KCl Single Crystals Research Articles

Size-dependent plasticity in KCl and LiF single crystals: influence of orientation, temperature, pre-straining and doping

Size effects in plasticity are mostly studied in metallic systems, but they are rarely investigated in ionic crystals. In this study, single-crystalline KCl and LiF pillars were fabricated by focused ion beam technique and compressed using a flat punch tip in a nanoindenter. The materials were investigated with regards to crystal orientation, test temperature, pre-straining and doping. The results show: (1) [1 1 1] LiF pillars do exhibit size effect with an exponent of −0.38, in contrary to no size effect in [1 1 1] LiF reported in literature; (2) [0 0 1] LiF, and [0 0 1] and [1 1 1] KCl have similar size-effect exponents of −0.68, −0.71 and −0.65, respectively; (3) the size effect of [1 1 1] LiF pillars is more sensitive to the temperature change than that of [0 0 1] LiF pillars; (4) pre-straining of [1 1 1] LiF pillars results in a reduced size effect; (5) the 0.05 mol% CaCl2 doping in [0 0 1] KCl slightly increases strength levels and does not change the size effect much. The magnitude of the size effects in ionic crystals can be attributed to the bulk stress level, but not the slip systems. In addition, a correlation between critical temperatures and size-effect slopes is illustrated, and the additivity of strengthening mechanisms is critically discussed.

Dispersion and Polar Component of Specific Surface Free Energy of NaCl(100), KCl(100), and KBr(100) Single Crystal Surfaces

Contact angle of ethylene glycol and formamide on (100) faces of NaCl, KCl, and KBr single crystal was measured, and the specific surface free energy (SSFE) was calculated. Dispersion component of the SSFE was 90.57, 93.78, and 99.52 mN·m-1 for NaCl, KCl, and KBr, respectively. Polar component of the SSFE was 1.05, 0.65, and 0.45 mN·m-1 for NaCl, KCl, and KBr. Such a large ratio of dispersion component of SSFE results from the neutrality of the crystal surface of alkali halide. Lattice component of alkali halide is 780, 717 and 689 kJ·mol-1 for NaCl, KCl, and KBr. The larger lattice enthalpy decreases dispersion component, and increases polar component of the SSFE. The larger lattice enthalpy is considered to enhance the rumpling of the crystal surface more strongly, and such rumpling is considered to decrease the neutrality of the crystal surface.

Elaboration and characterization of a KCl single crystal doped with nanocrystals of a Sb2O3 semiconductor

Undoped and doped KCl single crystals have been successfully elaborated via the Czochralski (Cz) method. The effects of dopant Sb2O3 nanocrystals on structural and optical properties were investigated by a number of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) analysis, UV-visible and photoluminescence (PL) spectrophotometers. An XRD pattern of KCl:Sb2O3 reveals that the Sb2O3 nanocrystals are in the well-crystalline orthorhombic phase. The broadening of diffraction peaks indicated the presence of a Sb2O3 semiconductor in the nanometer size regime. The shift of absorption and PL peaks is observed near 334 nm and 360 nm respectively due to the quantum confinement effect in Sb2O3 nanocrystals. Particle sizes calculated from XRD studies agree fairly well with those estimated from optical studies. An SEM image of the surface KCl:Sb2O3 single crystal shows large quasi-spherical of Sb2O3 crystallites scattered on the surface. The elemental analysis from EDAX demonstrates that the KCl:Sb2O3 single crystal is slightly rich in oxygen and a source of excessive quantities of oxygen is discussed.

Growth of KCl crystal by Czochralski method and influence of nanodiamond impurity on its hardness and optical properties

AbstractKCl alkali halide crystal with different nanodiamond impurity was grown by Czochralski method. X‐Ray diffraction of the outcome samples reveals that they are still single crystal. Also crystal hardness observation reveals that the hardness of KCl single crystal has been increased by adding different percentage of nanodiamond impurity. In addition, the study of FTIR spectrums of the pure and doped crystals represents that the KCl optical properties has not changed.

Epitaxial Crystal Growth and Solid-State Polymerization of Piperonyl Muconate on the {001} Surface of KCl Crystal for Controlling Polymer Chain Alignment

We investigated the crystal growth of piperonyl (E,E)-muconate [bis(3,4-methylenedioxybenzyl) (E,E)-muconate, MDO] on inorganic crystalline substrates during vapor deposition for the control of polymer chain alignment by the subsequent solid-state photopolymerization of the MDO monomer thin films deposited on the substrate. We controlled the arrangement of the MDO molecules and the polymer chains produced on the substrate, depending on the lattice parameters of the substrate surfaces used. The epitaxial crystal growth of MDO on the {001} plane of a KCl single crystal was observed under the condition that the crystal lattice lengths of MDO agreed well with the specific space distance of the substrate; i.e., the KCl cubic crystal resulted in a d(110) value of 4.45 Å, which was very close to the value of the monomer stacking distance in the MDO crystal (d(s) = 4.43 Å). On the other hand, slightly large and too small d(110) values for KBr and NaCl, respectively, resulted in the less controlled and no epitaxial crystal growth of MDO. The irradiation of polarized UV light on the MDO thin-film crystal produced highly regulated polymer alignment in a specific direction on the KCl substrate.

Luminescence studies on gamma irradiated KCl: Ce3+ crystals

This paper reports thermoluminescence(TL), optical absorption and TL emission studies that are made on Ce3+ doped KCl single crystals irradiated at room temperature. The glow curve and optical absorption studies indicate the participation of Ce3+ ions in the TL process. The TL study suggests the presence of low concentration of Ce3+ ions which reduces the TL efficiency with respect to pure KCl samples. On F bleaching γ irradiated crystals Z1 centers are observed. A broader and strongly intense violet blue emission at 290, 370, 423 and 488nm has been observed with 240nm excitation. This emission has been attributed due to the transition from 5d(2D) excited energy level to the 4f1 ground stable energy level (2F5/2 and 3F7/2) of Ce3+ doped KCl crystals.

Elaboration and Characterization of AuCl Semiconductor Nanocrystals Embedded in KCL Single Crystals

In this work, we investigated the structural and the optical properties of AuCl semiconductor nanocrystals embedded in KCl single crystals. The AuCl nanocrystals were obtained by doping the KCl crystalline matrix with gold using the Czochralski method. The X-ray diffraction showed the formation of the AuCl nanocrystals in KCl with a tetragonal structure. The average radius of the AuCl nanocrystals is estimated using the Scherrer formula. The photoluminescence spectra presented a band emission situated at 580 nm leading to the formation of the AuCl nanocrystals within KCl.

KCl Single Crystals Growth with Mn, Ag and In Impurities by Czochralski Method and Study of Impurities Influence on Their Properties

In this research KCl, KCl:Mn, KCl:Ag and KCl:In single crystals have been grown by Czochralski method. X-ray diffraction confirms KCl single crystal formation. In this work also influence of mentioned impurities on the optical property of KCl single crystal has been studied by chemical etching. Then the hardness of these crystals have been measured by Vickers micro hardness. The result indicate the positive effect of the impurity on optical and mechanical properties.

The effect of ultrasonic perturbation on F-centers in Kcl: A thermoluminescence study

Abstract The effects of high Frequency (HF) progressive ultrasonic wave on the F-centers in KCl single crystals are discussed in this paper. Ultrasonics of 3 MHz and 9 MHz are used in the present investigation to produce strain wave perturbation on the F-centers. The thermoluminescence (TL) glow curves obtained from X-irradiated normal and strain wave exposed KCl single crystals show two peaks. In the TL glow curves recorded from X-irradiation followed by the ultrasonic wave exposure of KCl single crystals result in the shift of these peaks to higher temperature side with an increase in their separation and a change in relative areas. However, no additional peaks were seen. Apart from this the strain wave perturbation was also found to effect trapping parameters.

Luminescence properties of KCl:Ag − crystals excited near the fundamental absorption edge

Luminescence properties of KCl single crystals doped with Ag − centers have been investigated under various excitation energies around the fundamental absorption edge at low temperatures. Under the excitation at 6.89 eV, which is lower than the intrinsic exciton energy by 0.87 eV, the A ′ luminescence band due to the intraionic transition in the Ag − ion is dominantly observed at 2.91 eV. On the other hand, the excitation at 6.66 eV induces a broad luminescence band at 2.60 eV in addition to the A ′ luminescence band. From the comparison with the localized excitons in KCl:I crystals, the 2.60 eV luminescence band is attributed to the two-center type localized exciton related with the Ag − ion. The adiabatic potential energy surfaces of the excited states in the Ag − center and the localized exciton in KCl:Ag − are discussed.

Interaction between dislocation and defects induced by X-irradiation in alkali halide crystals

Abstract Interaction between dislocation and defect induced by X-irradiation has been investigated in NaCl and KCl single crystals by strain rate cycling tests under superimposition of ultrasonic oscillation during plastic deformation. The interaction energy between dislocation and radiation-induced defect has been obtained by fitting Barnett model to experimental results, assuming that the defect is tetragonal. The interaction energies between dislocation and defect were determined to be 0.39 and 0.87 eV for NaCl and KCl, respectively. The larger interaction energy for KCl presents its larger tetragonality of defect induced by X-irradiation than NaCl.

Optical parameters of CaF2, LiF, NaCl and KCl single crystals in the X-ray spectral range

Optical parameters of CaF2, LiF, NaCl and KCl single crystals in the X-ray spectral range

ChemInform Abstract: Chemical Analysis of Photoassisted Intercalation Reaction of SnS2 Single Crystal Under Cathodic Polarization.

Abstract Cathodic reactions at (001) SnS2 single crystal—KCl aqueous solution were investigated analytically both in the dark and under illumination. Reductive decomposition of the SnS2 host occurred in the dark besides intercalation of the hydrated K+ ion. However, the former was inhibited by illumination.

Anisotropy of transient high-temperature bending creep of single crystals

The orientation dependence of the transient high-temperature creep rate of NaCl and KCl single crystals under nonuniform stresses is experimentally studied. The anisotropy of high-temperature bending creep of single crystals is ascertained by analyzing the distribution of bending stresses, the number of possible dislocations providing deformation, the reduced shear stresses causing sliding of dislocations, and the dislocation structure of single crystals after creep. It is shown that hindered dislocation sliding in the easy sliding system activates a new slip system at a certain temperature.

90SR IN MAMMAL TEETH FROM CONTAMINATED AREAS IN THE FORMER SOVIET UNION MEASURED BY IMAGING PLATES

Imaging plates sensitive to beta rays were used to obtain the images of 90Sr in tooth samples taken from mammals collected in contaminated areas of the former Soviet Union. The average concentrations of 90Sr in the samples were determined by comparing the intensities of the luminescence using a single crystal of KCl. The results showed that the determined 90Sr concentration has a positive correlation with the soil contamination levels in the South Ural region. Tooth samples from both inside of the Semipalatinsk nuclear test site and the villages nearby have detectable amounts of 90Sr, indicating the possible presence of residual soil contamination. The present study demonstrates that using imaging plates is a very sensitive method to detect 90Sr in teeth as well as to estimate low-level 90Sr contamination in soil.

Deformation luminescence of X-irradiated KCl:Eu2+ by bending test

It is well known that luminescence occurs during plastic deformation of X-irradiated alkali halide crystals. Luminescence pattern of KCl single crystals doped with europium has been observed during bending tests by using a CCD camera. Luminescence begins on both the fulcrum contact and opposite sides of a crystal at the beginning of plastic deformation. Several luminescence lines run along slip bands toward neutral axis from the outside of a sample in the direction of 45 degrees. Flash sometimes occurs both in the tension area and in the compression one. As deformation proceeds the luminescence lines are confused and right triangle-like luminescence pattern appears symmetrically on both sides of a central fulcrum in the compression area as well as in the tension one for three point bending tests. Strong flash has taken place in the triangle-like area just at fracture. But relatively homogeneous luminescence between two inner fulcrums has been observed for four point bending tests.

Plasma parameters at nanosecond breakdown and capillary discharge in a solid insulator

The subject of investigation is the energy-mass composition of a plasma resulting from the breakdown of KCl single crystals and from discharges in capillaries produced by the breakdown of KCl and high-pressure polyethylene samples. The plasma flux formed by the head of the discharge channel in KCl is found to be much less intense than the plasma flux due to the capillary and surface discharges. Also, the first breakdown of KCl does not produced multiply charged ions of the related material. It is revealed that the energies and charge numbers for the capillary and surface discharges are close to each other.

Macro- to Nano-indentation Hardness Stress–Strain Aspects of Crystal Elastic/Plastic/Cracking Behaviors

Single crystal KCl and MgO indentation hardness test results spanning macroscopic, microstructural, and nanoscale measurements are brought together in a ball-indenter-based stress–strain description. For a significant range of hardness measurements made on MgO (001) crystal surfaces, increasingly greater plastic flow stresses are determined at smaller loads applied to smaller effective ball sizes at the rounded tips of Berkovich indenters; and, at the smallest ball diameters of 3,200 nm and 400 nm, the plastic flow stresses are shown to approach the predicted Hertzian elastic loading stresses. The resultant hardness stress–strain description, that is extended to cover the elastic, plastic, and cracking behaviors of MgO crystals, is usefully applied also to a comparison of indentation test results reported for NaCl and RDX crystals. In general, the dislocation-induced cracking stress measurements are shown for MgO and RDX crystals to be lower than cracking stresses evaluated on an (elastic) indentation fracture mechanics (IFM) basis. Comparison is made with metal nanoindentation hardness test results.

Shock induced phase change in KCl single crystals: Orientation relations between the B1 and B2 lattices

The relative orientations between the lattices of the low pressure (B1) and high pressure (B2) phases of shock compressed KCl single crystals were examined using plate impact loading along the [111] and the [110] directions. The B2-phase lattice planes, perpendicular to the loading direction, were determined from transient x-ray diffraction measurements. Two closely spaced diffraction peaks were observed for the [111] loading direction. The lower Bragg angle peak is consistent with a 200 peak of a cubic B2-phase unit cell giving the orientation relation [111]B1 is parallel to [100]B2. The higher Bragg angle peak is not consistent with any peak from either a cubic B1 or a cubic B2 unit cell; the origin of this peak is unknown. Other experiments found no orientation relations; for the [111] loading direction, [111]B1 is not parallel to [211]B2 and for the [110] loading direction, [110]B1 is not parallel to [100]B2. The orientation relation determined for the [111] loading in this work is incompatible with a previously determined orientation relation obtained for the [100] loading [T. d’Almeida and Y. M. Gupta, Phys. Rev. Lett. 85, 330 (2000)]. This finding suggests that the transformation pathway between the B1 and B2 lattices in KCl crystals depends on the shock compression direction for the B1 phase. The results are discussed in terms of the compatibility between the macroscopic uniaxial strain imposed by shock wave loading and the microscopic rearrangement of atoms leading to the observed orientation relations.

Effect of microwave heating on diffusion in KCl–KBr single crystals

The interdiffusion in single-crystal KCl-KBr diffusion couples, which form continuous solid solutions, is examined under microwave heating (24 GHz). The results are compared with data obtained under conventional heating. Electron microprobe analysis is used to examine the composition of the diffusion zone and microscopic analysis is used to examine its microstructure. It is shown that ion interdiffusion occurs faster under microwave heating than under conventional heating. The ascending diffusion of Cl and Br ions is revealed under microwave heating. The microstructure of the diffusion zone between KCl and KBr single crystals is highly heterogeneous after microwave heating and markedly different from that after conventional heating.