Single Crystal Potassium Research Articles

A novel water-in-deep eutectic solvent microemulsions for chemical polishing of single crystal KDP

Microemulsion (ME) has been investigated as a chemical polishing (CP) fluid for effective polishing of single crystal potassium dihydrogen phosphate (KDP), perfectly avoiding the generation of mechanical stress. In this work, a water-in-deep eutectic solvent ME was proposed as the polishing fluid for CP of single crystal KDP. Deep eutectic solvent (DES) is formulated using n-octanol as hydrogen bond donor and methyltrioctylammonium chloride (MTOAC) as hydrogen bond acceptor, with a mass ratio of 2:1. The ME was prepared by mixing DES as the oil phase (12.5 %, wt.), a hydrochloric acid solution as the water phase (12.5 %, wt.), and isopropanol as the cosolvent (75 %, wt.), without adding any other surfactants. The properties of the ME were characterized by conductivity measurements and ultraviolet (UV) spectroscopy. The reactivity of ME with KDP was measured by the conductivity method, and it was higher at low pH values. A hydrochloric acid solution with a pH of 3 was selected as aqueous phase, considering its effects on particle size, salt loading, and static etching rate. The water content affects the polarity of ME and the final water content was determined to be 12.5 % to ensure high polarity of ME. The surface quality of the KDP crystals before and after polishing was examined using grazing incidence X-ray diffraction (GIXRD) analysis. The average roughness of the KDP crystal surface was decreased from 1.96 nm to 1.43 nm, and the root-mean-square (RMS) roughness was reduced from 2.81 nm to 1.86 nm, demonstrating a significant polishing effect. Finally, the polishing mechanism was elucidated in terms of the irreversible chemical reaction between the active components in the microemulsion and the KDP crystals.

Phonon Focusing and Electron Transport in Potassium Single Crystals. Review 2

Phonon Focusing and Electron Transport in Potassium Single Crystals. Review 2

Subsurface damage layer of bulk single-crystal potassium dihydrogen phosphate (KDP) after SPDT: studied by the grazing incidence X-ray diffraction technique

This work proposes a novel way of the subsurface damage layer characterization for bulk single-crystal optical material, based on the X-ray grazing incidence technique (GIXRD). The result shows that the subsurface damage layer of bulk single-crystal potassium dihydrogen phosphate (KDP) mainly consists of polycrystalline KDP and bulk single-crystal matrix after single-point diamond turning (SPDT). Meanwhile, it is found that the polycrystalline KDP presents some kinds of preferred orientations, which depend on the SPDT surfaces and SPDT track u . For example, the polycrystalline texture of (010) SPDT surface is p (103)// u and p (204)// u , while the polycrystalline texture of (111), I-type and II-type SPDT surfaces are p (312)// u , p (332)// u and p (202)// u , respectively. These findings allow us to further understand the subsurface damage layer of bulk single-crystal KDP after SPDT.

Effect of Phonon Focusing on the Drag Thermopower in Single-Crystal Potassium Nanowires at Low Temperatures

The role of shear waves and the effect of phonon focusing on the anisotropy of the thermopower of the electron–phonon drag in single-crystal potassium nanowires at low temperatures are analyzed in this work. The deformation potential theory is used for the longitudinal components of elastic modes. For the shear components of vibrational modes, the electron–phonon interaction constant is used, which was determined previously from comparing the results of calculating the thermoelectric power with experimental data for bulk potassium crystals. It is shown that shear waves make a significant contribution to the drag thermopower of nanowires. In the regime of the Knudsen phonon gas flow for nanowires with a cross-section side D = 5 × 10–6 cm, the contribution of the slow transverse mode t2 with allowance for only the longitudinal component in the [111] directions turned out to be 32% smaller and, with allowance for the shear component of the t2 mode, 12% greater than the contribution of longitudinal phonons. Directions corresponding to the maximum and minimum values of the drag thermopower of nanowires are determined. It is shown that, under conditions of competition between the boundary and bulk mechanisms of phonon relaxation with an increase in the cross section of nanowires, the anisotropy of the drag thermopower changes nonmonotonically. It exceeds 30% not only in the Knudsen phonon gas flow regime, but also when the sample thickness is two orders of magnitude greater. This makes the anisotropy of thermopower available for experimental studies.

Epitaxial Stabilization of Tetragonal Cesium Tin Iodide.

A full range of optoelectronic devices has been demonstrated incorporating hybrid organic-inorganic halide perovskites including high-performance photovoltaics, light emitting diodes, and lasers. Tin-based inorganic halide perovskites, such as CsSnX3 (X = Cl, Br, I), have been studied as promising candidates that avoid toxic lead halide compositions. One of the main obstacles for improving the properties of all-inorganic perovskites and transitioning their use to high-end electronic applications is obtaining crystalline thin films with minimal crystal defects, despite their reputation for defect tolerance in photovoltaic applications. In this study, the single-domain epitaxial growth of cesium tin iodide (CsSnI3) on closely lattice matched single-crystal potassium chloride (KCl) substrates is demonstrated. Using in situ real-time diffraction techniques, we find a new epitaxially-stabilized tetragonal phase at room temperature that expands the possibility for controlling electronic properties. We also exploit controllable epitaxy to grow multilayer two-dimensional quantum wells and demonstrate epitaxial films in a lateral photodetector architecture. This work provides insight into the phase control during halide perovskite epitaxy and expands the selection of epitaxially accessible materials from this exciting class of compounds.

Effects of dyes in the growth, optical, mechanical and dielectric properties of KDP crystals

One among the prominent single crystal potassium dihydrogen phosphate (KDP) was grown by slow evaporation solution technique and also doped with three organic dyes like Alizarin, Congo red and Evans blue. The cell parameters of the pure and doped KDP crystals were found using powder x-ray diffraction. The optical behavior of the pure and doped KDP crystals was analyzed through the UV–Visible absorption spectrum. The functional group analysis of the grown crystals was done using FT-IR spectral study. The emission characteristics of the pure and doped KDP were found using photoluminescence study which results in multicolored emission spectra. The second harmonic generation of the pure and doped KDP crystals shows better frequency conversion property of the crystals. The laser damage threshold (LDT) study was done for all the grown crystals and the results were compared. The growth pattern of the pure and dye doped KDP crystals were examined using etching analysis. The mechanical stability of the grown crystals was determined using Vicker’s microhardness study. The dielectric property of pure and dye doped KDP crystals are carried out at room temperature for different frequencies.

Enhanced physical properties of potassium zinc sulphate hydrate single crystal following iodide doping

The crystal grown from mixing potassium iodide and zinc sulphate in an aqueous solution was found to be a single crystal potassium zinc sulphate hydrate. The iodide ions enter the crystal matrix as a dopant with small ratio. The evaluation of the crystal structure was achieved by single crystal diffraction and the resolved structure was monoclinic with space group P21/c. The effect of iodide doping is observed in the crystal morphology and the x-ray powder diffraction pattern. The iodide ions were detected in the grown crystal using x-ray fluorescence and energy dispersive x-ray which spotted a very small fraction of iodide in the raw materials of the crystal. The iodide doping also affected the thermal stability of the original crystal and introduced different thermal behavior. The optical properties are also affected and a noticeable band in the transmittance is observed. The iodide effect on the structure of optical energy gap is analyzed using photoluminescence spectra. Second harmonic generation test shows an unexpected behavior based on the structure of the grown crystal.

Fabrication and analysis of single-crystal KTiOPO₄ films with thicknesses in the micrometer range.

Single-crystal potassium titanyl phosphate (KTiOPO4, KTP) films with thicknesses less than 5 μm are obtained by using helium (He) implantation combined with ion-beam-enhanced etching. A heavily damaged layer created by a 4×10(16) cm(-2) fluence of 2 MeV He implantation is removed by means of wet chemical etching in hydrofluoric acid (HF). Thus, free-standing films of KTP with thicknesses in the range of 3-5 μm are obtained. The etching rate can be adjusted over a wide range by choosing temperature and HF concentration, as well as annealing conditions. Sharp etching edges and the smooth surface of the film indicate that a high selective-etching rate is achieved in the damaged layer, and the remaining part of the crystal is undamaged. X-ray and Raman-scattering results prove that KTP films have good single-crystal properties.

Growth and characterization studies of a new NLO single crystal potassium l-asparaginate

Potassium l-asparaginate (PLA) is a new semiorganic NLO material of amino acid family. In this work, we have grown PLA single crystal by slow evaporation method. The lattice parameters were calculated from single crystal XRD data. XRD analysis yielded a space group of P21 with lattice parameters a=10.470Å, b=8.839Å, c=12.808Å, α=β=90°≠γ, volume=1185.30Å3. Solubility studies were made at different temperatures with various solvents. The solubility was found to be 17g in 100ml of water at room temperature. The functional groups present in the grown sample were identified from the vibrational frequencies of the recorded FTIR spectrum. UV–vis-NIR spectrum of PLA crystal shows the cut off wavelength of the crystal to be at 230nm. The second harmonic generation efficiency of PLA single crystal estimated using Kurtz and Perry method. The nature of variation of dielectric constant (ɛr) and dielectric loss (D) with frequency at different temperatures were investigated. The AC conductivity measurements done on PLA reveal that PLA crystal has a sharp electrical conductivity with an increase of temperature.

2D modeling of regeneration surface growth on a single-crystal sphere

This paper investigates the evolution of a sphere produced from a single crystal potassium alum in course of its regeneration, using numerical 2D-simulation in the kinematic model, which describes the growth of the regenerating surfaces.The modeling results demonstrate a qualitative agreement between the predictions of the kinematic model and real processes of sphere regeneration. It is shown that the face arising on the regenerating surface of a sphere may grow either more slowly or more rapidly than the surrounding surface. In the latter case, the face interacts with the regeneration surface and disappears from the sphere surface before intersecting in edges with neighboring faces. The influence of the input model parameters on the numerical modeling results is analyzed. It is established that the roughness parameters of the initial surface of a single-crystal sphere significantly affect the surface evolution during regeneration.

Domain-orientation-controlled potassium niobate family piezoelectric materials with hydrothermal powders.

Materials of the potassium niobate family, as lead-free piezoelectric materials, are expected to be alternative materials to Pb(Zr,Ti)O3 (PZT) because of their good piezoelectric properties, high Curie temperature, and so on. In particular, single-crystal potassium niobate is a promising ferroelectric material as a surface acoustic substrate and for functional optical effects. It is, however, well known that single crystals are difficult to fabricate because of the instability caused by temperature, external stress, and other factors.

Crystal growth of KPb2Cl5 by Bridgeman method with pressure control system

Abstract ⊙15 mm Single crystals of potassium lead chloride (KPb2Cl5) have been grown by a novel modified Bridgman method under protect of N2 and CCl4 with a pressure control system. It could make vacuum or protect atmosphere according to the need of raw materials composition and crystals growth. So the process of preparation of crystal would be simplified. Measurements of the transmission of crystal in the mid-infrared were also made.

Young’s modulus and fracture during Knoop indentation of potassium, rubidium, cesium, and ammonium acid phthalate single crystals on the (010) plane

The correlation of the anisotropy of the Young’s modulus of organic single crystals of potassium, rubidium, cesium, and ammonium acid phthalates with strain and fracture patterns during Knoop indentation on the (010) cleavage plane in the [001] and [100] directions has been studied. The data on the maximum anisotropy of the strain and fracture patterns of the ammonium acid phthalate single crystal have been discussed in view of the published data on the structure, mechanical, elastic, and X-ray spectral properties of these crystals.

Emission of Negative Potassium Ions from Single Crystal Potassium Bromide during Exposure to 248-nm Excimer Laser Radiation

Many wide bandgap materials yield charged and neutral emissions when exposed to sub-bandgap laser radiation at power densities below the threshold for optical breakdown and plume formation. In previous work, we reported the observation of negative alkali ions from several alkali halides under comparable conditions. Within our detection sensitivity, we observed no negative halogen ion emission, in spite of the high electron affinities of the halogens. Significantly, the positive and negative alkali ions showed a high degree of spatial and temporal overlap. Our conclusion, based on a detailed study of KCl emissions, was that K− is formed by the sequential attachment of two electrons to K+. Here we provide further evidence for this mechanism based on a study of KBr.

Manipulating mechanics and chemistry in precision optics finishing

abstractDeterministic processing is critical to modern precision optics finishing. Put simply, determinism is the ability to predict an outcome before carrying out an activity. With the availability of computer numerically controlled (CNC) equipment and sophisticated software algorithms, it is now possible to grind and polish optics from a variety of materials to surface shape accuracies of ∼20 nm peak-to-valley (p–v), with surface roughness values (measured on white light interferometers over 250 μm 350 μm areas) to sub-nm root-mean-square (rms) levels. In the grinding phase the capability now exists to estimate removal rates, surface roughness, and the depth of subsurface damage (SSD) for a previously unprocessed material, knowing its Young’s modulus, hardness, and fracture toughness. An understanding of how chemistry aids in the abrasive-driven removal of material from the surface during polishing is also critical. Recent polishing process research reveals the importance of chemistry, specifically slurry pH, for preventing particle agglomeration in order to achieve smooth surface finishes with conventional pad or pitch laps. New sub-aperture polishing processes like magnetorheological finishing (MRF) can smooth and shape flat, spherical, aspheric and free-form surfaces within a few process iterations. Difficult to finish optical materials like soft polymer polymethyl methacrylate, microstructured polycrystalline zinc sulfide, and water soluble single-crystal potassium dihydrogen phosphate (KDP) can be finished with MRF. The key is the systematic alteration of MR fluid chemistry and mechanics (i.e. the abrasive) to match the unique physical properties of each workpiece.

Measurement of Dielectric Parameters of Small Samples at X-Band Frequencies by Cavity Perturbation Technique

The cavity perturbation method has been used to measure the permittivity of various dielectric materials such as Teflon, alumina, silica fiber, single crystal potassium chloride, bakelite, and p-type silicon at X-band frequencies. Normally, the samples required for measurements in a rectangular cavity are in the form of thin slabs/rods of height at least equal to the height of the cavity. When available samples are smaller (smaller than the height of the cavity), accurate measurements are often difficult. In this paper, an easy and reliable method is discussed for accurate determination of the properties of small-sized samples.

Electromagnetic characterization of rectangular ferroelectric resonators

An optimized geometry for a rectangular ferroelectric resonator (FR) is proposed to increase signal-to-noise ratio in EPR spectroscopy. To develop optimization criteria, the distribution of the microwave electromagnetic field in the FR is computed and analyzed. The computations, based on solution of Maxwell’s field equations, were made for two types of rectangular FRs—a FR with a hollow sample hole and a FR with a blind sample hole. To introduce the samples, a hole was drilled through the resonator with its axis aligned to the axis of the FR. We computed and studied the spatial distributions of H- and E-components of the microwave electromagnetic field for two rectangular FRs, made of single-crystal potassium tantalate, with the following sizes: 1.9 × 1.9 × 1.4 mm 3 and 1.7 × 1.7 × 3.1 mm 3. As analysis of the obtained data indicated, in both resonators, the lowest mode was TE 11 δ . By analyzing the distribution of the microwave field in the FR and comparing it with the experimental result, we developed optimization criteria for the geometry of a rectangular FR.

Investigation of the slip geometry of high-purity potassium by in situ X-ray diffraction

Abstract Plastic deformation of bcc metals at intermediate and low temperatures is dominated by [1 1 1] screw dislocations which macroscopically seem to glide on planes of high or irrational Miller indices. It is now well established that this non-crystallographic glide is composed of elementary steps of kink-pair formation on three symmetry-equivalent low-index planes. In the present investigation, the slip geometry of high-purity potassium single crystals was investigated by in situ X-ray measurements of the lattice rotation in uniaxial compression in the temperature range from 6 to 70 K. The different alternatives for the elementary glide planes, e.g., {1 1 0}, {2 1 1} or {3 2 1}, can be uniquely distinguished from changes of the primary slip direction within the unit triangle. The results showed that the elementary glide step in potassium occurs on {2 1 1} planes in the investigated temperature range. In addition, glide of [1 0 0] dislocations (obviously products from interactions between mobile and sessile [1 1 1] dislocations) becomes dominating in many samples at increasing plastic strain. Numerical simulations of the orientation change in 〈1 1 1〉{2 1 1} glide, based on the model of thermally activated kink-pair formation, were in good agreement with the experimental results.

Low-loss crystal-ion-sliced single-crystal potassium tantalate films

The dielectric response has been studied in 10-μm-thick, single-crystal potassium tantalate films formed by crystal ion slicing. Scanning microwave microscopy shows that the implanted, pre-etched samples exhibit a bulk-like permittivity and low-loss tangent (0.0009) at 1.7 GHz. The separated free-standing films have somewhat higher loss tangents due to residual-ion-induced stress. Selective relaxation of this stress by etching or annealing reduces the dielectric loss.

Metallography of alkali metal single crystals

The paper discusses methods for metallographic preparation of lithium, sodium and potassium single crystals. Because mechanical techniques and electropolishing cannot be applied, chemical polishing methods in organic solvents are considered in detail. A few methods suggested earlier in the literature were re-examined. Improved techniques were developed that yield an excellent metallographic surface quality for optical microscopy and scanning electron microscopy. First results of in situ optical microscopy investigations of the low-temperature phase transformation of lithium and of in situ slip line investigations in all three metals are shown.