Growth of CaMoO4 and SrMoO4 crystals in silica gel media

Growth kinetics and characterization of calcium and strontium molybdate crystals grown in silica gel have been studied under a variety of parameters. The changes in nucleation characteristics, growth habit, quality of these crystals were carefully observed and are found directly related to pH of the medium. The profound influence of pH on spontaneous crystallization of CaMoO₄ crystals has been carefully investigated; and its crystallization range has been determined. The wide morphological change of SrMoO₄ with respect to pH variation has been studied. The quality of the crystals has been critically examined.     

Growth,Structural and Microtopographical Studies of Calcium Iodate,Monohydrate Crystals Grown in Silica Gel

Single crystals of calcium iodate, monohydrate [Ca(IO₃)₂, H₂O] have been grown by gel technique. Prismatic, prismatic pyramidal, needle shaped and hopper crystals were obtained. These crystals were also grown by doping impurities such as copper and iron. Kinetics of growth parameters was investigated. Structural analysis was carried out by using X‐ray powder diffraction method. Microtopographical study of the habit faces, such as prismatic and pyramidal, of as grown crystals was carried out. Some surface structures are reported. These crystals were etched by various etchants and appropriate etchant is reported.     

Growth kinetics,habit modifications and surface designs of lead iodide grown by the new gel technique

Lead iodide crystals have been grown in silica gel by the new gel technique by the inter action between colloidal lead tartrate and KI solution. The crystals are found to exhibit interesting surface designs. Growth kinetics and habit modifications of the crystal have been investigated. Two dimensional surface nucleation and screw dislocation are found to partake in the growth process of the crystals.     

On the influence on tracht and habit of urea crystals (II)

It is shown that during crystallization urea forms mixed crystals, adsorption mixed crystals, and epitaxial growth from aqueous solutions with inorganic salts, the lattice parameters of which are lying within the tolerance of efficiency parameters of urea. The extent of the formation of mixed crystals is determined by the composition of the solution. The slats added to the solution affect changes of tracht and habit of urea and thus are important for improving storage and transport properties. Similar results can be found for modified melts of urea.     

Growth of different habits of lead bromide crystals in silica gel by the new gel technique

Lead bromide crystals of high optical perfection and of different habits have been grown in silica gel by new gel technique starting from colloidal lead tartrate and KBr solution. pH is found to be not a factor for habit modification. Certain habits of the grown crystals exhibit interesting surface features. The growth conditions have been optimized and the various aspects of the growth process have been widely investigated.     

The influence of supersaturation on crystal morphology – experimental and theoretical study

The surface docking approach of molecular modeling for prediction of crystal morphology in the presence of additives is further developed in this work. It is modified in order to take into account the influence of supersaturation on the crystal habit. With the introduction of the BCF theory and the 2‐D growth mechanism in the above mentioned approach predictions have been carried out for paracetamol and caprolactam crystals, respectively. The verifications by crystals grown from solutions as simulated by the computer model give good agreements. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth of borax crystals by spiral mechanism

Borax crystals grown at low supersaturation values are described. A brief report about microtopographical studies of these crystals is presented. Growth spirals observed on almost all the habit faces except those in contact with the bottom of the nucleation cell are described and discussed. It is established that all these crystals have platelet form in the initial stages of crystallization and as growth proceeds they develop and grow by spiral mechanism. The conditions under which the screw dislocations play the role in the development and growth of the crystals have been worked out.     

Über die Züchtung von ZnS-, ZnSe- und ZnTe-Einkristallen unter Anwendung der chemischen Transportreaktion

In connection with investigations on the synthesis of ZnS, ZnSe and ZnTe single crystals by chemical transport using iodine as transport agent in sealed tubes the mechanism of mass-transport and the relationship between material-transport and growth process were studied. In this way the optimum conditions for growing single crystals were found. The dependence of the transport rate on the undercooling ΔT, on the diameter of the ampoule and on the pressure in the system is described. Relative large crystals in good quality could be propared by influencing the nucleation and the growth process by help of well defined transport rates. In all cases crystals with sphalerite structure only were obtained. The habit with the most common faces (110), (111) and (211) was found to be predominant. The dominant habit is responsive to variations in the experimental parameters. The crystal perfection have been determined by etch patterns and by X-ray topography.     

A Pragmatic Model for the Simulation of Self-induced Striations in Quartz Crystals

A mechanism is investigated which might lead to fluctuations in the growth of quartz crystals due to the periodic incorporation of impurities. The model ought to be applicable also to the incorporation of stoichiometric partners during the growth of complicated crystals from non-stoichiometric melts. The processes have been simulated with help of an equivalent circuit experimentally and by computation. Some typical cases are presented in the paper.     

Growth of Potassium Sulphate Crystals by Silica Gel Technique

Single and transparent crystals of potassium sulphate up to 30 × 3 × 3 mm in size have been grown by silica gel technique, using various methods (two-layers three-layers and hybrid gel technique) which are described. The effects of the three differents alcohols (used as top solutions) upon the quality and nucleation of crystals are also reported. The “growth and equilibrium” morphologies and microstructures of the habit faces are discussed.     

掺杂TGS晶体的生长及热释电性能研究

选择重稀土离子Dy3 为掺杂阳离子,DL-丙氨酸与L-谷氨酸部分取代甘氨酸分子,生长了不同掺杂配比的TGS晶体。生长和测试实验表明,掺杂TGS晶体较纯TGS晶体易于生长。将掺杂晶体生长溶液的pH值控制在1~4,可改变掺杂晶体的结晶习性。用ICP发射光谱测试了掺杂晶体中稀土元素的含量,用X射线粉末衍射法测定了晶格参数,结果表明:元素已进入晶体,晶格参数稍有变化,但掺杂晶体的对称性仍为C2-2。通过测量掺杂晶体的电滞回线,得到了内偏压场,还测量了各样品的热释电系数、自发极化强度,作了温度曲线,并分析了各掺杂剂对提高热释电性能和锁定极化的作用。结果表明:是有应用前景的热释电材料。     

The effect of solvents and crystallization conditions on crystal habit of cholesterol

The effect of various organic solvents as well as the crystallization conditions on the crystal habit of anhydrous cholesterol have been studied. Both plates and needle-like crystals can be obtained in a particular solvent depending on the degree of supersaturation of the solution. However, the crystals grown at about the same supersaturation, from different solvents, show differences in their habit indicating dependence on the solvent-solute interaction. Thus, it is advisable not to identify needle-like crystals with anhydrous-cholesterol and plates with mono-hydrate cholesterol without specifying the crystallization conditions. A prediction on the crystal habit length to width ratios can be made using those parameters.     

无序激光晶体及其超快激光研究进展

激光是受激辐射的光放大,所辐射的波长取决于增益介质中关键电子的能级结构,特别是其最外层电子的状态决定了可能实现的激光特性.激光发展60年来,激光晶体作为激光的重要激活材料,推动了激光技术的进步和普及,是一个研究历史长而又异常活跃的研究领域.当前,超短超强脉冲激光在加工、医疗、国防等关系国计民生的领域有重要需求,适合超短...     

Influence of emulsion types on nucleation kinetics and growth habit in the cooling crystallization

Experiments on unseeded batch cooling crystallization were made to investigate the influence of emulsion [solution in non‐solvent (S/NS) emulsion and non‐solvent in solution (NS/S) emulsion] on crystal size and growth habit of various materials such as hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine, ammonium sulfate, potassium dihydrogen phosphate (KDP), and γ‐glycine. Size of crystals obtained from the S/NS emulsions was found to be significantly larger than that obtained from the NS/S emulsions. Those results were explained by broad induction time distribution of nucleation in the isolated solution droplets and subsequent seeding effect by free movement of early‐induced crystals by vigorous agitation. As a result, the population density of crystals was shown to be smaller in the S/NS emulsions than that in the NS/S emulsions. In the S/NS emulsions, desupersaturation rate should be slow and high supersaturation is subsequently generated during crystal growth stage. Therefore, it may be concluded that crystal morphology of the materials with supersaturation dependent growth habit, such as ammonium sulfate, KDP and γ‐glycine, can be controlled by selection of emulsion type.     

Growth habit of crystals of refractory compounds prepared from high temperature solutions

The growth habit of single crystal refractory compounds (borides, carbides and silicides) obtained using a solution-melt method involving various growth conditions is reviewed. The effect of external and internal factors on the growth habit is analyzed. The influence of such external factors as the cooling mode, the cooling rate, the effect of variation of solute concentration, the stoichiometry of the initial components, the presence of additives in the system, the change of the maximum soaking temperature, the nature of the initial components and the solvent metal and microgravity on the growth habit are described. Examples of various anisotrophic properties in crystals of refractory compounds as well as data on crystal michrohardness anisotropy, obtained by the authors, are given. In conclusion the comparative evaluation of the effect of external factors on growth habit is provided.     

单掺Rb+和Cs+的KTP晶体生长及其电导率

采用高温溶液降温法在掺质浓度均为5mol;的KTP-K4溶液中分别生长了单掺Rb+和Cs+的KTP晶体,发现掺质改变了晶体生长习性,在相应生长体系中掺质Rb+和Cs+的分配系数分别为O.646和0.08,掺质KTP晶体的晶胞参数a0和b0比纯KTP晶体者略有增长.通过掺Rb+或Cs+,KTP晶体的c向电导率明显降低,但晶体在350～1100nm范围内的光透过性质未受影响.     

Growth of Gallium Orthophosphate Single Crystals under Hydrothermal Conditions

Gallium orthophosphate (GaPO₄) single crystals have been grown from phosphoric acid solutions under hydrothermal conditions. The crystals have been studied in terms of twinning because of the strong effect of this structural defect on the piezoelectric properties. The growth rates of individual faces have been compared to each other by considering the dipyramidal habit of the grown crystals.     

On the Formation of Thick Sector Boundaries by Appearance and Disappearance of Faces of Crystals

Wide sector boundaries revealed in KBC crystals by chemical etching have been observed and analysed. It was established that the boundaries represent sectors of small faces appearing and vanishing in the habit during crystal growth. This nature of thick boundaries has been confirmed by the analysis of values of relative growth velocities of faces with respect to the critical velocities governing the presence of faces on growing crystals.     

添加剂对硝酸钾结晶习性影响的研究

研究了Fe3+、Bi3+、pb2+、EDTA、柠檬酸、季铵盐和十二烷基磺酸钠共7种添加剂对硝酸钾结晶习性的影响,对不同添加剂在晶体表面的吸附机制进行了初步探讨.结果表明,随金属离子Bi3+、pb2+和EDTA浓度的增高,硝酸钾晶体c轴方向生长速度增大,晶体呈棒状;当柠檬酸添加量为100mg/L时,硝酸钾变为长片状;其他添加剂对硝酸钾结晶习性的影响效果则不明显.尽管某些添加剂可以改变硝酸钾的结晶习性,但粉末衍射和单晶衍射分析进一步证明,添加剂并未改变其晶胞参数及结构.     

软X射线分光晶体琥珀酸氢十四酯的合成及结晶习性研究

本文合成了软X射线分光晶体琥珀酸氢十四酯(THS).通过红外光谱、差示量热扫描等手段对所合成样品进行表征和鉴定.对THS在苯、甲苯、二甲苯、异丙醇等溶剂中的自发成核和结晶形态进行了研究,结果表明THS在苯、甲苯和二甲苯中表现出良好的结晶习性.采用平衡法测定了THS在苯、甲苯和二甲苯中的溶解度曲线.综合考虑结晶习性和溶解度情况,可选择甲苯作为晶体生长的溶剂进行单晶生长实验.