KCl Single Crystals Research Articles

Dielectric measurements on Li + doped KCl

We report on an investigation of the temperature dependence of the complex dielectric constant of KCl single crystals containing Li + tunneling defects. Our results partially agree with the theoretical prediction for resonant interaction between a low frequency external field and tunneling systems with an energy splitting of 1.1 K. Additionally to resonant contributions, we find significant contributions from relaxation processes. They depend on the defect concentration and on frequency. The results suggest the presence of a broad density of states at energy splittings below 100 mK.

Influence of a state of impurities on the interaction between a dislocation and impurities in KCl single crystals

The strain-rate cycling test during the Blaha effect measurement at 80 to 240 K has been carried out for two kinds of single crystals: quenched and annealed specimens of KCl:Sr2+. It was found that the force-distance profile, which expresses the interaction between a dislocation and impurities, cannot be approximated by the Fleischer's model when I–V dipoles turn into aggregates for KCl:Sr2+, and that the activation energy for the break away of a dislocation from impurities becomes small for the annealed specimen, compared with the quenched one. Furthermore, the critical temperature,Tc, for the annealed KCl:Sr2+ is slightly smaller in comparison with that for the quenched one.

Optical absorption of theFcenter as function of the temperature

Abstract The temperature shift of the F absorption band for KBr and KCl single crystals was experimentally and theoretically determined. The theoretical calculations are based on the pseudopotential method using different wave functions and assumed a linear thermal expansion coefficient for the crystalline lattice. The change of F-center absorption energy due to collisions with the thermally vibrating lattice is calculated. This contribution is small. The measurements agree fairly well with the results obtained using the present model.

Creep Behavior of Potassium Chloride–Rubidium Chloride Solid Solution Alloys

The creep behavior of three KCl–RbCl solid solution alloys and pure KCl and pure RbCl single crystals compressed along the 〈100〉 direction was investigated at 600°C at stresses between 0.5 and 15 MPa. The reduced primary creep stage, a value of the stress exponent of about 3 for the KCl–20 mol% RbCl and KCl–30 mol% RbCl alloys versus about 5 for pure KCl and pure RbCl and the results of the stress reduction tests for these alloys are in good agreement with creep behavior observed in class I metallic solid solution alloys, where the creep rate is controlled by a dislocation glide process. The dislocation substructure developed in the KCl–RbCl alloys consisted of well‐developed subgrains.

Temperature dependence of O ? 3 electron paramagnetic resonance signals in KCl

An ozonide molecular ion O–3 has been detected by EPR spectroscopy in KCl single crystals doped with 2% KNO3 in the melt and X-irradiated at room temperature. The temperature dependence of the O–3 EPR signals was investigated from 10–60 K and a gradual transition from monoclinic to orthorhombic g-tensor symmetry was found. An unexpectedly strong variation of two principal g values, one corresponding to the direction perpendicular to the molecular plane, the other with the axis connecting the two outer oxygens, was observed. These results are discussed in relation to the possible allocation of the O–3 to a mono- or a tri-vacancy site. The latter model has been well established by other authors for S–3 and Se–3 defects in several alkali-imetal halides. Other defects with an electronic structure comparable with that of O–3, for instance SO–2 and SeO–2, are believed to replace only one halide ion.

Interaction between a Dislocation and Monovalent Impurities in KCl Single Crystals

The temperature dependence of strain rate sensitivity is investigated superimposing an ultrasonic oscillatory stress during the plastic deformation of KCl single crystals doped with monovalent impurities, Br− and I−. The effective stress due to monovalent weak obstacles which lie on the mobile dislocation with largest separation, is obtained from the plots of the strain rate sensitivity and the stress decrement due to application of the oscillation. It is found from the temperature dependence of the effective stress that the force–distance profile of the interaction between a dislocation and monovalent impurities is a triangle. Die Temperaturabhängigkeit der Verformungsgeschwindigkeit wird für den Fall untersucht, daß eine oszillierende Ultraschallspannung während der plastischen Deformation von KCl-Einkristallen, dotiert mit einwertigen Verunreinigungen, Br− und I−, überlagert wird. Die effektive Spannung wird aufgrund der einwertigen, schwachen Hindernisse, die auf den beweglichen Versetzungen mit größtem Abstand liegen, aus der Sensibilität der Verformungsgeschwindigkeit als Funktion des Spannungsdekrements infolge der Oszillation erhalten. Es wird aus der Temperaturabhängigkeit der effektiven Spannung gefunden, daß das Spannungs–Abstandsprofil der Wechselwirkung zwischen einer Versetzung und einwertigen Verunreinigungen dreieckig ist.

Electron paramagnetic resonance of phosphate-derived radicals in KCl

The authors examined the EPR spectrum of KCl single crystals doped with either K3PO4 or P2O5 after X-ray or neutron irradiation. Two new related O- defects and two phosphorus-containing radicals were detected. One of the latter is identified as a PO22- radical in an anion vacancy.

Oxidation of supported and unsupported polymeric μ-fluoro(phthalocyanine) aluminium(III)

The polymeric, fluoro-bridged phthalocyanine complex [Al(Pc)F] n [J.P. Linksy, T.R. Paul, R.A. Nohr and M.E. Kenney, Inorg. Chem., 19 (1980) 3131] has attracted considerable attention since it can be doped using a variety of oxidizing agents to give conducting materials [R.S. Nohr, P.M. Kuznesof, K.J. Wynne, M.E. Kenney and P.G. Sieberman, J. Am. Chem. Soc., 103 (1981) 4371; P. Brant, D.C. Weber, S.G. Haupt, R.S. Nohr and K.J. Wynne, J. Chem. Soc. Dalton Trans. (1985) 269; D. Djurado, A. Hamai and C. Fabre, Synth. Met., 29 (1989) 71F and refs therein]. However, many features of the doping process, particularly structural aspects, remain unclear. Evaporation of [Al(Pc)F] n onto single crystal KCl results in an epitaxial film which has been structurally characterized by high resolution transmission electron microscopy [J.R. Fryer and M.E. Kenney, Macromolecules, 21 (1988) 259]. In the present work oxidation of [Al(PC)F] n supported on KCl or silica wafers had been compared with oxidations performed on polycrystalline material in the presence of MeCN. Oxidizing agents used include hexafluorides (UF 6, MoF 6, WF 6), pentafluorides (AsF 5, PF 5, IF 5) halogens (Cl 2, Br 2, I 2) and the NO + cation. The colour change, blue→purple occurs in all cases. There are spectroscopic similarities between film and polycrystalline reactions and the oxidized products are freely soluble in MeCN. The spectroscopic and TEM data suggest that in many cases oxidation is accompanied by depolymerization. Depolymerization appears to be important also when [Al(Pc)F] n is protonated by CF 3CO 2H and CF 3SO 3H.

Antireflection coatings on KCl single-crystal optical elements for optical systems of continuous and pulsed technological lasers

Several single- and double-layer 3ntireflection coatings on KCl single crystal plates were deposited in vacuum by thermal evaporation. The optical properties of the coatings (reflectance, transmittance and absorption) were theoretically investigated using iterative and matrix methods. Experimental studies of the optical, mechanical and moisture-resistant properties of the antireflection coatings in combination with the theoretical results show that the best coating system is PbF 2/ZnSe/KCl. The surface reflectance of this coating is about 0.05% and the absorption of KCl plate with such a coating is 0.05%, which is an acceptable value for CO 2 laser systems with powers 10 kW and over.

Thermoluminescence in KCl crystals containing yttrium

Thermoluminescence (TL) of X-irradiated KCl single crystals containing different concentrations of yttrium is studied in the temperature range 30–250 °C, in which the TL intensity is found to decrease with increasing yttrium concentration. In all the yttrium-doped KCl crystals, the TL glow curves show three glow peaks: T 1 peak (85–100 °C), T 2 peak (115–120 °C) and T 3 peak (160–180 °C). Annealing of the irradiated crystals doped with 1 mol.% yttrium shows the elimination of the T 1 peak whereas the F-bleaching of the irradiated crystal at room temperature increases the intensity of the T 2 peak while decreasing the intensities of the other glow peaks. From these observations, the T 1 peak is attributed to background impurities, the T 2 peak to yttrium-related centres and the T 3 peak to F-centres. The trap depths corresponding to these glow peaks are calculated using various peak methods.

ＫＣｌ単結晶の球状圧子による変形機構 Ｉ．鋼球圧子押し込みの場合

The indentation test is probably the simplest method of estimating the strength of material under the frictional condition that the asperity tips are pressed into other body and that wear debris are scratched between two bodies. With the advancement of techniques of revealing dislocations in crystals, it has been thought possible to obtain a right understanding of the deformation in the material with a single crystalline structure caused by indentation.In the present study, KCl single crystal was indented with a steel ball to examine the dislocation structures associated with indentation at various loads. The slip systems and the range of deformed area were investigated in detail on the indented surface and on its cross section by using a dislocation etching technique.The results obtained are as follows:(1) The deformed area on the indented surface consists of a circular high dislocation density area and the area of comparatively low dislocation density shaped like wings and extended in the ‹110› and ‹100› directions.(2) Dislocation patterns on the indented surface and on its cross section consist of etch pit rows that belong to the {110}90 and {110}45 planes, respectively.(3) The plastic deformation range is affected by the diameter of indentor under comparatively high loads, but not under exceedingly low loads.

ＫＣｌ単結晶の鋼球および四角すい圧子押し込みによる変形

In order to elucidate the mechnism of friction and wear, it is necessary to have a knowledge on deformation in materials produced by invasion of sharp projections or wear particles.In this study, the cleaved faces of KCl single crystal were indented with a steel ball or a Vickers diamond indentor. The deformation and hardness around the indentation were examined from macroscopic viewpoints, and the dislocation patterns were observed from microscopic one. The results obtained are as follows:(1) The indents formed on the indented surfaces with a ball or a pyramid were not perfectly circular nor square in shape due to the crystal anisotropy.(2) The appearances of the pile-up and sink-in around indents were clarified.(3) The strain hardening around the indent was more active in the ‹110› direction than in the ‹100›.(4) The deformed area on {100} face with a ball or pyramidal indentor consisted of a high dislocation density range and a wing shaped area of comparatively low density extended along the ‹110› and ‹100› directions.(5) The hardness and the dislocation density were related each other.(6) The etch pit patterns in the cleaved cross section were observed on {110}45 faces.

ＫＣｌ単結晶の球状圧子による変形機構 ＩＩ．鋼球圧子摩擦の場合

ＫＣｌ単結晶の球状圧子による変形機構 ＩＩ．鋼球圧子摩擦の場合

New method for in-situ observation of moving dislocations in KCl crystal using laser-light scattering

Abstract The dislocations moving on slip planes in a KCl single crystal under an applied load were observed successfully by a 90° angle light scattering method using a high-power Ar-ion laser (2W for a wavelength of 514 nm). The photographs of stationary dislocations were taken by an scanning type optical microscope. The image of such dislocations was very sharp and uniform compared with that of grown-in dislocations. The dynamic behavior of moving dislocations was observed by an image intensifier to intensify the scattered light from dislocations. The motion of dislocations was jerkey under a constant load in almost all cases.

Deformation Luminescence in gamma-irradiated KCl single crystals

Abstract Deformation Luminescence(DL) is studied on KCl crystal colored by γ-irradiation. The spectra analysis of DL and thermoluminescence reveals that F-center plays a role as electron donor through the interaction with moving dislocation and V2-center is a probable luminescence center. A theory is presented for understanding the deformation rate and temperature dependences of DL intensity.

Oxidizing properties of transition metal hexafluorides towards p-block elements and polymeric μ-fluoro(phthalocyanine)aluminium(III)

The behaviour of UF 6, MoF 6 and WF 6 towards the p-block elements Se, As, Sb and Bi has been studied using MeCN as solvent. The results obtained, together with previous work involving I 2, Br 2 and Te with MoF 6 and UF 6 [1], have enabled a detailed picture of p-block element redox chemistry in MeCN to be obtained. Complex cation, hexafluorometallates (V) have been isolated for all the elements examined and structures for the cations are proposed on the basis of spectroscopic studies. Oxidation of [Al(Pc)(μ-F)] n Pc = phthalocyanine dianion, by the hexafluorides which has been reported previously using microcrystalline material [2], occurs also in the presence of MeCN. Soluble products are obtained whose electronic spectra are very similar to those of [Al(Pc)(μ-F)] n dissolved in the protonic acids CF 3CO 2H, CF 3SO 3H and HSO 3F. Thin films of [Al(Pc)(μ-F)] n, grown by evaporation onto single crystal KCl or silica wafers, are also oxidised when exposed to UF 6, MoF 6 or WF 6 vapours. The oxidised films are stable in the absence of moisture unlike those obtained using I 2 as oxidant, where the redox reaction appears to be reversible. We thank the SERC for support of this work.

Chemical analysis of photoassisted intercalation reaction of SnS 2 single crystal under cathodic polarization

Cathodic reactions at (001) SnS 2 single crystal—KCl aqueous solution were investigated analytically both in the dark and under illumination. Reductive decomposition of the SnS 2 host occurred in the dark besides intercalation of the hydrated K + ion. However, the former was inhibited by illumination.

Studies on F-band absorption of irradiated KCl single crystals excited with laser light

The absorption in the F-band of KCl single crystals after X-ray irradiation and subsequent excitation with laser light is studied. Similar investigations have been carried out when these crystals are subjected to high a.c. electric fields prior to X-ray irradiation and also at elevated temperatures. The effect of laser excitation on γ-ray irradiated samples is studied. An attempt is made to interpret the results in terms of the disorder that sets-in in these crystals.

Magnetic behaviour of Fe(CN)3- 6 in surroundings of low symmetry studied by EPR

The Fe(CN)3- 6 complex doped in NaCl and KCl single crystals was examined by EPR at liquid-helium temperatures. Various Fe(CN)3- 6 centres with local symmetries D2h, C2, and Cs have been identified. The corresponding EPR spectra are characterized by an effective electron spin-½ with a high degree of g anisotropy. A detailed ligand-field analysis has enabled a full establishment of the models for the observed centres. Quantitative information about the influence of the associated cation vacancies on the energy of the d orbitals has also been obtained. Finally, the g anisotropy in relation to the splitting and the ordering of the energy levels is discussed.

Structure of Octacyanophthalocyanine Derivatives Prepared by CVD

Phthalocyanine compounds have been attracting a good deal of attention as semiconductors and photoconductors. We have studied the crystal structure of octacyanophthalocyanine(2a)-metal complex crystal prepared by CVD reaction of 1,2,4,5-tetracyanobenzene (TCNB:1a) with metal films by HREM. In the case of 2a-K complex crystal, the high resolution image of the crystal showed a grid pattern with a spacing of 1.57nm, as is shown in Fig.1. The planar molecules of 2a stacked along a column to coordinate with the intercalated potassium atoms in the complex crystal. In this study, we examined the structure of the films prepared by CVD reaction of TCNB derivatives, which were introduced iodides(1b) or chlorines(1c) into 3 and 6 positions of TCNB, with KCl.The films were prepared on a cleavage face of KCl single crystal by heating with the powders of 1b and 1c in an evacuated sealed tube at 350 C for 12h. The specimens were examined in a JEOL-200CX microscope equipped with a minimum dose system.