![(a) Metastable zone of DKDP solutions (X=98%). (1) Monoclinic phase solubility; (2) Tetragonal phase solubility; (3) Metastable boundary in the presence of a growing crystal; (4) Metastable boundary without crystals, The region of tetragonal crystals growth is shaded. For comparison the data of Ref. [60] are shown (dotted line). (b) Monoclinic DKDP crystal (X--98%) grown by rapid growth technique at R z = 16 mrn/day. Crystal height is 13 cm.](https://www.researchgate.net/profile/Natalia-Zaitseva-5/publication/238119403/figure/fig2/AS:896245040160768@1590692877321/a-Metastable-zone-of-DKDP-solutions-X98-1-Monoclinic-phase-solubility-2_Q320.jpg)
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Rapid growth of KDP-type crystals
Abstract and Figures
Growth of KDP-type crystals on the point seed made possible to accelerate growth rates from traditional 1 mm/day up to 50 mm/day. This acceleration gave base to a development of the rapid growth technique for production of single crystals with the linear sizes up to 90 cm to obtain plates for laser radiation conversion in world-largest lasers. Scientific bases and technological principles of the method are considered in this review.
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... The production of increasingly high-quality crystals is important for a variety of scientific and technological fields. The demand includes solar cells [1,2], photosensors [3], photonic devices [4,5], infrared optics [6], radiation sensors [7], lasers [8], batteries [9,10], magnetic recording devices [11] and substrates for growing thin films [12]. ...
Scientific progress in the relevant fields of science and technology requires the production of crystals with quality beyond the current state of the art. Electro-magnetic levitation (EML) is a prospective method for the growth of high purity crystals, allowing to avoid any contact of the crystal melt with the crucible. Contactless crystal growth reduces the number of crystal defects commonly abundant in conventional crystal growth methods. The EML method also allows crystal growth of materials with very high melting points.
In this article, we report detailed measurements of the EML method. The induction coil used in this study has three turns and one counterturn. We subject different metal material (Al, Cu, Sn, and Ni) samples to the electromagnetic (EM) field induced by the induction coil. For each sample, we measure the induced lift force, Joule heating, and components of magnetic induction as a function of position inside the coil. The results show that the maximum heating in an EML coil is emitted in the area below the levitation zone, a discrepancy not reported earlier. Our findings suggest that this shift should be considered in coil design to avoid instability of the levitated material.
We hope that this study will serve as a steppingstone for the development of EML techniques. The experimental results we provide will be used to evaluate the accuracy of current and future theoretical models of EML coils. This, in turn, will facilitate progress in the application of EML to the growth of larger crystals of higher quality.
As a new generation of photoelectric materials, organic–inorganic halide perovskites have been widely used in photodetectors, solar cells and other fields, but most of the current mainstream applications are thin film materials.
Nonlinear‐optical (NLO) crystals require birefringent phase matching (BPM), particularly in the solar‐blind ultraviolet (UV) (200–280 nm) and deep‐UV (100–200 nm) regions. Achieving BPM requires optimization of optical dispersion along with having large birefringence. This requirement is especially critical for structures with low optical anisotropy, including classical phosphate UV–NLO crystals like KH2PO4 (KDP). However, there is a scarcity of in‐depth theoretical analysis and general design strategies based on structural chemistry to optimize dispersion. This study presents findings from a simplified dielectric model that uncover two vital factors to micro‐optimize transparent optical dispersion: effective mass (m*) of excited states and effective number (N*) of photo‐responsive states. Smoothing of dispersion occurs as m* increases and N* decreases. First‐principles analysis of deep‐UV KBe2BO3F2‐family structures is used to confirm the conciseness and validity of the model. It further proposes substituting K⁺ with Be²⁺ to decrease N* and increase m* while enlarging bandgap. This will lead to improved dispersion and an overall enhancement of KDP's BPM capability. The existing BeH3PO5 (BDP) is predicted to improve the shortest BPM wavelength for second‐harmonic generation, from 251 nm in KDP to 201 nm in BDP. BDP's extension into the broader UV solar‐blind waveband fully supports the proposed optimization strategy.
Dans le cas d'un cristal qui croît dans des conditions de convection, les caractéristiques de son entourage peuvent induire une anisotropie dans l'apport de matière sur des faces homologues. Cette situation se produit lorsque les faces ont des orientations différentes par rapport aux lignes de flux.
On vérifie expérimentalement cette hypothèse. On a utilisé un appareil de croissance cristalline en solution par convection artificielle. On obtient des données sur les vitesses de croissance de cristaux d'ADP et de KDP. Simultanément, au moyen d'un système qui permet d'observer les lignes de flux, on fait une étude hydrodynamique. En combinant les deux types de données, on élabore un modèle qui tient compte de l'influence de l'hydrodynamique sur la morphologie cristalline.
The repulsion or capture of foreign particles encountered by a growing crystal has two aspects: firstly, die pressure the crystal may exert on the body, and secondly, the supply of material to areas in contact with such body.
KDP (KH2PO4) single crystals up to 47 cm in size have been grown by the rapid growth technique on the point seed in glass crystallizers of 1000 L in volume at growth rates of 10 to 25 mm/day in both the [001] and [100] directions. Measurement of the optical quality of 41 X 41 cm single crystal plates are presented.
The kinetics of crystallization from solution have traditionally been correlated with solution supersaturation evaluated in terms of solution concentration. In this paper the consequences of using activities rather than concentrations to determine the driving force for the crystallization process are examined. Using experimental kinetics for the crystallization of K2SO4 and KH2PO4 from aqueous solution as examples, best values of the parameters appearing in crystal growth correlating equations evaluated using both activities and concentrations as a measure of driving force are compared. For these two systems the differences between the two cases are comparatively small, being of the same order as the uncertainty in the parameters which usually arises from experimental error and curve fitting procedures. Values of the interfacial energy calculated both from the growth kinetics using activities as a measure of driving force and from the physical properties of the system are in good agreement. A comparison of the use of activities and concentrations to determine the influence of crystal size on solubility using the Gibbs-Thomson equation is also made.
Comparative analysis of main optical characteristics of KDP crystals grown by traditional technique at growth rates up to 1 mm/day and by rapid growth technique at growth rates ranging from 15 to 40 mm/day is carried out. The results on anomalous biaxiality absorption ard scattering of light effective nonlinear susceptibility and bulk laser damage threshold of crystals are given. It is shown that the increase of the crystal growth rate by more than one order does not deteriorate the crystal optical quality.
A special kind of liquid inclusions named “hairs” are described in the present work. These inclusions were observed in the crystals grown from a point seed at rates of 10–30 mm per day in the [001] direction. It was shown that formation of “hair” inclusions cannot be described by known mechanisms. Their occurrence is not connected with the dislocation structure but probably induced by the morphological conditions on growing surface at high growth velocities.