共查询到20条相似文献,搜索用时 15 毫秒
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Slawomir M. Kaczmarek Taiju Tsuboi Yosuke Nakai Marek Berkowski Wei Huang Zbigniew Kowalski 《Materials Science-Poland》2014,32(1):7-11
Bi4Ge3O12 single crystals were obtained using Czochralski growth method. Photoluminescence spectra were analyzed versus temperature from 12 to 295 K. Besides the previously observed emission bands at 610 and 820 nm, the new emission band at 475 nm was found by a careful temperature dependence measurement in the present study. The influence of basic and defect structure on the shape and position of the spectra versus temperature was discussed. 相似文献
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We report on the fabrication of the planar waveguides in Bi4Ge3O12 crystal by using 17 MeV C5+ or O5+ ions at a fluence of 2×10(14) ions/cm2. The reconstructed refractive index profiles of the waveguides produced by either C5+ or O5+ irradiation are the "well" + "barrier" pattern distribution. The two-dimensional modal profiles of the planar waveguides, measured by using the end-coupling arrangement, are in good agreement with the simulated modal distributions. After thermal annealing treatment at 260 °C for 30 min, the propagation loss for C5+ and O5+ irradiated waveguides could be reduced down to ~1.1 and ~4.8 dB/cm, respectively, which exhibit acceptable guiding qualities for potential applications in integrated optics. 相似文献
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E. F. Riebling 《Journal of Materials Science》1975,10(9):1565-1570
Ternary thallium and sodium bismuth germanate glasses were prepared and their densities refractive indices, and infra-red spectra obtained. The effect of univalent cations on the stability of the arrangement of decoupled GeO4 tetrahedra in amorphous Bi4Ge3O12 was compared with the effect of divalent cations. The molar volumes of glasses with the nominal mol% composition 20 M2O(MO).20 Bi2O3.60 GeO2 are directly related to the size and charge type of Mz+. However, the molar volumes of such glasses are inversely related to the ionic potential (z/r) of Mz+. The infra-red spectra of these ternary glasses exhibitv Ge?O shifts that reflect the presence of both isolated and small clusters of GeO4 tetrahedra compared to amorphous Bi4Ge3O12. This slight increase in the degree of polymerization appears to be directly related to the ionic potential of Mz+. 相似文献
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制备晶粒形貌生长各向异性的中间化合物Bi4Ti3O12粉体是采用流延成型和模板晶粒生长(TGG)等工艺方法制备(Na0.5Bi0.5)TiO3基无铅压电织构陶瓷的关键技术.以NaCl-KCl熔盐法制备了生长各向异性的Bi4Ti3O12粉体,利用X射线衍射和扫描电子显微镜研究了非化学计量Bi2O3对粉体相结构和微观形貌的影响,优化了制备Bi4Ti3O12粉体的工艺参数,并探讨了Bi4Ti3O12粉体在熔盐中的生长机理.研究表明,随着Bi2O3过量程度的增加,所得Bi4Ti3O12粉体颗粒的平均尺寸和均匀程度均增加,当Bi2O3过量7.5%时达到最佳值,其平均粒径为8~10 μm. 相似文献
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V. Marinova S. H. Lin K. Y. Hsu Mei-Li Hsieh M. M. Gospodinov V. Sainov 《Journal of Materials Science: Materials in Electronics》2003,14(10-12):857-858
Bi4Ge3O12 single crystals doped with different concentration of Ru were grown by the Czochralski technique. Optical absorption bands were induced by illumination with ultraviolet light at room temperature. The absorption coefficient values increased with increasing ruthenium concentration. The induced photochromic effect was completely reversible: all samples recovered their transparency after thermal treatment. Preliminary holographic recording experiments showed a fast response time and a relatively slow erase time during the reading process. 相似文献
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采用熔盐法制备了板状Bi4Ti3O12微晶.用示差扫描量热-热重分析(DSC-TG)、X射线衍射(XRD)及扫描电镜(SEM)研究了不同温度对合成Bi4Ti3O12相结构与形貌的影响.结果表明,板状Bi4Ti3O12微晶的最佳合成温度为800~1000℃,低于800℃合成产物中容易出现杂相;1030℃时Bi4Ti3O12出现结构变化;1165℃出现杂相Na0.5Bi0.5Ti7O27;温度继续升高到1250℃时Bi4Ti3O12出现分解.实现板状Bi4Ti3O12微晶形貌可控的最佳温度范围为850~950℃. 相似文献
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X. Huang D. Jaque F. Vereda B. Fonrobert P. J. Chandler P. D. Townsend 《Journal of Modern Optics》2013,60(8):1731-1743
Abstract The ‘optical writing’ of permanent channel waveguides in the surface of He+ ion-implanted bismuth germanate, Bi4Ge3O12, has been studied, using end-coupled argon and Ti:sapphire CW laser beams. Comparisons of the self-focusing effect in waveguides and bulk samples have been made for both Nd3+ doped and undoped material. The permanent ‘writing’ effect has been compared with the structural change observed earlier in ion-implanted Bi4Ge3O12 waveguides annealed at high temperature. 相似文献
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To assess the suitability of bismuth germanate as an electro-optic material for high precision applications, we have confirmed and extended previous data on its refractive index, electro-optic tensor element r(41), and thermal expansion coefficient. In addition, we have measured the thermo-optic coefficient dn/dT, the temperature dependence of the electro-optic coefficient, and the stress-optic tensor elements. From the stress-optic tensor elements and previously published data, we have computed the strain-optic tensor elements. The index of refraction is given, to a good approximation, by the single-term Sellmeier equation, n(2) - 1 = S(0)λ(0)(2)/[1 - (λ(0)/λ)(2)], with S(0) = 95.608 μm(-2) and λ(0) = 0.1807 μm. The thermo-optic coefficient is 3.9 × 10(-5)/°C at 632.8 nm and 3.5 × 10(-5)/°C at 1152.3 nm. The electro-optic tensor element varies between approximately 1.05 and 1.11 pm/V over the spectral range of 550-1000 nm; its normalized effective change with temperature is approximately 1.54 × 10(-4)/°C. The thermal expansion coefficient is 6.3 × 10(-6)/°C over the range 15-125 °C. Values of the stress-optic tensor elements are q(11) - q(12) = -2.995 × 10(-13) m(2)/N and q(44) = -0.1365 × 10(-12) m(2)/N. The strain-optic tensor elements are p(11) - p(12) = -0.0266 and p(44) = -0.0595. 相似文献
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The piezoelectric constantsd
11,d
22 andd
33 for a single domain single crystal of Bi4Ti3O12 have been measured at room temperature using appropriate crystal cuts on a Berlincourtd
33 meter. From the known temperature dependence of the spontaneous polarization, lattice strain and dielectric permittivity, the equivalent piezoelectric constants have been calculated assuming a simple proper ferroelectric in which,P
s, is the order parameter. Constants in the plane of the perovskite-like sheets in the Bi4Ti3O12 structure (d
11,d
22) show good agreement with experimental values. The calculated value of the constantd
33 is more than an order of magnitude larger than the experimentally-measured value and gives clear indication of the indirect coupling to the strain in the tetrad axial direction and the need for a more sophisticated phenomenology. 相似文献
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Tajiri T Sumitani K Haruki R Kohno A 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(12):2574-2578
Polycrystalline thin films of La-substituted bismuth titanate (BLT) were formed directly on p-type Si(100) substrates by using sol-gel and spin coat methods. The BLT film and interfacial layer between BLT and Si were quantitatively investigated by the X-ray reflectivity method. Also, crystal orientations of sub-100-nm-thick BLT thin films were confirmed by X-ray diffraction using a synchrotron radiation source. The preferred c-axis orientation normal to the surface depended on the crystallization temperature. The difference in the preferred c-axis orientations of the BLT films caused the difference in the hysteresis voltage width in the capacitance-voltage characteristics of Au/BLT/p-Si structures. Furthermore, the c-axis of the Bilayered structure was preferentially oriented and aligned in the in-plane direction. 相似文献
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《Materials Science and Engineering: B》2007,136(1):1-4
Natural-superlattice-structured ferroelectric thin films, Bi3TiNbO9–Bi4Ti3O12 (BTN–BIT), have been synthesized on Pt/Ti/SiO2/Si by metal organic decomposition (MOD) using BTN–BIT (1 mol:1 mol) solution. BTN–BIT films show natural-superlattice peaks below 2θ = 20° in X-ray diffraction patterns, which indicate that the BTN–BIT films annealed at 700–800 °C in O2 ambient are consisted of iteration of two unit cells of Bi3TiNbO9 and one unit cell of Bi4Ti3O12. As the annealing temperature increases from 600 to 750 °C, uniform and crack-free films, better crystallinity and ferroelectric properties can be obtained, but the pyrochlore phase in BTN–BIT films annealed over 800 °C would impair the ferroelectric properties. With the increase of O2 flow rate from 0.5 to 1.5 L/min, both remanent polarization Pr and coercive electric field EC increase, which are mainly attributed to reduction of the vacanvies of Bi and oxide ions in the films. Natural-superlattice-structured BTN–BIT thin films having 2–1 superlattice annealed at 750 °C in O2 ambient with a flow rate of 1.5 L/min exhibit superior ferroelectric properties of Pr = 23.5 μC/cm2 and EC = 135 kV/cm. 相似文献
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Inorganic Materials - We have studied the influence of high gamma doses and dose rates on the light output of bismuth orthogermanate (Bi4Ge3O12) crystals. The results demonstrate that the change in... 相似文献
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C. Jovalekic Lj. Atanasoska V. Petrovic M. M. Ristic 《Journal of Materials Science》1991,26(13):3553-3564
Polycrystalline ferroelectric Bi4Ti3O12 ceramics have been prepared by the method of reactive liquid phase sintering. The sintering behaviour of the Bi2O3-TiO2 composite was examined by plotting the isothermal densification curves. The results indicate that the starting oxides are involved in the reaction even at temperatures lower than or equal to 800°C, but the reaction advances at a very slow rate. Above solidus, the liquid phase promotes an extended reaction. Saturation observed in two densification curves, at 875 and 1100°C demonstrate that the reaction proceeds by two steps. A completion of the Bi4Ti3O12 formation occurs after 60 min of sintering at 1100°C. Optical micrographs of sintered bismuth titanate ceramics show randomly oriented ferroelectric grains separated by a paraelectric intergranular layer. The Bi4Ti3O12 crystallites exhibit a platelike morphology, similar in the appearance to mica, as evidenced by scanning electron micrographs. Isothermal annealing (750 to 950°C) does not affect the microstructure and electric properties of sintered bismuth titanate. The considerable value of dielectric permittivity and the appearance of hysteresis have been correlated to the presence of oxygen vacancies within the pseudotetragonal structure of Bi4Ti3O12. The oxygen vacancies are preferentially sited in the vicinity of bismuth ions as evidenced by X-ray photoemission data. XPS and AES measurements confirm that the surface concentration of cations comprising the Bi4Ti3O12 ceramics does not deviate from the nominal bulk composition. 相似文献
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L.F. Xu P.B. Qi S.S. Chen R.L. Wang C.P. Yang 《Materials Science and Engineering: B》2012,177(6):494-498
Ca1?3x/2BixCu3Ti4O12 (x = 0.0–0.3) ceramics were prepared by the conventional solid-state reaction method. X-ray powder diffraction analysis confirmed the formation of cubic CCTO phase except for subtle peaks of CuO. SEM micrographs suggested that the morphologies of doped CCTO ceramics had been sheet-like for high Bi-doping amount, and the dominant grain size decreasing could be seen for the small content of Bi-doping CCTO. Dielectric properties of pure and doped CCTO were investigated in a broad temperature range of 20–420 K. The results showed that bismuth doping could decrease the dielectric loss but suppress the dielectric temperature stability at the same time. Bi doped CCTO ceramics presented different relaxation properties. As to pure CCTO and BCCTO (x = 0.3) only one MW relaxation (Relaxation I) could be found, which moves to higher frequency with temperature increasing. However, two relaxation processes (Relaxation I and II) appear for BCCTO (x = 0.1–0.2). By means of complex impedance spectra analysis and Arrhenius fitting, we successfully separated the different conductive segments and explained the mechanisms of the two relaxation processes. Relaxation I appeared at low temperature could be attributed to the VO doping energies inside CCTO grains which did not showed significant changing of activation energy after bismuth doping. For Relaxation II at higher temperature than Relaxation I, with activation energy obviously depending on the Bi-ion concentration, may be related with the VO point defects at the grain boundaries. 相似文献
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以Si(OC2H5)4和Bi(NO3)3·5H2O作为前驱体、柠檬酸作为溶剂, 按化学计量比配料, 采用溶胶-凝胶法合成并经高温烧结制备了纯相Bi4Si3O12多晶粉末, 每批次可合成250 g。以此为原料、<001 >取向BSO为籽晶, 在坩埚下降炉内生长了BSO晶体, 讨论了晶体的析晶行为, 获得了30 mm × 30 mm × 210 mm的高质量BSO晶体。闪烁性能测试表明, 该晶体能量分辨率为18.9%, 光输出为同等条件下CSI(T1)晶体的7.2%。 相似文献