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waiy2001(金币+1,VIP+0):牛， 9-19 22:36
xiaojun111(金币+1,VIP+0):小弟在此谢了，希望以后多多交流 9-23 10:42
原文链接：http://www.cdgdc.edu.cn/yxbslw/pxjg/2005/abstract/wangxinqiang.htm
作者姓名：王新强
论文题目：双金属硫氰酸盐配合物晶体的生长和性质研究
作者简介：王新强，男， 1971年01月出生，1999年09月师从于山东大学许东教授，于2002年06月获博士学位。
中 文 摘 要
本论文在系统研究非线性光学晶体，发现可实现半导体激光直接倍频获得大于10毫瓦紫光输出的硫氰酸镉锌(ZnCd(SCN)4，简称ZCTC) 和硫氰酸汞镉(CdHg(SCN)4，简称CMTC)晶体的基础上，设计、合成并生长了一批具有ABTC(分子式为AB(SCN)4)与ABTL(AB(SCN)4Ln)型的双金属硫氰酸盐配合物晶体，完成其结构和性能测定，研究其组成、结构和性能之间的规律性。
1.本文系统地研究了四种结构类型为ABTC的双金属硫氰酸盐配合物：ZCTC、硫氰酸汞锌(ZnHg(SCN)4， 简称 ZMTC)、CMTC和硫氰酸汞锰（MnHg(SCN)4， 简称 MMTC）四种非线性光学晶体合成、生长、结构及性能。
用A和B的氯化物、硝酸盐和醋酸盐以及钾、钠、铵的硫氰酸盐作为原料，合成了AB(SCN)4，以自发成核获得完整的小单晶作籽晶，通过蒸发法或降温法可得到较好单晶。
四种晶体均属于四方晶系，空间群为I ， Z=2。在 ABTC 晶体结构中，分别以 A、B 为核形成AN4、 BS4 两个配位四面体单元，以 –A-NCS-B– 为链在空间形成无限的三维网络结构。从红外光谱可以看出，与以自由(SCN)-形式存在的KSCN相比，四种配合物n(CN)和n(CS)伸缩振动波数有较大的紫移，而d(SCN)则有较大的红移。这充分说明了金属已与硫氰根的N和S原子配位。根据四种配合物的粉末衍射和TREOR指标化程序所的结构数据与四圆单晶数据非常吻合。它们的分解温度分别为234，173， 203 和 289 °C。
ZCTC、ZMTC、CMTC 和MMTC 晶体粉末的SHG 效率至少比尿素高一个量级，其中ZCTC的SHG 效率为尿素的51.6倍。ZCTC、CMTC 和MMTC 晶体的截止波长分别为290，372和373 nm。CMTC和MMTC的截止波长基本一样，分别较ZCTC晶体红移了82和83 nm。 在400~500 nm 之间，MMTC晶体有两个吸收峰(432，453 nm)，这是由Mn2+的电子d-d跃迁造成的。n→π* 跃迁中 S 原子上的 n 电子到共轭体系中的 π* 的跃迁决定着紫外截止波长。在ZCTC晶体中，用不易亲硫的镉取代了亲硫的汞，削弱了晶体中阴阳离子的相互作用，使S上的n 电子不易发生n→π* 跃迁，进而使晶体的吸收边较其它晶体有较大紫移。
在室温和常压下，ABTC的生长溶液可以保持稳定的平衡状态。硫氰酸(HSCN)在空气中非常不稳定，极易分解。其盐相对较为稳定。尽管ABTC的水溶液在通常情况下可以保持稳定的状态，然而在较高温度下，它们的水溶液容易分解和水解。各种化学平衡的存在给生长溶液中带来了许多的杂质，这就给其晶体生长带来了一定困难，另外，原料中，高价杂质阳离子如Al3+, Fe3+, Co2+, Ni2+, Cu2+ 等的存在，也将影响整个生长过程。这些杂质的存在，严重影响晶体质量，尤其是其透过性能。通过选择合适的生长条件，基本上抑制了副反应的发生，同时选用纯度高的原料，为获得较为完美的晶体创造了条件。
利用群论分析了ABTC型配合物的拉曼光谱。以ZCTC和CMTC两种晶体为例，采用拉曼光谱和分子轨道理论探讨了ABTC具有非线性光学效应的原因。零波矢处喇曼活性和红外活性光学声子模为Gvib= 19A(R)+20B(R,IR)+ 21E(R,IR)。理论上可观测到81个拉曼峰。四种晶体的拉曼光谱有四个波数范围：100cm-1波数以下，晶格振动模式；100-300cm-1，以两种金属为中心的振动波段；300-1200cm-1，SCN内部的振动模式；2100-2200cm-1，CN伸缩振动模式。ZnCd(SCN)4中，SCN，ZnN4，CdS4，Zn(NCS)4，Cd(SCN)4和Zn2Cd2(SCN)8 簇的线性极化率比值分别为1.002, 1.022, 1.195，1.654, 1.609和1.479。而CdHg(SCN)4中，SCN，CdN4，HgS4，Cd(NCS)4，Hg(SCN)4和Cd2Hg2(SCN)8 簇的线性极化率比值分别为 1.002, 1.009, 1.564，1.933, 2.053和1.981。A(NCS)4 和 B(SCN)4 畸变四面体以及连接它们的电荷转移共轭桥-A-N=C=S-B-是该类晶体具有优良非线性光学性质的主要原因。
2.本论文进行了ZCTC晶体生长研究，获得尺寸为23 ´ 12 ´14 mm3单晶。该晶体生长过程中容易显露的面有柱面{100} 和 锥面{301}，一些小面如 {110}，{310}和 {101}有时也出现。详细研究了ZCTC晶体在 [100] 和 [001] 两个通光方向上的透过光谱。截止波长为290nm。垂直于(100)面的透过率远远高于沿(001)面的。其中，垂直于(100)面的透过率在330-2280nm波段高于70%；在标准紫光波长404nm和380nm的透过率分别为74.16和73.22%。
ZCTC晶体的在300K时比热为367.9 J.mol-1.K-1；热膨胀系数为a1=-1.69´10-5, a3=1.95´10-4/K；抗光损伤阈值为6.24GW/cm2；介电常数 εa=7.3，εc =7.8；直流电导率为 ρa=4.6´1010Ω.cm，ρc =1.4´1011Ω.cm。压电应变常数分别为d31=1.5，d36=9.5，d14=1.6，d15=15.3´10-12 C/N；电光系数分别为g51=1.7, g41=1.3, g13=0.40, g63=0.94´10-12 m/V。
研究了ZCTC晶体在生长过程中溶液包裹物、负晶、开裂、生长条纹、扇形界及直线管道等宏观缺陷的形成。讨论了消除或抑制ZCTC晶体中缺陷产生的措施。
ZCTC晶体具有较大的比热和较高的抗光伤阈值。它的热膨胀系数具有很大的各向异性。ZCTC晶体拥有较高的倍频效率，较短的截止波长和较宽的透光波段。因而，ZCTC晶体是一种非常重要的蓝紫光非线性光学材料。同时，ZCTC晶体的压电应变常数d36和d15比较大一些。作为电光调制器，可用的电光系数γ13和γ63，ZCTC晶体的比较小。由于ZCTC晶体是一种配合物材料，其特殊的结构和生长机理，极易产生象包裹物、开裂、生长条纹等宏观缺陷，严重影响晶体的完整性及光学性能，限制其使用，因此我们首次分析了该晶体中的宏观缺陷及其成因。今后将继续研究其微观缺陷，提出其减少和抑制缺陷的措施。为制造优质光学器件提供优质单晶。
3.报道了用恒温蒸发法和降温法生长出了MMTC单晶，最大尺寸为18´13´12 mm3。研究了它的性能。该晶体生长过程中容易显露的面有柱面{110} 和 锥面{211}，一些小面如 {100} 和 {101}有时也出现。它的分解温度为286°C, MMTC晶体的紫外截止波长为373nm，在330K时的比热为468.1 J/mol/K， 晶体沿a-和c-向的热膨胀系数分别为 -1.06 ´ 10-5 和1.44´ 10-4 K-1。
MMTC晶体的透光性尽管不如ZCTC晶体，比CMTC也稍差点，但是MMTC晶体的热稳定性优于ZCTC和CMTC晶体，MMTC晶体的粉末倍频转换效率优于CMTC晶体，因此MMTC晶体可以成为非线性光学的候选材料。
4.为了深入研究探讨双金属硫氰酸盐的组成、结构与性能之间的规律，本文合成、制备了三种全新的结构类型为ABTL的MMTC的路易斯碱衍生物非线性光学晶体：二二甲亚砜合硫氰酸汞锰(简称MMTD)，乙二醇一甲醚合硫氰酸汞锰(简称MMTG)，二水合二N,N-二甲基乙酰胺合硫氰酸汞锰(简称MMTWD)。
用四圆衍射仪测定了MMTD，MMTG和MMTWD晶体的空间群分别为P212121，Pca21和P 。通过降温法获得尺寸分别为25 ´ 18 ´ 18，34 ´ 23 ´ 18和17 ´ 17 ´ 6 mm3的单晶。MMTD，MMTG和MMTWD晶体生长过程中容易显露的面分别为{001}、{112}、{113}、{101}和{011}；{010}、{100}和{201}；{001}、{010}、{100}和{201}。其粉末倍频效率分别为尿素的23倍，尿素的1倍和KDP的1倍，紫外截止波长分别为375，375和360 nm，透光波段分别为375-2560、375-2265和360-1790 nm。它们的分解温度分别为145，145和70˚C。并对MMTD和MMTWD两种晶体的比热和热膨胀性能进行研究。
这三种晶体具有较高的粉末倍频效率，截止波长伸向紫外，并有较宽的透光波段。因此它们可能成为非线性光学晶体的候选材料。
关键词：双金属硫氰酸盐，金属配合物单晶，光电功能晶体材料，单晶生长，晶体结构与性能
Investigation on crystal growth and properties of bimetallic thiocyanate coordinationcomplex crystals
Wang Xinqiang
ABSTRACT
Lately, over 10 mW violet 404nm radiation has been generated by type-I single-pass frequency doubling of the output of an diode laser in critically phase-matched ZnCd(SCN)4(ZCTC) crystal. In this article, a series of bimetallic thiocyanate complexe crystals with the ABTC (the abbreviation for (AB(SCN)4) and ABTL (AB(SCN)4Ln) structure type have been designed and prepared on the basis of investigation of nonlinear optical crystals. Their structures have been determined and their performances have been characterized. The regularities among the composition, structure and performace have also been discussed.
1. The preparation, crystal growth, structure and performance of four bimetallic thiocyanates with the ABTC structure type: ZCTC, zinc mercury thiocyanate (ZnHg(SCN)4, abbreviated as ZMTC), cadmium mercury thiocyanate (CdHg(SCN)4, abbreviated as CMTC) and manganese mercury thiocyanate (MnHg(SCN)4, abbreviated as MMTC) are investigated systematacially.
AB(SCN)4 have been prepared by using AX2(A = Zn, Cd or Mn, B= Cd or Hg, X = NO3, Cl or CH3COO) and MSCN(K, Na, NH4). Using the small single crystals obtained as deeds, high-quality and considerably large single crystals can be obtained by solvent evaporation or temperature lowering of such supersaturated solutions.
The crystals belong to tetragonal crystallographic system with space group I , Z=2. In ABTC crystal structures, the -N=C=S- bridges which connect the central atoms of the flattened tetrahedra, A and B which are located at the center of the fourfold inversion axis, forming inifinite three-dimensional -A-N=C=S-B- networks. From the IR spectra, one can see that the sharp increase in wavenumbers of nCN stretching and nCS stretching and decrease in that of dSCN bending in the four compounds compared with the corresponding bands in the free thiocyanate radical of KSCN. This confirms the metal-nitrogen and metal-sulfur coordination in the structures. The structural data, obtained by the X-ray powder diffraction pattern and TREOR program, agree well with the results determined by an R3m/E four-circle X-ray diffractometer. Their decomposition temperatures are 234，173，203 and 289 °C, respectively.
The powder SHG efficiencies of ZCTC, ZMTC, CMTC and MMTC are all over one order of magnitude higher than that of Urea. Among them, the SHG efficiency of ZCTC is 51.6 times that of Urea. The cutoff wavelengths of ZCTC, CMTC and MMTC are 290, 372 and 373 nm, respectively. In the range of 400-500 nm, two sharp absorption lines are observed for MMTC crystal due to the d-d transitions present in the 4d orbits of Mn2+ ions. The n®p* transitions of the n electrons on the S atom to the lowest anti-bonding p* of the conjugated system may be the determinant of the cutoff wavelength. Since the softer cation Hg2+ shows a more pronounced affinity for coordination with the softer ligand S (SCN) than the harder cation Cd2+. Therefore, the UV cutoff of ZCTC crystal should be hypsochromic shift compared with the other crystals.
At room temperature and normal atmosphere, the growth solutions can keep equilibrium states. Thiocyanic acid (HSCN) is much more unstable than its thiocyanates, which is easy to decompose. Although the aqueous solution of ABTC can retain in stable state without decomposition and hydrolysis at atmospheric pressure and relatively low temperature for a long time, whose aqueous solution will be decomposed and hydrosised if it is kept at high temperature for several days. Several foreign metallic cations, such as Al3+, Fe3+, Co2+, Ni2+, Cu2+ and etc. will affect the whole growth process. Their effects are related with ionic radii, electric charge, complex formation in the bulk and at the surface, and frequency of solvent exchange. The presence of these impurities will badly influence the quality of ABTC crystals, especially their transparency. By selecting suitable growth conductions, the by-reactions are limted, and at the same time, high-purity starting materials are used, the high-optical-quality can be obtained.
The Raman spectra of the four complexes are analyzed by using group theory. Taking ZCTC and CMTC as samples, the reasons of the high optical nonlinearities of ABTC crystals have been studied by the use of the Raman spectra and the Molecular Orbital (MO) theory. The Raman(R)- and infrared (IR)-active optical phonon modes at zero wave vector are Gvib = 19A(R) + 20B(R, IR) + 21E(R, IR). Theoretically, the observable Raman peaks are no more than 81.The Raman spectra of the four crystals comprise four wavenumber regions: below 100 cm-1, lattice vibration modes; 100-300cm-1, vibration bands of the two metal centers; 300-1200cm-1, SCN internal vibration modes; 2100-2200cm-1, CN stretching vibration modes. The anisotropy of SCN, ZnN4, CdS4, Zn(NCS)4, Cd(SCN)4, and Zn2Cd2(SCN)8 clusters in ZCTC is 1.002, 1.022, 1.195, 1.654, 1.609, and 1.479, respectively, and the anisotropy of SCN, CdN4, HgS4, Cd(NCS)4, Hg(SCN)4 and Cd2Hg2(SCN)8 clusters in CMTC is 1.002, 1.009, 1.564, 1.933, 2.053 and 1.981. Therefore, the high optical nonlinearities of the crystals are chiefly ascribed to the distorted A(NCS)4 and B(SCN)4 tetrahedra and the conjugated charge-transfer (–A–NCS–B–) bridges that connect all the distorted tetrahedra together.
2. Single crystal growth of ZCTC crystal is carried out emphatically. Large single crystals with dimensions of 23 ´ 12 ´14 mm3 have been grown from aqueous solutions by the solvent evaporation method. The crystal exhibits the typical crystal habit formed by a tetragonal prism with {100} facets and a tetragonal disphenoid with {301} facets. In addition to the major {100} and {301}facets, some small facets, such as {110}, {310} and {101} are present sometimes. The transmission spectra of ZCTC are studied in detail. The UV cutoff wavelengths are the same along the [100] and [001] directions, which indicate that the UV cutoff wavelength of ZCTC crystal is 290 nm. The transmission normal to (100) plane is superior to that normal to (001) plane. In the transmission normal to (100) plane, the average transmittance of 70% in the transmission band between 330 and 2280 nm, and the transparent percentage at standard violet light of 404 nm and 380 nm are 74.16% and 73.22%.
The specific heat of the crystal is 367.9 J/mol.K at 300 K. The thermal expansion coefficients, a- and c-oriented is -1.69 ´ 10-5 and 1.95 ´ 10-4 K-1, respectively. The optical damage threshold is about 6.24 GW/cm2. The dielectric constants of ZCTC crystal at 1 kHz are e11=7.3, e33=7.8. The direct current resistivities of ZCTC are ra=4.6´1010, rc= 1.4´1011W.cm. Its piezoelectric strain constants are d31=1.5, d36=9.5, d14=1.6, d15=15.3´10-12 C/N; and its electro-optic coefficients are g51=1.7, g41=1.3, g13=0.40, g63=0.94´10-12 m/V, respectively.
Six kinds of macro-defects have been found in ZCTC large crystals. These defects include: (1) crack, (2) inclusion, (3) negative crystal, (4) growth striation, (5) sector boundary and (6) straight pipe. The formation mechanisms and the methods of eliminating these defects are discussed.
ZCTC crystal exhibits a relatively large specific heat and large anisotropy in thermal expansion. The SHG efficiencies of ZCTC crystal powders are very high, and it has short UV cut off and wide transparent wavelength regime. The UV light output by direct laser-diode frequency doubling using ZCTC crystal was realized at room temperature through preliminary experiments. Therefore, ZCTC crystal is a promising material used in the blue-violet region for laser diode frequency doubling. Two of the piezoelectric strain constants: d36 and d15 are large and show promise in device applications. The electro-optic coefficients g63 and g13 of ZCTC crystal maybe used in electro-optic modulator. However, these electro-optic coefficients of ZCTC crystal are small. ZCTC crystal is a coordination complex material. The special structure and growth mechanism may produce several macro-defects which have a strong impact on the integrality and optical performance and limit its application. Therefore, the formation mechanisms and the methods of eliminating these defects are analyzed. For the future, the micro-defects of ZCTC crystal will be investigated and the methods of decreasing even eliminating the defects will be provided, so that high quality single crystals can be grown and the good optical devices can be prepared.
3. Solvent evaporation method and temperature-lowering method have been used to grow MMTC single crystals. Large single crystals with dimensions of 18´13´12 mm3 have been obtained. The properties of the as-grown crystals are studied. The crystal exhibits the typical crystal habit formed by a tetragonal prism with {110} facets and a tetragonal disphenoid with {211} facets. In addition to the major {110} and {211}facets, some small facets, such as {100}, {101} are present sometimes. The decomposition temperature of MMTC crystal is 289˚C, and the optical cut off wavelength is 373 nm. The specific heat of the crystal is 468.1 J/mol.K at 330 K. The thermal expansion coefficients, a- and c-oriented, have been measured to be -1.06 ´ 10-5 and 1.44 ´ 10-4 K-1, respectively.
The transparency performance of MMTC crystal is inferior to that of ZCTC crystal, also not better than CMTC. However, its thermal stability is superior to ZCTC and CMTC crystal, and the powder SHG efficiency is higher that of CMTC. Therefore, MMTC can be a potential material used in nonlinear optics.
4. In order to further investigate the relationship among the composition, structure and property of bimetallic thiocyanates, three novel nonlinear optical crystals: Lewis base derivatives of MMTC crystal with the ABTL structure type have been prepared: manganese mercury thiocyanate-bis(dimethyl sulfoxide)(abbreviated as MMTD), manganese mercury glycol monomethyl ether (abbreviated as MMTG) and diaqua(thiocyanato) manganese mercury-N,N-dimethylacetamide(abbreviated as MMTWD).
The crystal structures of the three crystals are determined by using a four-circle diffractometer. The space group of MMTD, MMTG and MMTWD crystal is P21 21 21 Pca21 and P , respectively. Single crystals of the three crystals with dimensions of 25 ´ 18 ´ 18, 34 ´ 23 ´ 18 and 17 ´ 17 ´ 6 mm3, respectively, have been grown out by using temperature-lowering method. MMTD, MMTG and MMTWD crystals exhibit {001}, {112}, {113}, {101} and {011}; {010}, {100} and {201}; {001}, {010}, {100} and {201} facets. The powder SHG efficiency of MMTD, MMTG and MMTWD is 23 times that of Urea, 1 time that of Urea and 1 time that of potassium dihydrogen phosphate(KDP), respectively. The UV optical cut-off wavelength of MMTD, MMTG and MMTWD is 375, 375 and 360 nm, and the transparency waveband is 375-2560, 375-2265 and 1790 nm, respectively. Their decomposition temperature is 145, 145 and 70˚C, respectively. The special heat and thermal expansion coefficients of MMTD and MMTWD crystals have also been studied.
The powder second harmonic efficiencies of the three crystals are high. They possess high powder SHG efficiencies, short UV cutoffs and wide transparency wavelength regime. Therefore, they are potential nonlinear optical candidates.
Keywords: Bimetallic thiocyanate, single crystals of metal complex, photoelectric crystal materials, single crystal growth, crystal structure and performance
[ Last edited by lijianghua2007 on 2009-9-19 at 19:49 ] |
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