On the Abnormal Conductivity of the Surface (001) of Alkali Halide Crystals

Crystallography Reports - Surfaces (001) of alkali halide crystals (KCl, NaCl), which were obtained by cleavage in air and ultrahigh vacuum, have been studied by Auger electron spectroscopy. It is...     

On the Interface Shape of Semitransparent Crystals obtained by the Bridgman Method

The effect of the pulling rate and of the furnace configuration on the interface shape in semitransparent crystals grown by the vertical Bridgman method are studied by finite—element analysis.     

LnX3型稀土卤化物闪烁晶体的闪烁性能

本文简要综述了LnX3型稀土卤化物闪烁晶体的发展历史与研究现状,对几种常见晶体(CeF3,LaF3,LuCl3,LaCl3,LuBr3,LaBr3)的物理、化学性质、晶体生长及闪烁性能等进行详细总结归纳,同时指出了当前具有优异闪烁性能的LaCl3:Ce和LaBr3:Ce晶体亟待解决的问题、未来的发展方向及其广阔的应用前景.     

Kinetic Nature of the Process of Microindentation into Alkali Halide Crystals

The investigation of the dependence of indentor intrusion depth on the time of load application and temperature for the alkali-halide crystals KCl, LiF, NaCl has been carried out. The dependence of indentor intrusion velocity logarithm lg ḣ in microhardness H appears to be linear in the investigated interval of loading times and temperatures. The data obtained may prove the thermofluctuational character of the microindentation process. — The activation energy of microindentation process almost coincides with the activation energies of the sublimation process.     

非氟卤化物闪烁晶体的研究现状和发展趋势

本文根据化学组成的特点将非氟卤化物闪烁晶体划分为AX、MX、RX₃、AMX₃、A₂MX₄、A₄MX₆、AM₂X₅、ARX₄、A₂RX₅、A₂A′RX₆、A₃RX₆、A₂TX₆型等,其中A、M、R和T分别代表+1价、+2价、+3价和+4价的金属元素,X代表除氟以外的卤族元素,A′表示与A不同的+1价金属元素。着重介绍了其中光输出高于40 000 ph/MeV的γ射线探测用闪烁晶体以及光输出高于20 000 ph/MeV的中子和γ射线双探测用闪烁晶体,并对它们的研究现状和发展趋势进行了简要评述。     

Growth Kinetics of Adenine Sulphate Crystals

The kinetics of growth and dissolution of adenine sulphate in 1.5 mol · 1⁻¹ H₂SO₄ at different super- and undersaturations has been studied. The solubility of adenine sulphate in H₂SO₄ was determined over the temperature range 20–50 °C. The growth rate of the (100) face is by about 25% higher than that of (111) and the crystal habit is changed by a high supersaturation almost to a bipyramide. The surface diffusion was determined as a prevailing processes and the BaS model gives the best fit with experimental data.     

甲酸根离子掺杂的卤化银中空穴陷阱效应分析

本文采用微波吸收介电谱检测技术,系统研究了甲酸根离子掺杂的立方体卤化银乳剂在35ps脉冲激光作用下所产生的光电子衰减行为,分析了甲酸根离子的空穴陷阱效应以及光电子衰减特性与掺杂条件的关系.通过分析不同位置和浓度甲酸根离子掺杂的立方体AgBr乳剂中光电子衰减时间特性,讨论了AgBr乳剂中甲酸根离子掺杂条件的变化对光电子衰减的影响,揭示了其空穴陷阱效应的作用机理.实验结果表明:不同浓度的甲酸根离子对立方体AgBr乳剂都有增感作用,最佳掺杂浓度为10-3mol/molAg;最佳掺杂位置是90;,说明了在接近微晶表面掺杂的空穴陷阱对提高乳剂感光度有较好的作用.     

Decanted Interface of Salol Crystals Grown from the Melt

The decanted surfaces of a crystal grown from the melt show various kinds of solidification markings formed either during growth or decantation. Some of the special features which are peculiar to decantation were discriminated from the real solid-liquid interface morphology by in situ observation of salol crystals under the microscope.     

Growth Kinetics and Mechanism of TGS Crystals

The growth kinetics of TGS crystals was studied at high supersaturations under the Curie temperature. The kinetics data proved that the crystal growth was mainly controlled by BCF surface diffusion model. The continuous growth was fitted to the growth rate data of (110) face. Its edge energy, Jackson factor, activity energies, kinetic coefficients were calculated.     

Electrical Processes Occurring at the Moment of Cleaving NaCl Crystals

The electrical processes occurring on cleaving tempered NaCl crystals have been studied by decoration methods on the scale of electron microscopy. The decorating agent, gold, was evaporated at the moment of performing the cleavage. The obtained decoration pictures differed from those described in the literature. Features similar to the propagation of waves were observed. They begin on cleavage steps and are mostly parallel to 〈100〉. On interaction of the “waves” with the steps or with other “waves” there arise black “threads” distinguished, the same as the wave boundaries, owing to a very high contrast on account of the higher density of decorating particles. The waves and threads are interpreted as microbreakdowns, which have also a two-stage character - stages of wave and thread formation, propagate along definite crystallographic directions, and occur at the boundary of strained sites. The charge sign of the waves is determined from the degree of coalescence of decorating gold particles. The detected waves reflect the occurrence of specific polarization states in local sites of the surface. These states are induced by local electric fields of a very high intensity occurring on cleaving the crystals. These polarization states disappear in 10-15 s after the cleavage is made due to neutralization of the charges. Analogy is drawn between polarization structures in form of waves and stable linear polarization bridges occurring in crystals between oppositely charged point defects and their assemblies.     

磷蛋白对牙本质晶脱矿动力学的影响

应用等组分晶体生长方法,研究了牙本质晶、羟基磷灰石、釉质晶脱矿动力学.并探索了磷蛋白对牙本质晶脱矿动力学过程的影响.实验条件为:溶液温度:T=37±0.5℃;溶液酸度:pH=4.5±0.03;初始离子强度:IS=0.15mol/L;溶液的饱和度:δ＝-0.60;-0.74;-0.86.研究结果表明:当δ=-0.60时,牙本质晶、釉质晶和羟磷灰石脱矿反应过程的特征明显不同.前两者的饱和溶解量比后者大一个数量级.羟磷灰石的特征反应周期比釉质晶和牙本质晶短15倍左右,初始反应速率慢30倍.牙本质晶脱矿初始反应速率Ri随δ的减低而快速增加.磷蛋白对牙本质晶的脱矿过程起抑制作用,但存在临界值.当磷蛋白在溶液中的浓度超过临界值后,其反应速率的变化很小.磷蛋白抑制作用在较大程度上依赖于溶液的饱和度.     

Formation of space-charge electric field and space charge during the cleaving of Alkali Halide Crystals

The “acoustic probe” method has been used for the measurement of the space-charge and polarization in the crystals LiF, NaF, KCl and NaCl exposed to mechanical action. It has been shown that large mechanical stresses in the bulk of crystals lead to the formation of space-charges and inhomogeneous polarization. The reason for this phenomenon is, probably, the motion of dislocation pile-ups.     

Growth Kinetics of Potassium-Dihydrogen Phosphate Crystals in Solution

Growth rate data of (101) faces of KDP crystals as a function of the relative supersaturation of the solution are analyzed on the basis of BURTON , CABRERA and FRANK surface-diffusion model applied to the growth from solution. The characteristic constants in the BCF function are determined for 50°C. Approximate values of the free activation energies for dehydration, desorption, surface diffusion and entering the kinks from the surface are calculated. The experimental data previously obtained by MULLIN and AMATAVIVADHANA and by BELOUET are also discussed.     

Effect of Carbamide Adsorption on the Growth Kinetics of the NH4Cl Crystals

This work supplements the adsorption model of 2D-isomorphism proposed earlier for the NH₄Cl-CO(NH₂)₂ system and reveals the correspondence between the growth rates of the NH₄Cl crystals in the presence of carbamide and the co-crystallization of carbamide with ammonium chloride. It follows from the kinetic data that the NH₄Cl · CO(NH₂)₂ impurity capture becomes significant when the carbamide concentration in solution is sufficient for almost monolayer adsorption of the impurity on the crystal surface and the onset of multilayer adsorption. The concentration of the guest phase intergrowths falls with the increase in the host crystal growth rate.     

CMTD晶体的分解过程原子力显微镜实时观测研究

用原子力显微镜实时观测了有机晶体CMTD(CdHg(SCN)4(H6C2OS)2)的表面分解过程,这一分解过程是以表面形貌变化来表征的,并且能反映分解过程中的一些固态反应的物理一化学变化机制.X射线能谱分析(EDAX)表明,相对于新鲜的CMTD晶体,在分解物中Hg低而S高;X射线衍射(XRD)表明分解物为非晶态;红外吸收光谱(IR)表明在CMTD晶体结构中的(H6C2OS)结构基元被分解为H2O和酸;量热分析(DSC)表明CMTD晶体在室温空气中确实有化学反应发生.本文用原子力显微镜实时记录了这一分解过程的形貌变化,发现这种非晶态的分解物的产生过程为:成核一核生长一核分散等.这是首次用原子力显微镜实时观测到这种分解过程.     

Surface Roughness and Kinetics of Spontaneous Transformation of Negative Crystals

Spontaneous isothermal transformation of negative crystals (vapcur inclusions) at temperatures close to the melting point is experimentally studied. Linear dependence of the transformation rate on supersaturation is established. This result shows that the evaporating crystal surfaces of the inclusions are moleculary-rough. Surface self-diffusion has no appreciable contribution to the transformation process of the molecularly-rough surfaces of diphenyl.     

Formation Entropy of Schottky Defects and Free Formation Enthalpy of Vacancy Pairs in Alkali Halide Crystals

The melting of alkali halides occurs probably at a critical mole fraction x_c = 3.2 · 10⁻⁴ of thermally created vacancies (Schottky defects). Using this value the formation entropy of Schottky defects is found to be s_S = (962.1 K mol/kJ L/T_m – 16.1) k (L, T_m heat and temperature of fusion, respectively). As to the free association enthalpy g_A = h_A – T_sA of (impurity-vacancy) complexes it is s_A = (10.8 h_A/eV – 2.56) k. Using this relation the concentration vacancy pairs is found to be smaller than that of isolated vacancies up to the melting point.     

Diffraction Investigation of Transient Processes of Domain Formation in Liquid Crystals

A coherent light diffraction method for investigation of domain formation in liquid crystal is proposed. The good agreement between theoretical predictions and the experimental results has been demonstrated.