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1.
Growth of undoped and Cr doped (0.1, 0.25 and 0.5 mol % Cr2O3) congruently‐ melting‐composition LiNbO3 single crystals by Czochralski technique is reported. Chromium doping was optimised to get crystals with potential for an integrated, broadband, tunable laser in the 700‐1100 nm spectral range. Typical sizes of the grown crystals are 25‐30 mm in diameter and 30‐40 mm in length. Symmetrical and sharp conoscopy pictures confirm the optical homogeneity of the crystals. Optical transmission was recorded for both undoped and doped crystals. 70% transmittance was observed. The grown crystals have reasonably good laser damage threshold. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
2.
The ferroelectric phase of potassium lithium niobate K3Li2−xNb5+xO15 (KLN) is a very promising material for the conversion of infrared light to light in the visible region. However, growing of single crystals is known to be complicated due to the considerable anisotropy of the growth rate and the thermal expansion behaviour. The single crystals of KLN, Mg2+‐doped KLN, as well as the mixed crystals of potassium lithium tantalate niobate K3Li2(Nb1−xTax)5O15 (KLTN) were grown by the Czochralski technique. The chemical analyses of the samples were performed by atomic absorption spectroscopy (AAS) and X‐ray fluorescence analysis (XRF). The element concentrations along the single crystals were measured by the electron microprobe analysis (EMPA) to clarify the segregation phenomena in the grown crystals. The elements distribution coefficients were also calculated. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
3.
The ferroelectric phase of potassium lithium niobate K3Li2–xNb5+xO15+2x (KLN) in the range of 0.15 < x < 0.5 is a very promising material for the second harmonic generation (SHG) in the blue visible region (∼410 nm). The ferroelectric phase transition was shown to occur between 400 and 500°C depending on the composition of the KLN phase. In this study several analysis techniques were used to investigate the phase transition on ferroelectric (x = 0.3) KLN samples. The temperature‐dependent measurements of the relative dielectric constant ε33 provided a phase transition temperature of about 470°C. In our DTA experiments, a small but reproducible thermal effect at the phase transition in KLN was indicated. The temperature‐dependent birefringence measurement technique, applied the first time on KLN, shows a second order behaviour at a temperature of 467 °C. However, this phase transition is accompanied by a small thermal effect. The DSC analysis for the other KLN composition (x = 0.5) provided a phase transition temperature of 514 °C. The appearance of a phase transition in the paraelectric KLN phase (Nb content higher than 55 mol%) was also studied. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
研究了高温富锂气氛下锂离子在低掺镁铌酸锂晶体中的扩散.采用气相输运平衡法制备了掺杂1mol; MgO的不同锂含量的铌酸锂(Mg1LN)晶体,采用热分析仪测试了晶体的居里温度.制备了一系列不同锂含量的Mg1LN多晶料,拟合了晶体锂含量与居里温度的关系.采用Boltzmann-Matano法求解了扩散方程.结果表明,扩散温度为1100 ℃时,Mg1LN晶体中锂离子扩散系数为3.2×10-9~13.0×10-9 cm2/s,当扩散温度为1145 ℃时锂离子扩散系数约是1100 ℃时扩散系数的三倍.因此,适当提高扩散温度是提高气相输运平衡法制备近化学计量比低掺镁铌酸锂晶体效率的有效办法. 相似文献
5.
L. Gao J. Y. Wang H. Liu X. B. Hu S. H. Yao J. B. Wu X. Y. Qin R. I. Boughton 《Crystal Research and Technology》2006,41(4):332-336
A near‐stoichiometric LiNbO3 single crystal has been grown by the Czochralski technique from a melt of 58.5 mol% Li2O. Its composition homogeneity was assessed by measuring the UV absorption edge. It was found that the maximum composition difference is about 0.03 mol% in the radial direction and 0.05 mol% in the axial direction. Differential scanning calorimetry (DSC) analysis was performed on the powder from the synthesized raw material and the frozen melt after crystal growth. The analytical results indicate that, during crystal growth, the magnitude of lithium volatilization from the melt surface is more than the degree of segregation from the crystal. The volatilized lithium diffuses into the crystal to compensate for the lithium segregation in the LiNbO3 crystal. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
Dmytro Sugak Ihor Syvorotka Uliana Yakhnevych Oleh Buryy Neonila Levintant‐Zayonts Hrygoriy Savytskyy Oleksandr Bonchyk Sergii Ubizskii 《Crystal Research and Technology》2019,54(12)
Spatial changes of optical and mechanical properties of doped lithium niobate (LN, LiNbO3) single crystals are investigated. The crystals are doped with copper ions by thermal diffusion at elevated temperatures. LiNbO3 crystal absorption spectra are recorded in a direction perpendicular to the direction of diffusion. The concentrations of copper ions are calculated using the Smakula–Dexter formula. To determine a relation between changes of optical and mechanical properties, the hardness profiles of the doped crystals are investigated by the nanoindentation technique. Young's modulus and hardness are specified in accordance with the Oliver–Pharr method. 相似文献
7.
铌酸锂是集电光、声光、压电和非线性等性能于一体的人工晶体,在光子学及光电子学等领域具有广泛的应用前景,被誉为“光学硅”或“光子学硅”。近年来随着基于薄膜铌酸锂的集成光子学的迅猛发展,铌酸锂晶体受到更加广泛的关注。然而铌酸锂是一种典型的非化学计量比晶体,其含有大量的本征缺陷,严重影响了晶体性能;同时,铌酸锂晶格对众多杂质离子都有良好的固溶性,而且晶体的性质随着杂质离子的种类和浓度不同产生显著变化。如同单晶硅等半导体材料的缺陷工程,缺陷已经并且必将继续对晶体的性能及铌酸锂集成光子学产生重要影响。本文对铌酸锂晶体的缺陷结构做了一个简要的回顾,尤其是近期涉及薄膜铌酸锂晶体的相关内容,涵盖了本征缺陷结构、非本征缺陷结构、缺陷结构的表征、缺陷结构的理论计算、缺陷结构与晶体性能的构效关系等方面,以期对当前的铌酸锂集成光子学研究贡献微薄之力。 相似文献
8.
A facile route to prepare lithium niobate (LiNbO3) powders was proposed by an alternative solid‐state method. Stoichiometric Li2C2O4 and ammonium niobium oxalate were mixed with small amounts of water and then dried at room temperature. It was demonstrated that Li[NbO(C2O4)2]·n H2O intermediate was produced by an ion‐exchange reaction. Pure LiNbO3 powders were successfully synthesized by heating the intermediate at 500, 600 and 700 °C for 3 h. X‐ray diffraction (XRD), scanning electron microscopy (SEM), Fourier‐transform infrared (FTIR) spectroscopy, UV‐Vis diffuse reflectance (UV‐Vis) spectroscopy and thermogravimetric (TG) analysis were used to characterize the precursor compound and as‐prepared samples. XRD results reveal that all the products are identified as hexagonal structure with high relative crystallinity (>87%). The particle size is found to be about 40 nm for the mixture calcined at 500 °C according to XRD data, which is in good agreement with SEM data. The as‐prepared LiNbO3 powders by this method are high quality according to FTIR spectra. (Li0.996Nb0.005)Nb0.999O3 phase was formed when the calcination temperature was raised to 800 °C. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
采用激光脉冲沉积与射频等离子体相结合的方法(PLD-RF),在蓝宝石衬底上一步沉积了掺氮铌酸锂(LiNbO3:N)薄膜.采用X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)和紫外-可见-红外光谱仪(UV-Vis-NIR)对LiNbO3:N的晶格结构、掺杂含量及价态、光学性质进行了研究.结果表明铌酸锂薄膜沿(006)方向择优生长,其中氮的原子含量为2.04;,替代氧原子的位置,N的掺入有效的窄化了LiNbO3的带隙,使其紫外-可见吸收光谱的吸收边出现红移,并且在铌酸锂禁带中引入了杂质能级(Ev),能级深度为2.7 eV. 相似文献
10.
I.V. Kityk M. Makowska‐Janusik M.D. Fontana M. Aillerie F. Abdi 《Crystal Research and Technology》2001,36(6):577-588
We present a band structure approach with a molecular dynamics cluster optimization which accounts for the various structural modifications related to the non‐stoichiometry of LiNbO3 crystals. The variation of the optical properties with the deviation from the stoichiometric composition can be understood within this approach. Particular role of the electron‐phonon contributions to the electrooptics coefficient is shown. Model calculations yield a large dependence of the electrooptis coefficient r22 on the crystal composition, in agreement with the experimental data. The observed minimum of the r22 coefficient versus the non‐stoichiometry is interpreted as originated from the non‐centrosymmetry in the electrostatic potential distribution around Nb‐O6 clusters. 相似文献
11.
近化学计量比掺镁铌酸锂晶体的抗光折变性能 总被引：3，自引：0，他引：3
应用气相传输平衡技术,我们获得了3种近化学计量比掺镁铌酸锂晶体,晶体的掺镁量接近我们以前提出的第二阈值.在我们实验室所能达到的最大光强26 MW/cm2照射下,在所有近化学计量比掺镁铌酸锂晶片中没有观察到光斑畸变,该光强比同成分铌酸锂晶体所能承受的光强高6个量级,为目前已报道的铌酸锂晶体之最.应用双光束全息写入法测得掺1.0 mol; Mg近化学计量比铌酸锂晶体的光折变饱和值仅有4.6×10-7,比同成分铌酸锂晶体小两个量级,从已有实验数据推测,该晶体的抗光折变能力应当比同成分铌酸锂晶体高9个量级以上. 相似文献
12.
B. Riscob Indranil Bhaumik S. Ganesamoorthy R. Bhatt N. Vijayan Khavangkhui Zimik A. K. Karnal G. Bhagavannarayana P. K. Gupta 《Journal of Applied Crystallography》2015,48(6):1753-1760
Single crystals of undoped and Ru‐doped congruent LiNbO3 (LN) were successfully grown by the Czochralski method. The axial and radial gradient of the radio frequency furnace was controlled in order to obtain crack‐free single crystals. Wafers were cut from the grown Ru‐doped single crystal at different axial positions along the growth direction and subjected to various characterization analyses. Good optical homogeneity and low residual strain in the grown crystal is confirmed by the conoscopy patterns. Further, it is confirmed that Ru doping does not influence the optical sign of the crystal. From a high‐resolution X‐ray diffractometry analysis, it is evident that the as‐grown undoped LN crystal exhibited better crystalline perfection with a single and sharp diffraction curve in comparison to the Ru‐doped crystals, which are characterized by a broader diffraction curve. Absorption coefficient and band‐gap analysis across the axial length revealed a concentration variation of Ru across the length. Refractive index measurements carried out using a prism coupler showed variation in the optical birefringence, also due to the variation of Ru concentration at different positions of the grown single crystal. 相似文献
13.
铌酸锂晶体的生长研究 总被引：3，自引：1，他引：2
近年来,铌酸锂晶体由于其自身所具有的多种优异性能和巨大的应用前景而受到了人们的广泛关注,但生长出满足不同市场要求的高质量铌酸锂单晶体比较困难.本文从晶体生长技术的角度综述了铌酸锂单晶体不同的生长方法以及各自的特点,并分析了在生长铌酸锂晶体时出现的一些问题. 相似文献
14.
6.0 mol. % ZnO doped LiNbO3 crystals were grown by Czochralski technique. Various Li/Nb mole ratios of 0.942, 0.970, 1.000, and 1.020 were used to prepare the starting materials. Second harmonic generation (SHG) experimental results show that the phase matching temperature increases near linearly with the increasing of Li/Nb ratio, and the SHG efficiency is enhanced by the Zn doping and the increasing of Li/Nb ratio. The intrinsic and extrinsic defects are discussed in this paper to explain the SHG behavior and photo‐damage resistance in the Zn doped Li‐rich LiNbO3 crystals. 相似文献
15.
铌酸锂晶体的缺陷及其控制 总被引：1，自引：0，他引：1
针对铌酸锂晶体中的缺陷研究,本文总结了国内外学者提出的不同晶体缺陷模型及各自的特点,并介绍了我们提出的铌位依赖、锂位敏感模型.在分析晶体缺陷研究的基础上提出了对铌酸锂晶体进行缺陷控制的意义及理论依据,指出缺陷控制的主要任务是保护锂格位.本文还简要概括了铌酸锂晶体缺陷控制的主要手段,并建议从反映铌酸锂晶体性能的角度来研究缺陷结构. 相似文献
16.
Mg:Mn:Fe:LiNbO3 crystals were grown by the Czochralski method. The defect structure was analyzed by UV‐vis spectra and IR spectra. The holographic storage of Mg:Mn:Fe:LiNbO3 crystals was measured by the two color fixed method. The results show that with the increase of MgO doping concentration, the writing time becomes shorter, the dynamic range decreases, photorefractive sensitivity increases and fixing diffraction efficiency decreases. When the MgO doping concentration exceeds 4.5 mol%, the fixing diffraction efficiency approaches zero. The effect of doping Mg ions on the holographic storage properties of Mn:Fe:LiNbO3 crystals is discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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18.
通过选择合适的原料配比(Li2O 48.6mol;,Nb2O5 51.4mol;),控制固液界面处的温度梯度为20～40℃/cm,晶体生长速度为0.6～1.5mm/h,采用密闭条件下的坩埚下降法工艺成功地生长出了具有良好光学均匀性的完整LiNbO3单晶.用X射线粉末衍射表征获得的LiNbO3晶相,讨论了若干工艺条件对晶体组分与质量的影响.测定了未密闭条件下生长的LiNbO3晶体不同部位样品的紫外可见光谱,发现其吸收边沿生长方向发生红移,并讨论了产生此现象的原因. 相似文献
19.