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1.
S. Selvakumar K. Rajarajan S. M. Ravi Kumar I. Vetha Potheher D. Prem Anand K. Ambujam P. Sagayaraj 《Crystal Research and Technology》2006,41(8):766-770
Metal (Cd2+ and Cu2+) substituted single crystals of Bis(thiourea) zinc chloride (BTZC) are grown by slow solvent evaporation technique, with the vision to improve the physicochemical properties of the sample. Single crystal XRD studies of both pure and doped samples are carried out and the results are compared. Optical absorption and FTIR studies are performed to identify the UV cut‐off range and the presence of various functional groups in the grown crystals. The thermogravimetric (TG) analysis of metal doped BTZC indicates a marginal increase in the thermal stability of the crystals. The dielectric response of the samples have been studied in the frequency range 100 Hz to 5 MHz at room temperature and the results are discussed. Photoconductivity studies carried out on pure and metal doped BTZC crystals revealed the negative photoconducting nature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
2.
G. P. Joseph I. Korah K. Raja Rajan P. C. Thomas M. Vimalan J. Madhavan P. Sagayaraj 《Crystal Research and Technology》2007,42(3):295-299
Good optical grade single crystals of pure, Cd2+ and Mg2+ doped Manganese Mercury Thiyocyanate (MMTC) crystals are grown by slow solvent evaporation technique at room temperature. Single crystal XRD studies reveal that the incorporation of metallic dopants has not changed the structure of the parent crystal. The SHG efficiencies of the pure and doped samples of MMTC are measured by Kurtz Perry powder method and the results are compared with urea. It is evident from microhardness study that the presence of dopants has increased the mechanical strength of MMTC crystal. The TG/DTG studies confirm that the thermal decomposition temperatures of pure (353°C), Mg2+ doped (363°C) and Cd2+ doped (365°C) MMTC are relatively high when compared to other NLO crystals of the same family. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
3.
The Er3+doped Mg:LiNbO3single crystal fibers employed in our experiment were grown in air by a micro‐pulling down (μ‐PD) method from host materials of a congruent Li/Nb (0.945) ratio which were melt‐doped with a nominal molar concentration of 1, 3, 5% MgO and 0.6% Er2O3. The X‐ray diffraction analysis results indicated that the co‐doped crystals main tained the same structural characteristics as the undoped LiNbO3, however the lattice parameters with Mg differed; c (Å) value decreased, and a (Å) increased than of pure LiNbO3. The influence of dopants on the photoluminescence (PL) properties of the Er:Mg:LiNbO3 single crystal fibers excited by laser lines of 514 nm was reported. Also, the PL properties according to temperature and the excitation power of Er:Mg:LiNbO3 crystal fibers were analyzed. 相似文献
4.
Single crystals of Mn2+ doped calcium levo‐ tartrate tetrahydrate (CLTT) were grown by single diffusion gel growth technique in silica hydro‐gel media. The doping of Mn2+ was varied by mixing 0.001M, 0.005M, 0.01M, 0.05M, and 0.1M solutions of MnCl2 with 1M CaCl2 solution in equal volumes in the supernatant solutions. The actual amount of Mn2+ doping in CLTT crystals was estimated by ICP (Inductively Coupled Plasma) technique. The powder XRD of the samples suggested no significant change in the unit cell dimensions and the presence of any extra phase. The FT‐IR spectra indicated the presence of water molecule, O‐H bond, C‐O bond and carbonyl C=O bond. The EPR spectra confirmed the presence of Mn2+ ions in the crystals. The variation of the dielectric constant with temperature confirmed the earlier results of pure calcium tartrate crystals and indicated the ferroelectric nature of the doped crystals. As the amount of doping of Mn2+ increased the value of dielectric constant increased. The results are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
Pure and Co‐doped Li2B4O7 (LBO) single crystals were grown by the Czochralski method. Starting concentrations of Co2O3 in the melt were: 0.5, 0.85 and 1 mol% relative to Li2CO3. Technological factors affecting the quality of both crystals were discussed. Optical absorption and EPR spectra were analyzed to define the oxidation states and lattice sites of cobalt ions. It was shown that Co2+ ions enter LBO crystal at octahedral Li+ site positions. Low‐temperature EPR measurements revealed that two types of Co2+ complexes can be distinguished in the Li2B4O7:Co crystals. Additional absorption calculated for γ‐irradiated crystals showed Vk type defects suggesting the creation of cation vacancies during growth. The concentration of the defects decreases with an increase of intentional Co concentration. Introduction of cobalt ions to LBO crystal is limited probably by the formation of cobalt ion pairs or by the entrance of cobalt as Co+. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
M. Gulam Mohamed M. Vimalan J. G. M. Jesudurai J. Madhavan P. Sagayaraj 《Crystal Research and Technology》2007,42(10):948-954
Single crystals of organic nonlinear optical material of pure, Cu2+ and Mg2+ doped L‐arginine acetate (LAA) were successfully grown by slow evaporation method at room temperature. The UV‐Vis‐NIR spectra of pure and doped LAA indicate that these crystals possess a wide optical transmission window from 240‐1600 nm. Non‐linear optical studies reveal that the SHG efficiency of LAA is nearly three times that of KDP. The dielectric response of the samples was studied in the frequency region 100 Hz to 2 MHz and the influence of Cu2+ and Mg2+ substitution on the dielectric behaviour had been investigated. Photoconductivity study proves that both pure and Cu2+ and Mg2+ doped LAA crystal exhibit positive photoconductivity. It is evident from the Vickers hardness study that the hardness of the crystal decreases with increasing load both for pure and doped samples. ESR studies confirmed the incorporation of Cu2+ into LAA and the value of g‐factor was found to be 2.1654. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
E. Giannini V. Garnier N. Clayton N. Musolino R. Gladyshevskii R. Flükiger 《Crystal Research and Technology》2004,39(10):926-931
Large and high‐quality single crystals of both Pb‐free and Pb‐doped high temperature superconducting compounds (Bi1‐xPbx)2Sr2Ca2Cu3O10‐y (x = 0 and 0.3) were grown by means of a newly developed “Vapour‐Assisted Travelling Floating Zone” technique (VA‐TSFZ). This modified zone‐melting technique was realised in an image furnace and allowed for the first time to grow Pb‐doped crystals by compensating for the Pb losses occurring at high temperature. Crystals up to 3×2×0.1 mm3 were successfully grown. Post‐annealing under high pressure of O2 (up to 10 MPa at T = 500°C) was undertaken to enhance Tc and improve the homogeneity of the crystals. Structural characterisation was performed by single‐crystal X‐ray diffraction (XRD) and the structure of the 3‐layer Bi‐based superconducting compound was refined for the first time. Structure refinement showed an incommensurate superlattice in the Pb‐free crystals. The space group is orthorhombic, A2aa, with cell parameters a = 27.105(4) Å, b = 5.4133(6) Å and c = 37.009(7) Å. Superconducting studies were carried out by A.C. and D.C. magnetic measurements. Very sharp superconducting transitions were obtained in both kinds of crystals (ΔTc ≤ 1 K). In optimally doped Pb‐free crystals, critical temperatures up to 111 K were measured. Magnetic critical current densities of 2�105 A/cm2 were measured at T = 30 K and μ0H = 0 T. A weak second peak in the magnetisation loops was observed in the temperature range 40‐50 K above which the vortex lattice becomes entangled. We have measured a portion of the irreversibility line (0.1‐5 Tesla) and fitted the expression for the melting of a vortex glass in a 2D fluctuation regime to the experimental data. Measurements of the lower critical field allowed to obtain the dependence of the penetration depth on temperature: the linear dependence of λ(T) for T < 30 K is consistent with d‐wave superconductivity in Bi‐2223. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
J.B. Shim N. Yoshimoto M. Yoshizawa D.H. Yoon 《Crystal Research and Technology》2001,36(11):1209-1214
Erbium (Er3+) doped LiNbO3 single crystal thin films have been grown LiNbO3 (001) substrate by the liquid phase epitaxy method. The crystallinity was determined by high‐resolution X‐ray diffraction. The lattice mismatch between Er3+ doped LiNbO3 films and LiNbO3 (001) substrate was investigated by X‐ray rocking curve analysis. Also we studied the structural characteristics of Er3+ doped LiNbO3 films and surface morphology dependent on the film thickness. 相似文献
9.
L. Malicsk L. Pogny A. L. Tth V. Horvth E. Beregi 《Crystal Research and Technology》2009,44(4):425-432
The as‐grown surface and inner structures of undoped and Nd3+‐, Cr3+‐, V3+‐, Ce3+‐, Er3+ and Yb3+ – and (Er3+ + Yb3+) – doped yttrium aluminum borate (YAB) single crystals grown from (K2Mo3O10 + B2O3) flux by spontaneous crystallization or top seeded solution growth (TSSG) technique, were investigated using optical and scanning electron microscopic and analytic chemical methods. Fine and rough growth hillocks of dislocational origin, growth layers, traces of inner planar defects and foreign phase crystalline debris were found and analyzed on the as‐grown faces of crystals. Irregular grains and regular block structures and foreign phase inclusions were observed and studied in the interior of the crystals. The chemical compositions measured by energy dispersive X‐ray spectrometry on perfect and imperfect micro regions are compared with those obtained by flame atomic absorption spectrometry on bulk crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
E. Talik M. Szubka D. Skrzypek W. Zarek J. Kusz T. ukasiewicz 《Crystal Research and Technology》2009,44(8):823-833
Single crystals of garnet Y3Al5O12 (YAG): Co and Co, Si were grown by Czochralski method as materials for optoelectronic applications. Silicon doping is responsible for the change of the Co3+ ions into Co2+ in order to keep charge neutrality of the material and for a coloration of materials. Magnetization and Electron Paramagnetic Resonance measurements show that the most cobalt ions in the silicon co‐doped crystals were Co2+ in octahedral positions. Estimated concentration of the Co2+ ions were close to Si4+ nominal concentration. A little excess of Co2+ may be ascribed to defects present in the crystals. For the crystal doped only with Co, the concentration of Co2+ was about 13% of the nominal Co amount and might be caused by crystal defects. X‐ray Photoelectron Spectroscopy measurements exhibit aluminium deficiency. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
Haiping Xia Xianlin Zeng Jinhao Wang Jianli Zhang Jian Xu Yuepin Zhang Qiuhua Nie 《Crystal Research and Technology》2004,39(4):337-342
The optical absorption spectra of LiNbO3 (LN), Fe:LiNbO3 (Fe:LN), and Zn:Fe:LiNbO3 (Zn:Fe:LN) single crystals grown by Bridgman method were measured and compared. The absorption characteristics of the samples and the effects of growth process conditions on the absorption spectra were investigated. The Fe, Zn and Li concentrations in the crystals were analyzed by inductively coupled plasma (ICP) spectrometry. The results indicated that the overall Fe ion and Fe2+ concentration in Fe:LN and Zn:Fe:LN crystals increased along the growing direction. The incorporation of ZnO in Fe:LN crystal induced increase of Fe2+ in the crystal. Among Fe‐doped and Zn:Fe‐codoped LN single crystals, 3 mol% ZnO doped Fe:LN had a biggest change of Fe2+ ion concentration from bottom to top part of crystal. The effects of technical conditions (atmosphere and thermal history) on Fe2+ ion concentration were discussed. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
12.
Crystals of ammonium tetrachlorozincate (AZC) undoped and doped with Sr2+ or Mn2+ in different concentrations were grown by the slow evaporation method from an aqueous solution. The crystal morphology changed considerably by doping. The dopant concentration in the crystals was measured by the atomic absorption technique. Slight changes in the unit cell parameters of AZC after doping with Sr2+‐ or Mn2+ have been detected. Optical absorption measurements indicated strong influence of Sr2+ and Mn2+ doping. The optical energy gap at room temperature decreased continuously with increasing Sr2+ and Mn2+ concentration but with two different rates. The dc conductivity was also measured as a function of temperature for the undoped and two samples doped with 0.144 Sr2+ and 0.191 Mn2+ and the results were compared. Positions possibly occupied by Sr2+ and Mn2+ cations in AZC lattice have been identified. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
P. Nisha Santha Kumari M. Beatrice Margaret S. Kalainathan 《Crystal Research and Technology》2009,44(2):177-183
Pure and potassium doped cadmium mercury thiocyanate single crystals have been obtained from silica gel by the process of diffusion. The X‐ray diffraction studies reveal the crystal lattice of both pure and doped crystals to be tetragonal. The crystalline perfection of the grown crystals were investigated by high resolution X‐ray diffraction analysis and the quality of the crystals are found to be extremely good. Transmission and Fourier transform infrared spectra were recorded for the grown crystals. The TG/DTA analyses show that the crystals are highly thermally stable. The mechanical strength of the crystals were studied by Vickers microhardness test and a study of their second harmonic generation efficiency in comparison with urea has been made by performing Kurtz powder test. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
P. Solarz M. Nikl A. Kos R. Lisiecki W. Ryba‐Romanowski A. Rzepka S. Ganschow A. Pajczkowska 《Crystal Research and Technology》2007,42(12):1308-1313
Single crystals of GdCa4O(BO3)3 (GdCOB) pure and doped with Eu concentration of 1 and 4 at% were grown by the Czochralski and micropulling‐down methods. The distribution of Eu ions in GdCOB crystals was uniform. The substitutions of Eu3+ in Gd, Ca(1) and Ca(2) cation sites and eventually formation Eu2+ have been investigated. The spectroscopic properties of crystals are compared with the properties of nanopowders obtained by sol‐gel method. Radioluminescence spectra of undoped GdCOB crystal show the characteristic emission of Gd3+ at about 312 nm, whereas this emission dramatically decreases in Eu‐doped crystals upon X‐ray excitation, as well as in Eu‐doped nanopowders excited in vacuum ultraviolet (VUV) region. The VUV excitation in the range 125‐333 nm for Eu‐doped samples leads to strong emission in red coming from the 5D0 multiplet of Eu3+, only. In the photoluminescence decay kinetics of 312 nm emissions substantial shortening and departure for single exponential decay in Eu‐doped samples is clearly observed. Higher Eu doping results in further acceleration of the decay. In undoped GdCOB crystal, the lifetime of the Gd3+ 6P7/2 multiplet is 2.79 ms. The Eu3+ 5D0 decay kinetics monitored at 613 nm are rather constant. Numerical fitting of fully exponential curves, reveals lifetimes 2.7 ms for nanopowder and 2.5 ms for single crystal. The results suggest that this material may be used as a red phosphor in plasma display panels in nanopowder form because of strong excitation band of Eu3+ luminescence in the 160‐200 nm regions. Contrary to nanopowder sample, such an excitation band, attributed to the Gd3+–O2– charge transfer was not observed in crystal obtained by the micropulling‐down method. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
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
16.
Guozong Zheng Genbo Su Xinxin Zhuang Xiuqin Lin Zhengdong Li 《Crystal Research and Technology》2008,43(8):811-816
KDP crystals were rapidly grown from solution doped with different Ba2+ concentrations. The effects of Ba2+ on the growth rate, morphology and quality of KDP crystals were discussed. Significant changes in shapes and volume of the grown crystals have been observed. During the growth process, defect region expands gradually with the increasing Ba2+ concentration. Samples were cut from different parts of the as‐grown crystals for investigating the optical quality, including transmission spectrum, scattering centers. Through comparison, it is found that the nonuniform distribution of Ba2+ ions causes remarkable difference in optical quality between prismatic and pyramidal sectors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
17.
T. I. Milenov P. M. Rafailov M. V. Abrashev R. P. Nikolova R. Titorenkova M. M. Gospodinov 《Crystal Research and Technology》2009,44(11):1192-1196
Large crystals of La0.63Pb0.37Mn O3+δ with small La(Pb)‐ deficiency of about 0.005‐0.01 at.% were grown by high temperature solution growth method. The structure of the grown crystals was determined as rhombohedral with R‐3 space group by single‐crystal X‐ray diffractometry. The surface morphology of the crystals and the exact chemical composition was examined by scanning electron microscopy and energy dispersive X‐ray analysis methods, respectively. The IR‐transmission spectrum reveals the presence of Mn3+O6‐ and Mn4+O6‐ octahedra in the lattice of La0.63Pb0.37Mn O3+δ crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
18.
The changes of lattice parameter and colour centre concentration are examined in KCI crystals (both pure and Me2+-doped) irradiated by γ-rays at room temperature. For the pure crystals the relative volume change vs. F-centre concentration plot reveals the presence of two stages, one ascribed to the introduction of colour centre pairs (or F centres only) and other to the generation of the new dislocations (or new dislocations with trapped-hole centres). In Me2+ doped crystals the lattice expansion bears a complex character (in the initial irradiation stage a transient maximum appears). Additional anomaly appears in Eu2+ KCI in the high-dose range where in spite of a distinct F-centre concentration drop a marked raise of the lattice parameter is observed. 相似文献
19.
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
20.
Mn substituted ZnO nanocrystals synthesized by a co‐precipitation method. X‐ray diffraction (XRD) studies confirms the presence of wurtzite (hexagonal) crystal structure similar to un doped ZnO, suggesting that doped Mn ions go at the regular Zn sites. The lattice parameters a and c are increasing with increasing Mn content. The unit cell volume increases with increasing Mn concentration, indicating the homogeneous substitution of Mn2+ for the Zn2+. The lattice distortion parameter (εv) is evaluated from XRD data and found that it enhances as Mn content increases. Transmission electron microscopy photographs show that the size of the ZnO crystals is in the range of 20‐50 nm. The SAED pattern confirms the hexagonal and crystalline nature of the samples which are in agreement with X‐ray analysis. The chemical groups of the samples have been identified by FTIR studies (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献