Pyramidal Growth Sectors Research Articles

Effect of sunset yellow dye on morphological, optical, dielectric, thermal and mechanical properties of KDP crystal

Herein, we describe the growth and morphology of well-defined dyed crystals of KH2PO4 (potassium dihydrogen orthophosphate; KDP) containing organic azo (sunset yellow; SSY) dye in the {1 0 1} & {0 0 1} pyramidal growth sectors. An understanding on selective dye inclusion in various growth sector of host crystal is proposed, which will help in designing novel tailor-made dyed photonic crystals. The structural analysis and the identification of various functional groups present in as grown KDP crystals were carried out using powder XRD, FTIR and Raman studies. Solid state transmittance spectra for dyed KDP crystals displayed three absorption peaks at 230 nm, 311 nm and 477 nm, which were blue shifted for SSY dye in KDP crystal relative to neutral aqueous solution of SSY dye. These blue shifts in the absorption maxima confirm the successful incorporation of sunset yellow dye into the pyramidal growth sectors of dyed KDP crystals. The band around 409 nm in the photoluminescence emission spectrum indicates a violet emission. SSY dye doped KDP crystals showed enhanced dielectric properties and thermal stability as compared to pure KDP crystal. The mechanical strength of the KDP crystals estimated using Vickers microhardness test was found to decrease with the increase in SSY dye doping.

Relaxation Kinetics of the Microhardness of KDP Crystals after Their Exposure to a Magnetic Field

It has been shown that potassium dihydrogen phosphate crystals change their microhardness reversibly after their exposure to a magnetic field of B = 0.8 or 1.2 T for tm = 7–90 min. It has been found that the magnetic effect can be conveniently characterized by the quantity B2tm, because the variation of the parameters conserving B2tm=const does not change the result. At B2tm < 10 T2 min, the effect is almost absent. Above this threshold, the amplitude of changes in the microhardness increases and approaches a constant value of ~10% at B2tm ≈ 19 T2 min. The responses of samples of the same crystal from the faces of the prismatic and pyramidal growth sectors to exposure are different. In the former case, they soften; in the latter case, the hardening stage follows the softening stage. However, in both cases, the microhardness returns to the initial value. At B2tm values from 19 to 37 T2 min, the amplitudes and durations of the effect do not change, but in the narrow range of 37–43 T2 min, the lifetime of the modified state increases sharply with transition to a new level: “sharp” peaks with a half-width of ~2 days are transformed to trapezoids with the width of the horizontal side of ~1–2 weeks. A physical scheme of the observed effects has been proposed.

KH2PO4 single crystals activated with the Ti4+ ions in the form of TiO2−x × nH2O nanoparticles: Structural peculiarities, point defects, and dielectric properties

Potassium dihydrogen phosphate KH2PO4 (KDP) single crystals activated with Ti4+ ions in the form of TiO2−x × nH2O nanoparticles in the η-phase, synthesized by the sulfate method using TiOSO4 × хH2SO4 × yH2O, have been first grown by the temperature lowering method and cut from pyramidal (P) and prismatic (Pr) growth sectors. The first-performed neutron powder diffraction investigation of P and Pr samples cut from the KDP:Ti4+ crystal allowed us to reveal vacancies in the K and H sites for both samples, their number being larger in the Pr structure compared to the P one. Taking into account the deficiency of the K and H sites, full occupation of the O site, presence of Ti4+ ions in the structure, and the electroneutrality condition, a partial substitution of (PO4)3− anion by the (SO4)2− one, larger for the Pr sample, was observed. The real compositions of P and Pr samples, correlated with the cation-anion internuclear distances, were refined. The dielectric permittivity of the Pr sample was significantly lower than that of the P one; it decreases with decreasing К–O, P–O, and O···H distances and increasing deficiency of the K and H sites.

Carbocernaite from Bear Lodge, Wyoming: Crystal chemistry, paragenesis, and rare-earth fractionation on a microscale

Zoned crystals of carbocernaite occur in hydrothermally reworked burbankite-fluorapatite-bearing calcite carbonatite at Bear Lodge, Wyoming. The mineral is paragenetically associated with pyrite, strontianite, barite, ancylite-(Ce), and late-stage calcite, and is interpreted to have precipitated from sulfate-bearing fluids derived from an external source and enriched in Na, Ca, Sr, Ba, and rare-earth elements (REE) through dissolution of the primary calcite and burbankite. The crystals of carbocernaite show a complex juxtaposition of core-rim, sectoral, and oscillatory zoning patterns arising from significant variations in the content of all major cations, which can be expressed by the empirical formula (Ca 0.43–0.91 Sr 0.40–0.69 REE 0.18–0.59 Na 0.18–0.53 Ba 0–0.08 ) ∑1.96–2.00 (CO 3 ) 2 . Interelement correlations indicate that the examined crystals can be viewed as a solid solution between two hypothetical end-members, CaSr(CO 3 ) 2 and NaREE(CO 3 ) 2 , with the most Na-REE-rich areas in pyramidal (morphologically speaking) growth sectors representing a probable new mineral species. Although the Bear Lodge carbocernaite is consistently enriched in light REE relative to heavy REE and Y (chondrite-normalized La/Er = 500–4200), the pyramidal sectors exhibit a greater degree of fractionation between these two groups of elements relative to their associated prismatic sectors. A sample approaching the solid-solution midline [(Ca 0.57 Na 0.42 ) ∑0.99 (Sr 0.50 REE 0.47 Ba 0.01 ) ∑0.98 (CO 3 ) 2 ] was studied by single-crystal X-ray diffraction and shown to have a monoclinic symmetry [space group P 11 m , a = 6.434(4), b = 7.266(5), c = 5.220(3) A, γ = 89.979(17)°, Z = 2] as opposed to the orthorhombic symmetry (space group Pb 2 1 m ) proposed in earlier studies. The symmetry reduction is due to partial cation order in sevenfold-coordinated sites occupied predominantly by Ca and Na, and in tenfold-coordinated sites hosting Sr, REE, and Ba. The ordering also causes splitting of carbonate vibrational modes at 690–740 and 1080–1100 cm −1 in Raman spectra. Using Raman micro-spectroscopy, carbocernaite can be readily distinguished from burbankite- and ancylite-group carbonates characterized by similar energy-dispersive spectra.

Nonlinear optical response of nanocomposites based on KDP single crystal with incorporated Al2O3*nH2O nanofibriles under CW and pulsed laser irradiation at 532 nm

Optical properties and nonlinear optical response due to the CW and pulsed laser radiation self-action at 532nm were studied in composites based on KDP single crystals with incorporated nanofibriles of nanostructured oxyhydroxide of aluminum (NOA). It was shown a high optical quality and structural homogeneity of nanocomposites KDP:NOA by the transmittance spectra, elastic optical scattering and XRD analysis. It was observed manifestation of the second harmonic generation efficiency enhancement in the KDP:NOA versus the nominally pure KDP (λ=1064nm, τ=1ns) that is correlated with efficient refractive index self-modulation Δn∼10−4 (λ=532nm, τ=30ps). In the pyramidal and prismatic growth sectors of the nominally pure KDP crystal it was shown opposite signs of the photoinduced variations both of the refractive index and of the optical absorption/bleaching due to resonant excitation of the native defects at 532nm. It should be considered for the wide-aperture laser frequency KDP family based convertors fabrication.

Growth, structure peculiarities, and dielectric properties of ferroelectric KDP/TiO2 single crystals

Potassium dihydrogen phosphate KH2PO4 (KDP) single crystals, both pure and with incorporated titanium dioxide TiO2 nanoparticles, are ferroelectric materials with dipole structure used in nonlinear optics, optoelectronics, and acoustooptics. To date, a comprehensive analysis of structural features and defect states in the KDP and KDP/TiO2 matrix is absent in literature data. Pure KH2PO4 (KDP) single crystals and KDP/TiO2 crystals with different TiO2 nanoparticles with anatase structure, synthesized by the sulfate and chloride methods, and with η-TiO2 structure, prepared by the sulfate method, grown by the temperature lowering method and cut from the pyramidal and prismatic growth sectors, have been investigated by the X-ray diffraction methods and by EDX spectroscopy. According to the energy-dispersive X-ray microanalysis, the sulfur content is higher in the sample with η-TiO2 and in the KDP/η-TiO2 crystal if compared with the samples with anatase and KDP/TiO2 (anatase). It was revealed that the sulfur content is higher in the prismatic growth sector if compared with the pyramidal one. Based on results of the X-ray single-crystal diffraction analysis, it is possible to assume the substitution of \( \text{PO}_{4}^{3 - } \) tetrahedra by \( \text{SO}_{4}^{2 - } \) ones in the KDP/TiO2 structures, which is greater in KDP/η-TiO2. The general composition of the KDP/η-TiO2 crystal from the prismatic growth sector with the highest titanium content can be written as \( (\text{K}_{0.950(1)} \square_{0.050} )\text{Ti}_{0.052\left( 2 \right)i} \left( {\text{H}_{2 - x}^{1 + } \square_{x} } \right)\left[ {\left( {\text{PO}_{4} } \right)_{y}^{3 - } \left( {\text{SO}_{4}^{2 - } } \right)_{1 - y} } \right] (\square \text{ - vacancies}). \) It was first found that the Ti4+ ions occupy the interstitial site (−0.048, 0.045, 0.550) in the KDP crystal matrix. Analysis of frequency-dependant dielectric characteristics revealed that the incorporation of TiO2 nanoparticles reduces the dielectric permittivity values of KDP/TiO2 samples compared with the pure KDP ones. It was found that the KDP/η-TiO2 sample has the smallest value of the dielectric permittivity.

Investigations of structural defects, crystalline perfection, metallic impurity concentration and optical quality of flat-top KDP crystal

KDP crystal grown using flat-top technique has been characterized using X-ray and optical techniques with the aim of correlating the defects structure and impurity concentration in the crystal with its optical properties. Crystallographic defects were investigated using X-ray topography revealing linear and arc like chains of dislocations and to conclude that defects do not originate from the flat-top part of the crystal. Etching was performed to quantify dislocation defects density. The crystalline perfection of the crystal was found to be high as the FWHM of the rocking curves measured at several locations was consistently low 6–9arcs. The concentration of Fe metallic impurity quantified using X-ray fluorescence technique was approximately 5 times lower in the flat-top part which falls in pyramidal growth sector as compared to the region near to the seed which lies in prismatic sector. The spectrophotometric characterization for plates cut normal to different crystallographic directions in the flat-top potassium dihydrogen phosphate (FT-KDP) crystal was performed to understand the influence of metallic impurity distribution and growth sectors on the optical transmittance. The transmittance of the FT-KDP crystal at 1064nm and its higher harmonics (2nd, 3rd, 4th and 5th) was determined from the measured spectra and the lower transmission in the UV region was attributed to increased absorption by Fe metallic impurity at these wavelengths. The results are in agreement with the results obtained using X-ray fluorescence and X-ray topography. Birefringence and Mach–Zehnder interferometry show that except for the region near to the seed crystal the optical homogeneity of the entire crystal was good. The laser-induced damage threshold (LDT) values are in the range 2.4–3.9GW/cm2. The LDT of the plate taken from the flat-top region is higher than that from the bottom of the crystal, indicating that the flat-top technique has good optical quality and is comparable to those reported using rapid growth technique. The results indicate that the structural defects, crystalline quality and impurity concentration have a correlation with the optical properties of the FT-KDP crystal.

Defects and Their Distribution in KH2PO4 Crystals with Embedded TiO2 Nanoparticles

ABSTRACTResults from the successful growth of high quality KH2PO4 (KDP) crystals with incorporated TiO2 anatase nanoparticles and the characterization of these crystals using several complementary methods are presented. Transmission and scanning electron microscopy have shown that the anatase nanoparticles were captured mainly by the pyramidal growth sector and, to a considerably lesser extent, by the prismatic growth sector. Energy dispersive x-ray analysis confirms that the growth layer stacks contain the TiO2 particles. Significant variation in the imaginary and real parts of the cubic nonlinear optical susceptibilities and refractive index changes at continuous wave excitation were found in prism and pyramid parts of pure KDP and KDP:TiO2 samples. The identified lines of electron paramagnetic resonance belong to four different centers FeA3+, FeB3+, CrR3+ and CrGB3+. From analysis of line intensities it was concluded that the concentration of non-controlled impurities in nominally pure KDP samples is several times larger than in KDP:TiO2, and that the concentration of non-controlled impurities in the prismatic part of the KDP:TiO2 boule is larger than in the pyramidal part.

Photoluminescence characterization of KH₂PO₄ crystal: application to three-dimensional growth-sector identification.

In this work, rapidly grown KH2PO4 (KDP) crystals extracted from the prismatic and the pyramidal growth sectors of crystal boules were analyzed using photoluminescence measurements. From the spectra, we deduced a robust criterion to discriminate between both growth sectors in an unknown KDP plate. Moreover, spatially resolved photoluminescence was shown to enable a local probing of different planes in the bulk of the material leading to accurate and nondestructive three-dimensional mapping of the sector boundary, which is often the weakest point in terms of laser-damage resistance in rapidly grown KDP crystals.

Optical properties of KDP crystals doped with pyrenetetrasulfonic acid salt

KDP crystals with incorporated molecules of the luminophore 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt (SPA) were grown from KH2PO4 solutions by the temperature lowering method. The luminescence spectra of KDP/SPA crystals and SPA solutions in distilled water and in KH2PO4 solutions, were studied. The increase of the dye content gives rise to excimer luminescence in the solutions and in KDP crystals, which is due to the formation of associated dye molecules. SPA molecules possessing negative electrostatic potential are incorporated into the pyramidal growth sector of KDP crystal.

Macroscopic and microscopic defects and nonlinear optical properties of KH2PO4 crystals with embedded TiO2 nanoparticles

Results from the successful growth of high quality KH2PO4 (KDP) crystals with incorporated TiO2 anatase nanoparticles and the characterization of these crystals using several complementary methods are presented. The study allowed the nature and distribution of macroscopic and microscopic defects in the KDP:TiO2 crystals to be clarified. The relationship between these defects and the distribution of TiO2 nanoparticles, and the influence of incorporated nanoparticles on the nonlinear optical properties of composite crystals in comparison with pure crystals were also elucidated. Visual observations, transmission and scanning electron microscopy have shown that the anatase nanoparticles were captured mainly by the pyramidal growth sector and, to a considerably lesser extent, by the prismatic growth sector. Energy dispersive x-ray analysis was able to confirm that the growth layer stacks contain the TiO2 particles. Fourier transformation infrared spectra have clearly shown the presence of an absorption band at about 800 cm−1 in both KDP:TiO2 and TiO2, and the disappearance of the band, associated with hydroxyl OH− groups on the TiO2 surface in KDP:TiO2. Significant variation in the imaginary and real parts of the cubic nonlinear optical susceptibilities and refractive index changes at continuous wave excitation were found in prism and pyramid parts of pure KDP and KDP:TiO2 samples. Deciphering complicated electron paramagnetic resonance spectra in KDP:TiO2 and comparison with published data permitted the identification of paramagnetic defects along with their associated g-factors and zero-field splitting parameters (in some cases for the first time). It was found that the dominant lines belong to four different centers FeA3+, FeB3+, CrR3+, and CrGB3+. From analysis of line intensities it was concluded that the concentration of intrinsic defects like potassium and hydrogen vacancies in KDP:TiO2 is comparatively small, that the concentration of non-controlled impurities in nominally pure KDP samples is several times larger than in KDP:TiO2, and that the concentration of non-controlled impurities in the prismatic part of the KDP:TiO2 boule is approximately twice as large as in the pyramid part.

Chemical and growth zoning in trapiche tourmaline from Zambia — a re-evaluation

Trapiche tourmalines from Zambia show the hexagonal prism a {112 - 0}, the positive pyramids r {101 - 1} and o {022 - 1} and the negative pyramid -r {011 - 1 } as dominant external crystal forms. The trapiche pattern is formed by the positioning of liquid and solid inclusions which are trapped at growth boundaries between pyramidal and prismatic growth sectors. Growth-induced elongate voids are also formed perpendicular to the dominant growth faces, which are inclined at 27°, at 46° or at 90° to the pedion {0001} of the tourmaline hosts. All the trapiche tourmalines are chemically zoned with isomorphic substitutions of Ca by Na and Mg by Al, which is characteristic for tourmalines of the uvite-dravite solid solution series. Content of Na increases and of Ca decreases from core to rim of all tourmalines. However, at the boundaries between different growth sectors (forming the geometric trapiche pattern of the samples), tourmaline compositions with higher Na and lower Ca contents than measured in adjacent pyramidal and prismatic growth sectors were found. The formation of this complex structural and chemical pattern is consistent with the formation of the tourmaline crystals in a two step process, with the skeletal growth of a sodium-rich dravite in a fi rst step and the subsequent, layer-by-layer growth of a second tourmaline generation. The growth of the second generation started with calcium-rich fl uor-uvite and was followed step-by-step by a more sodium-rich dravite. The green coloration of the samples is caused by minor contents of vanadium and chromium.

Structural features of the KH2PO4: Cr single crystal

The precision X-ray structural investigation of KH2PO4 (KDP) crystal samples from different growth sectors of a single crystal containing chromium impurities is performed. It is demonstrated that the structure of the sample from the prismatic growth sector is more perfect than the structure of the sample from the pyramidal growth sector. The impurity trapping can lead to the formation of at least four different types of structural defects on the face of the pyramid, whereas only two of them can be formed on the face of the prism. A comparison with the relevant data for the “pure” KDP crystal shows that the number of defects and their character are approximately identical for all samples. The analysis of the IR spectra indicates that nitrate ions are contained in the samples from both growth sectors. Moreover, structurally bound water molecules and OH groups are revealed in the sample from the prismatic sector.

Doping of KDP single crystals with cerium: Growth and optical properties

The features of doping of KDP crystals with cerium ions and organocerium complexes with alizarin complexon and arsenazo III have been investigated. It is established that “direct” doping by introducing cerium salts into the initial solution cannot be implemented. The effect of organometallic complexes of cerium on the crystal growth has been studied. Organocerium complexes predominantly enter the prismatic or pyramidal growth sectors. It is shown that the complex arsenazo III + Ce blocks the growth of the prismatic sector. Cerium-doped KDP crystals exhibit a photoluminescence band peaking at the wavelength λmax= 350 nm.

Effect of organic dyes on the dielectric properties of KH2PO4 crystals

The effect of organic dyes on the dielectric properties of KH2PO4 (KDP) crystals is studied over a wide range of temperatures. The dielectric properties of KDP crystals doped with molecules of the Chicago Sky Blue and Amaranth organic dyes are investigated for the first time. The dye molecules can be incorporated into the crystal lattice of KDP and selectively paint the pyramidal growth sectors of the crystal. The influence of dye organic impurities on the domain contribution to the permittivity is analyzed with due regard for the sectoral crystal structure. It is demonstrated that, upon doping of KDP crystals with organic dyes, the blocking effect of background impurities on domain walls is substantially weakened in the prismatic growth sector of the crystal in the polar phase. This leads to a noticeable change in the dielectric properties, specifically to an increase in the domain contribution to the permittivity of the crystal.

Refinement of the atomic structure of specimens cut out from different growth pyramids of a K(H0.052D0.948)2 PO4 single crystal

The structures of two crystalline specimens cut out from the pyramidal and prismatic growth sectors of a K(H0.052D0.948)2PO4 single crystal have been studied by diffuse neutron scattering and precision diffuse X-ray scattering. Diffuse scattering is concentrated in the vicinity of the Bragg reflections and is practically the same in specimens cut out from different growth sectors of a single crystal. X-ray diffraction analysis using the extinction parameters provided the establishment of a higher perfection of the specimen cut out from the prismatic growth sector. The precision X-ray studies revealed different configurations of hydrogen bonds in the specimens.

Influence of impurities on protein crystal perfection

A quasi-planar X-ray study has been done to assess the quality of crystals of pure thaumatin and of hen egg-white lysozyme as well as of lysozyme which was intentionally contaminated by structurally unrelated (ovalbumin and conalbumin) or related (turkey egg-white lysozyme) macromolecules. To investigate the behavior of different growth sectors, we have chosen crystals exhibiting well defined habit, namely crystals grown either in agarose gel or in silica gel. The main defect evidenced is a misorientation originating at the level of the nucleus: the parts grown in the + c and − c directions seem to be individuals twisted always clockwise with respect to the growth direction. The measured lattice plane tilt increases up to 3.5 min of arc when the contaminant content increases. In addition to this defect, we could measure for lysozyme relative lattice parameters differences (Δ d/ d) of the order of 10 −4 between prismatic and pyramidal growth sectors. All these defects do not seem to have a major influence on the resolution limit but they have consequences on optical properties.

Flux growth and characterization of the relaxor-based Pb[(Zn 1/3Nb 2/3) 1− xTi x]O 3 [PZNT] piezocrystals

Relaxor ferroelectric-based single crystals (1− x)Pb(Zn 1/3Nb 2/3)O 3– xPbTiO 3 [PZNT] ( x=0 and 0.09) were grown from high temperature solutions, using PbO or PbO/δB 2O 3 as flux. The optimum flux compositions and concentrations were found to be 50 wt.% PbO and (49 wt.% PbO+1 wt.% B 2O 3). It has been shown that addition of up to 1 wt.% B 2O 3 can stabilize the perovskite phase and improve the effectiveness of the flux. The optimum thermal profile consists of a soaking temperature at 1100°C and a gradually increasing cooling rate from 2 to 5°C min −1. The spontaneous nucleation process could be significantly modified by top-seeding technique. The crystal morphology was studied and related to a layer growth mechanism controlled by two-dimensional growth, and to the formation of pyramidal growth sectors. The phase analysis, the morphotropic domain structures and phase transitions, and the dielectric properties of the grown PZNT crystals were characterized by X-ray powder diffraction, polarized light microscopy and dielectric spectroscopy.

Ferroelectric domain structure characterized by prefractals of the pentad cantor sets in KH2PO4

Abstract Ferroelectric 180[ddot] domain structure periodic along the domain wall normal is formed in pyramidal growth sectors less strained in KH2PO4 (KDP) crystal. Each half period of the domain patterns optically observed between parallel polarizers is characterized by the first four prefractals of the pentad Cantor sets. It has been found that the averaged half period of these prefractal domain patterns is proportional to the square root of the thickness of the c plate. This verifies that the electrostatic energy originating from the depolarization field, as well as the wall energy, plays an important role in the prefractal domain formation. The prefractal domain patterns have been reproduced in the secondary electron images of a SEM. This verifies that the depolarization field also plays an important role in the secondary electron image formation. It is predicted, from the standpoint of the equilibrium internal energy, that a derivative of the 3rd prefractal domain pattern will correspond to one of ul...

Uniaxial birefringence in “cubic” Pb(Fe0.5Ta0.5)O3: Is there a hidden symmetry breaking?

Abstract The room temperature phase of the B-site disordered perovskite Pb(Fe0.5Ta0.5)O3 (PFT) has been studied by single crystal X-ray diffraction and by polarized light microscopy. While pyramidal (100) growth sectors display a weak birefringence, indicating a tetragonal symmetry with an optically uniaxial positive indicatrix, the structure of PFT crystals can be well refined in cubic space group Pm3m, however, the introduction of disorder on the A site is necessary. In the light of the optical symmetry, the (x100) A-site disordered cubic structure was considered as a mean structure averaged over tetragonal “domains,” each one containing Pb displaced just towards one of the three [100]cuh equivalent directions. Attempts at refinements in tetragonal symmetry and at mechanical (ferroelastic) switching of domains will be discussed.