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1.
通过用中子非弹性散射测量旋声晶体高对称方向的横声学支声子色散曲线的劈裂,从三个方面研究了同构异质晶体Bi_(12)GeO_(20)和Bi_(12)SiO_(20)的旋声特性。值得注意的是,沿〈111〉方向传播的左旋、右旋圆偏振声子具有不同的衰减。其中传播速度快的圆偏振声子衰减较大,该结论为这两种晶体所证实,这是在晶体旋声性研究中首次观察到的现象。实验还直接确定了衰减较大的这支声子的寿命约为2×10~(-11)S。  相似文献   

2.
用下降法制备了Bi4Ge3O12晶体,发现生长出来的圆柱状晶体外侧呈现淡红色。对红色Bi4Ge3O12晶体进行了低温(至8 K)下的近红外发射光谱及衰减寿命等测试分析。发现低温时(200 K以下)红色Bi4Ge3O12在1 150 nm等波长处有较强的发射峰,强度随温度降低而增强,衰减时间为几百μs。  相似文献   

3.
沈志工  陶昉  马文漪  林泉 《物理学报》1988,37(2):214-220
用中子相干非弹性散射、沿三个主晶轴方向测量了同构异质晶体NaBrO3和NaClO3的声子色散关系。从小波矢区的实验结果获得了沿晶体这些方向的弹性波速及三个独立的弹性常数C11,C12,C44。实验结果表明,尽管这两种晶体在旋声方面表现出十分不同的特性,但是,它们的左旋和右旋圆偏振声子的声速都是在一个特定的平均速度v(TD)上下均衡的分布,这个平均速度可由 关键词:  相似文献   

4.
La掺杂对Bi4Ti3O12薄膜铁电性能的影响   总被引:4,自引:0,他引:4       下载免费PDF全文
郭冬云  王耘波  于军  高俊雄  李美亚 《物理学报》2006,55(10):5551-5554
利用Sol-Gel法在Pt/Ti/SiO2/Si衬底上制备出Bi4Ti3O12和Bi3.25La0.75Ti3O12薄膜,研究了La掺杂对Bi4Ti3O12薄膜的晶体结构、铁电性能和疲劳特性的影响,发现La掺杂没有改变Bi4Ti3O12薄膜的基本晶体结构,并且提高了Bi4Ti3O12铁电薄膜的剩余极化值和抗疲劳性能,对La掺杂改善Bi4Ti3O12铁电薄膜性能的机理进行了讨论. 关键词: 铁电性能 4Ti3O12薄膜')" href="#">Bi4Ti3O12薄膜 3.25La0.75Ti3O12薄膜')" href="#">Bi3.25La0.75Ti3O12薄膜 sol-gel法 La掺杂  相似文献   

5.
测量了Bi2Sr2CaCu2O8单晶a方向的热电势率Sa和b方向的热电势率Sb与温度T的关系,发现在a-b平面内热电势率存在各向异性。认为Sa与Sb的差异来源于b方向的调制结构,并用扩散热电势率Sd,声子曳引热电势率Sg和相关跳跃热电势率Sh三种贡献,对实验结果进行了 关键词:  相似文献   

6.
在可见光范围测量了Bi4Ge3O12晶体磁光法拉第旋转的色散关系,也测量了从室温到液氮温度磁光旋转在633nm的变化。大的磁光旋转和很宽光波范围的高透过率表明晶体在磁光应用上也是很有价值的。扼要讨论了Bi离子在抗磁晶体中对磁光旋转的重要作用。 关键词:  相似文献   

7.
王华  任明放 《物理学报》2007,56(12):7315-7319
采用溶胶凝胶工艺在p-Si衬底上制备了SrBi2Ta2O9/Bi4Ti3O12复合铁电薄膜. 研究了SrBi2Ta2O9/Bi4Ti3O12复合薄膜的微观结构与生长行为、铁电性能和疲劳特性. 研究表明: Si衬底Bi4Ti< 关键词: 2Ta2O9')" href="#">SrBi2Ta2O9 4Ti3O12')" href="#">Bi4Ti3O12 复合铁电薄膜 溶胶凝胶工艺  相似文献   

8.
王华  任鸣放 《物理学报》2006,55(3):1512-1516
在溶胶-凝胶工艺获得高质量Bi4Ti3O12薄膜的基础上 ,制备了Ag/Bi4Ti3O12栅n沟道铁电场效应晶体管. 研 究了Si基Bi4Ti3O12薄膜的生长特性及其对铁电薄膜/ 硅的界面状态和铁电场效应晶体管存储特性的影响. 研究表明,在合理的工艺条件下可以获 得具有较高c-轴择优取向的纯钙钛矿相Si基Bi4Ti3O12 铁电薄膜并有利于改善Bi4Ti3O12/Si之间的界面特性; 顺时针回滞的C-V特性曲线和C-T曲线表明Ag/Bi4Ti3O12栅n沟道铁电场效应晶体管具有极化存储效应和一定的极化电荷保持能力; 器件的转移(I< sub>sd-VG)特性曲线显示Ag/Bi4Ti3O12栅n沟道铁电场效应晶体管具有明显的栅极化调制效应. 关键词: 铁电场效应晶体管 4Ti3O12')" href="#">Bi4Ti3O12 存储 特性 溶胶-凝胶工艺  相似文献   

9.
俞平胜  苏良碧  徐军 《发光学报》2015,36(3):283-287
生长了Mg、Ca离子掺杂(提拉法)和Cl离子掺杂(坩埚下降法)的Bi4Ge3O12(BGO)晶体,测试了晶体样品的吸收谱、光致发光谱和发光衰减时间等。这些掺杂的BGO晶体的可见光发光比纯BGO有所减弱,但在808 nm和980 nm激光二极管(LD)激发下出现了纯BGO几乎没有的近红外发光,归因于改变了能级的Bi离子或可能出现的低价态Bi离子。掺杂对近红外发光的影响跟掺杂离子价态有关,同价态的掺杂离子对近红外发光的影响相差不大。  相似文献   

10.
Si基Bi4Ti3O12铁电薄膜的制备与特性研究   总被引:11,自引:6,他引:5       下载免费PDF全文
王华 《物理学报》2004,53(4):1265-1270
采用sol-gel工艺, 在分层快速退火的工艺条件下成功地制备了高质量Si基Bi4Ti3O12铁电薄膜. 研究了Si基Bi4Ti3O12薄膜的生长行为、铁电性能、C-V特性和疲劳特性. 研究表明: Si基Bi4Ti3O12薄膜具有随退火温度升高沿c轴择优生长的趋势; 退火温度通过影响薄膜的晶粒尺寸、生长取向和薄膜中载流子的浓度来改变Si基Bi关键词: sol-gel法 铁电薄膜 4Ti3O12')" href="#">Bi4Ti3O12 C-V特性  相似文献   

11.
Acoustical activity of Bi12GeO20 has been studied by measuring the splitting of the degeneracy of transverse acoustical waves propagating along the directions corresponding to acoustical axes, [100] and [111] with neutron inelastic scattering. A comparison with the experimental results of α-SiO2 and NaClO3 has been done. Three striking features of acoustical activity can be obtained from the present study. One of them is that the attenuation is different for right circularly polarized mode of acoustical phonon propagating along acoustical axes from left one. This effect might have applications in the future.  相似文献   

12.
Laevorotatory crystals of isomorphous Bi12SiO20 and Bi12GeO20 are shown, by use of the anomalous X-ray scattering component in the structure amplitudes, to have identical chirality (handedness of atomic arrangement) in contrast with the case of NaC103 and NaBrO3, in which crystals of the same chirality rotate plane polarized light in opposite senses.  相似文献   

13.
Absorption of Bi12GeO20 and Bi12SiO20 single crystals doped with Mn and Cr were investigated before and after illumination with visible light. Pronounced photochromic effects were found. The effects are explained in terms of light induced charge transfer Mn4+→Mn5+ and Cr3+→Cr2+.  相似文献   

14.
Based on a classical two-exposure holographic technique, real-time image subtraction is obtained in four-wave mixing of a reflection hologram type with highly sensitive photorefractive Bi12GeO20 crystals. This method takes advantage of the relatively slow response and erasure times of holographic recording in Bi12GeO20 crystals.  相似文献   

15.
From Raman data and a group-theoretical analysis, we deduce that in Bi12GeO20 and Bi12SiO20 there are four weakly bound oxygen atoms and a tightly bound unit MO4, where M = Ge or Si. Some normal modes of the tightly bound units are identified in Raman and in infrared reflection data. The kinds of interatomic binding forces in these crystals are determined. The results are compared with structure data determined by X-ray scattering.  相似文献   

16.
Some characteristic peculiarities of the volume phase holograms in a high-sensitive electrooptic Bi12SiO20 crystals such as polarization properties of the diffracted light beam and nonlinear phenomena in the stationary stage of the hologram formation are investigated. Spatial frequency mixing or combinational hologram writing by means of non-linearity of the holographic process is discussed as a new promising technique of the volume holography. In particular two important problems of Bi12SiO20 crystals: nondestructive readout at the wavelength different from that of the writing beams and correlation analysis of complex two-dimensional pictures can be solved by this method.  相似文献   

17.
Real-time image division is obtained by using four-wave mixing of a reflection hologram type with photorefractive Bi12GeO20 crystals. This method utilizes the nonlinear characteristic of four-wave mixing which reverses the phase of the incident wave.  相似文献   

18.
We present a recent development in holography with multimode, large free-spectral range (FSR) diode lasers in photorefractive sillenite crystals. A novel refractometry method based on this type of holographic recording in Bi12TiO20 (BTO) crystals is proposed. The holographic image of a prism-shaped transparent sample appears covered of interference fringes, and as the sample is properly translated, the fringes run along the holographic image. An expression providing the refractive index of the medium as a function of the sample displacement and the correspondent number of running fringes was derived. The refractive indexes of optical (BK7) glass, ethanol, hexan, cumene and aqueous solution of NaCl with different concentrations were measured in order to test the method. The obtained results are in good agreement with the ones reported in literature or measured by us using a commercial Abbe refractometre.  相似文献   

19.
The fundamental reflectivity spectrum in the energy range 1.5–8.5 eV is reported for Bi12GeO20 (BGO) single crystals. From a Kramers-Kronig analysis the optical constants of BGO are computed. An energy level scheme for interband optical transitions is proposed. A value of 0.7 eV for the spin-orbit splitting of the valence band is suggested. Some features of the band structure are discussed, and the correlations between the band structures of BGO and A2VB3VI-compounds are indicated. The experimental premises for possible simplifications of a theoretical calculation of the band structure are given.  相似文献   

20.
Optical absorption and ESR spectra of Bi12GeO20 doped with Cr were measured before and after illumination with visible light. It was found that Cr4+ ions in tetrahedral position are responsible for light induced ESR and optical spectra. The g-factor of the center is 1.945 ± 0.002. Crystal field parameters for the Cr4+ center are Dq = 820 cm?1 and B = 429cm?1. The photochromic effect is explained in terms of a Cr5+?Cr4+ charge transfer process.  相似文献   

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