氧化锌单晶的水热生长与结晶习性

本文应用水热生长法,采用双温区高压反应釜,黄金内衬(φ35mm ×2mm),碱性溶液矿化剂,生长出了毫米级的透明氧化锌单晶,最大单晶可达2mm ×3mm ×6mm.所生长氧化锌晶体为纤锌矿型的六方晶体,晶体呈上部锥形的六棱柱体,{10(1-)1}、{10(1-)0}和{000(1-)}面有较大的显露平面.本文中从温差和填充度方面研究了实验条件对ZnO晶体的生长及其形貌的影响,使用黄金内衬前后的结果表明,用贵金属内衬可以有效阻止釜内壁杂质的进入,使晶体完整透明.     

Mn、Cu共掺ZnO磁性的研究

本文采用水热法,分别以ZnO、Zn(OH)2为前驱物,添加一定量的MnCl4.4H2O和CuSO4.2H2O, 3mol/LKOH作矿化剂,温度430℃,填充度35%,反应24h,制备了Mn、Cu共掺ZnO晶体。当前驱物为Zn(OH)2时,所得晶体大部分为短柱状晶体,显露正负极面{0001}、{0001-}、负锥面-p{101-1-}和柱面m{1-010},长度约为30 ～50μm。少部分晶体为单锥六棱柱状,显露正锥面p{101-1},柱面m{1-010},负极面-c{0001-},晶体的长度约为100μm,长径比为5:1。当ZnO用作前驱物时,短柱状晶体长度大约为10 ～30μm,晶体的六棱对称性都出现较大的偏差。X射线荧光能谱分析表明,前驱物为ZnO、Zn(OH)2时,Mn离子含量在分别为3.19%和1.62%原子分数,没有检测到Cu离子。虽然Mn、Cu离子的掺入会明显影响晶体形态,磁性测量显示掺杂Mn、Cu的ZnO仍为反铁磁。     

High-Temperature Crystallization,Composition, Structure,and Certain Properties of Rare-Earth Gallium Borates

Solution-melts based on PbF₂—B₂O₃ and Bi₂O₃—B₂O₃ were used in studying the stability regions and for growth, by way of spontaneous crystallization, of crystals up to 3 mm in size of twelve compounds having the general formula RGa₃(BO₃)₄. All of these compounds are isostructural with carbonate mineral huntite. Their composition is highly dependent on that of the crystallization medium. The facing of the crystals is characterized by a small number of simple forms {101 1}, {112 0}, {21 1 0}, and less frequently {022 1}, {0112}, {404 1}. The examined parameters include the IR spectra, luminescence spectra, heat of formation from oxides, harness (6 to 8 units on the Mohs scale) and others.     

Chiral Etch Pits on Sodium Chlorate Crystals

Microtopography of {100}, {110}, {111}, and {210} surfaces of sodium chlorate crystals etched in various solvents has been studied by optical microscopy. It has been established that etch pits formed on left- and right-handed crystals are chiral, and directions of dissolution steps reveal bond chains of the structure.     

Dislocation etching in V3Si

Dislocations in as-grown and in plastically deformed V₃Si single crystals have been studied by chemical etching. In as-grown crystals dislocations are partly arranged in small-angle boundaries parallel to {001}, {011}, and {112} planes. The total dislocation density amounted to (10⁵−10⁶) cm⁻². After plastic deformation at elevated temperatures indications for slip and climb processes were observed. The dislocation density increased to 10⁷ cm⁻².     

Kinetic Investigations within the Transition Region from Polyhedral to Skeletal Growth Mode (V). Growth Kinetics of the Pyramidal Face of Zinc Single Crystals under Diffusion Conditions

The growth kinetics of the pyramidal face of zinc single crystals is studied in the presence of argon. The curves size vs. time provide evidence that smaller crystals grow in a kinetic regime and after reaching a certain critical size their growth continues in a diffusion regime. The growth kinetics of faces {101 } and {0001} are compared. It is established that the growth of both faces simultaneously changes from a kinetic to a diffusion growth mode. During the transition between the two regimes, however, loss of the morphological stability only of the smooth {0001} face is observed, while the {101 } face with macro steps formed on the surface acquires a skeletal shape after prolonged growth. It is shown that the appearance of morphological instability depends on the surface structure of the crystal faces.     

优质立方六面体金刚石大单晶的生长研究

高温高压静压触媒法合成的金刚石单晶,往往呈现六八面体形貌,因为立方六面体单晶{100}面的生长区间相对较小.本研究利用高温高压温度梯度法,自制Fe-Ni合金触媒,通过对合成组装和工艺进行合理调整后,控制晶体在相对低温适合{100}面生长区域内生长,得到的晶体均呈现完整立方六面体形貌;同时为抑制包裹体和其他杂质的进入,人为的提高晶体的径向平铺生长速度,抑制其轴向生长速度.以在33 h内合成的优质立方六面体晶体为例,晶体最大方向尺寸达到7.3 mm,重1.2克拉,其径向生长速度达到0.22 mm/h,轴向生长速度仅为0.08 mm/h,增重速度为7.3 mg/h.     

Modeling of the shape of polyethylene oxide single crystals and determination of the kinetic crystallization parameters: Theoretical and experimental approaches

The curvature of faces of polymer single crystals is described by the system of Mansfield equations, which is based on the Frank-Seto growth model. This model assumes the velocity of nucleus steps to be the same for their propagation to the right and left and is valid only for symmetric crystallographic planes. To describe the shape of polyethylene oxide single crystals grown from melt and limited by the {100} and {120} folding planes, it is assumed that the layer velocities to the right and left are different on {120} faces. This approach allows modeling, with a high accuracy, of the observed shapes of polymer single crystals grown at different temperatures, which makes it possible to determine unambiguously the fundamental crystallization parameters: the dimensionless ratio of the secondary homogeneous nucleation rate to the average velocities of nuclei along the crystallization planes and the ratio of nucleus velocities to the right and left. In addition, it was found that a known macroscopic single-crystal growth rate can be used to determine the absolute values of the secondary homogeneous nucleation rate and the velocities of nuclei along the growth plane.     

Geometric modeling of homoepitaxial CVD diamond growth: I. The {1 0 0}{1 1 1}{1 1 0}{1 1 3} system

Plasma-assisted CVD homoepitaxial diamond growth is a process that must satisfy many stringent requirements to meet industrial applications, particularly in high-power electronics. Purity control and crystalline quality of the obtained samples are of paramount importance and their optimization is a subject of active research. In the process of such studies, we have obtained high purity CVD diamond monocrystals with unusual morphologies, namely with apparent {1 1 3} stable faces. This phenomenon has led us to examine the process of CVD diamond growth and build up a 3D geometrical model, presented here, describing the film growth as a function of time. The model has been able to successfully describe the morphology of our obtained crystals and can be used as a predictive tool to predetermine the shape and size of a diamond crystal grown in a given process configuration. This renders accessible control of desirable properties such as largest usable diamond surface area and/or film thickness, before the cutting and polishing manufacture steps take place. The two latter steps are more sensitive to the geometry of the growth sectors, which will be addressed in a companion paper.Our model, applicable to the growth of any cubic lattice material, establishes a complete mapping of the final morphology state of growing diamond, as a function of the growth rates of the crystalline planes considered, namely {1 0 0}, {1 1 1}, {1 1 0}, and {1 1 3} planes, all of which have been observed experimentally in diamond films. The model makes no claim as to the stability of the obtained faces, such as the occurrence of non-epitaxial crystallites or twinning. It is also possible to deduce transient behavior of the crystal morphology as growth time is increased. The model conclusions are presented in the form of a series of diagrams, which trace the existence (and dominance) boundaries of each face type, in presence of the others, and where each boundary crossing represent a topology change in terms of number of faces, edges and vertices. We validate the model by matching it against crystals published in the literature and illustrate its predictive value by suggesting ways to increase usable surface area of the diamond film.     

Effect of flux composition on the morphology of KTiOPO<Subscript>4</Subscript> crystals

KTiOPO₄ crystals have been grown from flux of K₆P₄O₁₃ in the presence of K₂SO₄, Li₂SO₄, and Na₂SO₄ salts and V, Cr, Ni, Co, Cu, Mo, Ba, Ce, Er, and W impurities. The crystals grown are characterized by well-developed simple {100}, {011}, and {201} faces. In some cases, new ({111} and (031)) faces arise. Some distortion of crystals caused by their pulling in the [101] direction is observed.     

Morphology and orientation relations of BaCl2 precipitates in NaCl single crystals

In the present paper morphology and orientation relations of BaCl₂ precipitates in NaCl single crystals are described. It is shown that BaCl₂ precipitates of large dimensions are formed at the dislocations of a/2〈110〉{100}, the dislocation lines of which are oriented in the directions 〈210〉.     

水热法合成Zn1-xMnxO稀磁半导体

本文采用水热法在430℃,以3mol%.L-1KOH作矿化剂,填充度为35%,反应时间24h,合成了Zn1-xMnxO稀磁半导体晶体。所合成晶体具有ZnO纤锌矿结构,晶面显露正极面{0001}、负极面{0001}、菱面{1011}及负菱面{1011}晶体高度为5~30μm,径高比约为2:1。X荧光能谱(EDS)显示Mn原子百分浓度为2.6%(x=0.026)。晶体呈现低温铁磁性,居里温度50K。     

水热法合成Mnx Zn1-xO微晶体

本文采用水热法合成了MnxZn1-xO晶体,水热反应条件为3mol·L-1KOH作为矿化剂,填充度为35;,温度为430℃,在Zn(OH)2中添加一定量的MnO2为前驱物,反应时间为24h.通过X射线能谱仪测量了晶体中的Mn含量,随着前驱物中MnO2含量的增加,晶体中Mn的原子百分比随着增加,Mn最大原子百分比含量超过了2;,晶体的形貌具有纯ZnO晶体的六角柱形特征.显露柱面m{1010}、锥面p{1011}、负极面O面{0001}和正极面{0001}.晶体直径为50～200μm,高度为20～100μm.     

Growth‐Sector Boundaries and Growth‐Rate Dispersion in Potassium Alum Crystals

Crystals of potassium alum, pure and slightly doped with Cr³⁺, were grown from aqueous solution by slow temperature lowering. In addition, short re‐dissolution periods were introduced in order to provoke growth defects and changes of growth rates. Crystal slices of about 1 mm thickness were studied by conventional LANG X‐ray diffraction topography using MoKα radiation. For Cr‐doped crystals, boundaries between {100}, {100} and {111} growth sectors appear by pronounced dynamical X‐ray topographic contrast similar to that of stacking faults. Re‐dissolution experiments provoke the formation of inclusions on {100} faces, followed by an increase of the {100} growth rate by the factor of about six, relative to the neighboured {111} faces. X‐ray topographs show that this increase is correlated with the formation of dislocations, which interestingly have pure‐edge character. During further growth these dislocations penetrate the {100}‐{111} growth sector boundary and vanish from the {100} face, which slows down and finally adopts its former growth rate before re‐dissolution.     

Structural Conditionality of the Ionic Conductivity of MTiORO<Subscript>4</Subscript> (M = K,Rb; R = P,As) Single Crystals

The ionic conductivity σ_||c along the crystallographic axis c and the structural imperfection of the lattices of KTiOPO₄, RbTiOPO₄, and RbTiOAsO₄ single crystals with low defect concentration, grown by the high temperature solution growth technique, have been investigated by impedance spectroscopy and X-ray diffraction analysis. Isomorphic substitutions of Rb⁺ ions for conduction K⁺ cations in MTiOPO₄ crystals decreases the σ_||c value, whereas the substitution of As⁵⁺ ions for framework P⁵⁺ cations in RbTiORO₄ crystals increases the σ_||c value. The σ_||c values at 573 K are found to be 1.0 × 10^–5, 5.7 × 10^–6, 2.0 × 10^–6, and 3.3 × 10^–5 S/cm for the KTiOPO₄, RbTiOPO₄ {100}, RbTiOPO₄ {201}, and RbTiOAsO₄ crystals, respectively (the growth zone of the crystalline boule from which the samples were cut is indicated in braces).     

Growth and real structure of diamond films synthesized on polycrystalline tungsten substrates

X-ray diffraction studies of diamond films obtained by chemical transport reactions at the concentrations of 2% methane and 98% hydrogen under pressures of 10.7 and 21.3 kPa showed that they are textured. The character of the texture depends on the substrate temperature. The films have {110}, {311}, or double {110} + {311} textures. It is established that the dependence of the growth rate of diamond films on the substrate temperature has maxima. The diamond films are finely dispersed and are characterized by pronounced micro-deformations and high dislocation densities. The temperature dependence of the growth rate correlates with the parameters of the real structure of the films.     

Conditions of Formation of Calcite Crystals of Tabular and Acute Rhombohedral Habits

Calcite crystals are grown under pure conditions by the method of counterdiffusion of calcium and carbonate ions in water. An extension of the diffusion method is used making possible the crystallization of calcite in a medium containing calcium or carbonate ions in excess of their stoichiometric amounts in calcite. Calcite crystals grown in the presence of an excess of Ca²⁺ ions exhibit an elongated habit determined by the prevailing development of some of the acute negative rhombohedra φ. {022 1}, θ. {044 1} or π. {088 1}, whereas with an excess of CO ions the habit varies from thick -to fine-tabular due to the considerable development of the pinacoid (c {0001}). The habit of crystals grown in a medium in which both ions are approximately in stoichiometric amounts or in which the excess of one of them frequently alternates with an excess of the other, is determined by the supersaturation and varies from basic rhombohedron to acute rhombohedron m. {404 1}. The results are discussed in the light of some of the existing theoretical ideas on the influence of admixtures on habit. It is shown that the order of morphological importance which can be derived on the basis of various extensions of Bravais' law agrees neither with the experimental results nor with the observations in nature. The particular habits observed in experiments, tabular and acute rhombohedral, are exactly those which Kalb had included in his morphogenetic order of calcite crystals as first and fifth habit types. Since they are the result of specific conditions in the medium they ought to deviate from the general order. The remaining three habit types, therefore, will determine the habit variations of calcite due to the decrease of supersaturation.     

Berechnung der Verteilungsfunktion für einen periodisch veränderlichen Verteilungskoeffizienten beim Kristallwachstum nach dem Kyropoulos-Verfahren

Periodically appearing segregation processes during Kyropoulos growth of doped single crystals were treated quantitatively using a sinusoidally varying distribution coefficient. The shape of the average dopant concentration and of the amplitude of the oscillation of the dopant could be calculated as a function of the crystallized part of the melt. Characteristic parameters influencing this shape are discussed. The calculation is applied to the growth of Ca doped KCl crystals.     

Studies of the Growth Habits of the AgGaSe2 Single Crystal

High quality AgGaSe₂ single crystals with 20 mm in diameter and 55 mm in length have been grown by the modified Bridgman technique and the growth habits of AgGaSe₂ single crystals have been investigated in detail. It is found that the shape of the growth ampoule affects greatly the nucleation and the growth of AgGaSe₂ single crystal. A new cleavage face (101) and the natural faces are observed in the as-grown crystals. For some cases, the growing direction is normal to the (316) face.     

Semiopen Physical Vapour Transport Growth of Urotropine Crystals

It is reported for the first time the growth of urotropine (HMT) crystals by a semiopen physical vapour transport (SOPVT) technique. HMT crystals, approximately 1 cm³ in volume, are grown on a glass pedestal from solution-grown seeds. The final habit of the crystals is limited by rhomboedrical {110} faces which develop on an otherwise hemispherical shape. Preliminary X-ray diffraction investigations (rocking curves and topographs) point to a still non-homogeneous crystal structure, which very likely originates at the seed-crystal interface. However, in comparison with solution-grown samples, the best structural quality was observed in a SOPVT-grown sample.