown by LHPG was also discussed. 相似文献
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Yifan Wang Feng Yang Xuanze Li Fan Ru Pei Liu Li Wang Wei Ji Jing Xia Xiangmin Meng 《Advanced functional materials》2019,29(43)
Inorganic cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) is a promising material for developing novel electronic and optoelectronic devices. Despite the substantial progress that has been made in the development of large perovskite single crystals, the fabrication of high‐quality 2D perovskite single‐crystal films, especially perovskite with a low symmetry, still remains a challenge. Herein, large‐scale orthorhombic CsPbBr3 single‐crystal thin films on zinc‐blende ZnSe crystals are synthesized via vapor‐phase epitaxy. Structural characterizations reveal a “CsPbBr3(110)//ZnSe(100), CsPbBr3[?110]//ZnSe[001] and CsPbBr3[001]//ZnSe[010]” heteroepitaxial relationship between the covering CsPbBr3 layer and the ZnSe growth substrate. It is exciting that the epitaxial film presents an in‐plane anisotropic absorption property from 350 to 535 nm and polarization‐dependent photoluminescence. Photodetectors based on the epitaxial film exhibit a high photoresponsivity of 200 A W?1, a large on/off current ratio exceeding 104, a fast photoresponse time of about 20 ms, and good repeatability at room temperature. Importantly, a strong polarization‐dependent photoresponse is also found on the device fabricated using the epitaxial CsPbBr3 film, making the orthorhombic perovskite promising building blocks for optoelectronic devices featured with anisotropy. 相似文献
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All the six lattice parameters (a, b, c, alpha, beta and gamma) of a Si (001) layer grown on a sapphire (1102) substrate were determined by convergent-beam electron diffraction with no assumption of crystal lattice symmetry. A lattice compression in the Si (001) plane and an elongation in the [001] direction were revealed. An anisotropic lattice compression in the (001) plane was clearly detected for the first time. That is, the lattice compression in the Si [100] direction, which is parallel to the sapphire [1101] direction, was larger than that of the Si [010] direction, which is parallel to the sapphire [1120] direction. It was also revealed that the lattice parameters of the Si-layer depend on the distance from the interface. Anisotropy of carrier mobility was reasonably explained in terms of the anisotropy of the lattice parameters determined. 相似文献
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准同型相界附近PMN-PT材料的制备和性能 总被引:2,自引:0,他引:2
对铁电菱方(FR)-铁电四方(FT)准同型相界附近的铌镁酸铅(PMN)-钛酸铅(PT)材料制备方法和介电、压电和热释电性能进行了系统的研究: 相似文献
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The growth parameters and ferroelectric properties of SBN and lead-modified SBN single crystals grown by the Czochralski method
have been investigated. All crystals were grown in the [001] direction in air. It was observed that the degree of difficulty
of growth increased as the diameter and Ba content of the crystal increased. Crack-free single crystals ~ 1. cm in diameter
have been grown. The temperature dependence of pyroelectric properties have been studied. Poled SBN (x=0.5) with the very
low loss factor of 0.003 has been obtained. High detectivity pyroelectric infrared detectors have been made from these low
loss crystals. 相似文献
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The solvo-thermal technique is used for the synthesis of [Mn(en)3]Te4 (I).The crystal structure has been determined by single crystal X-ray diffraction techniques.The crystal belongs to the monoclinic, space group p21/c with unit cell:a=0.8461(1),b=1.5653(2), c=1.4269(2)nm, α=90°,β=91.37(1) (3)°, γ=90°,V=1.8893(4)nm3,and Z=4.The results show that the structure contains a linear chain Zintl anion,[Te4]2-and a complex cation,[Mn(en)3]2+. Optical studies have been performed on the powder sample of I, suggesting that the compound is a semiconductor with a band gap of 0.73eV. The semiconductor properties for MnQ2(Q=S,Se,Te) and [Mn(en)3]Te4 have been discussed by molecular orbital theory. 相似文献
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Kishida K Miyata M Wada N Okamoto NL Tanaka K Inui H Koyama H Hattori T Iriyama Y Ogumi Z 《Journal of electron microscopy》2007,56(6):225-234
The crystal and defect structures of coarse-grained crystals of La(2/3-x)Li(3x)TiO3 grown from the melt by the Tammann-St?ber method were studied by transmission electron microscopy and powder X-ray diffraction. The as-grown crystals of La(2/3-x)Li(3x)TiO3 have a Li-poor composition of La(0.57)Li(0.29)TiO3 and a diagonal-type unit cell of 2(1/2)a(p) x 2(1/2)a(p) x 2a(p) with the tetragonal symmetry [space group: P4/nbm (#125)] due to both the La-cation ordering and the tilting of TiO6 octahedra. The secondary La2Ti2O7 phase precipitates in the form of plates in the La(2/3-x)Li(3x)TiO3 phase with the orientation relationships of 001(p)//[100](La2Ti2O7) and {110}(p)//(001)(La2Ti2O7), which may cause detrimental effects to ionic conductivity. 相似文献