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The effect of nonelectrolyte additives with hydrophilic and hydrophobic hydration on the growth of potassium dihydrogen phosphate (KH2PO) crystals in the kinetic mode at solution saturation temperatures of 323 and 303 K and a relative supersaturation of 0.025 has been experimentally investigated. The additives are found to affect differently, depending on their shape, concentration, and face index. It is revealed that the growth rate of {101} faces increases in the presence of additives with hydrophilic hydration of molecules and decreases in the case of hydrophobic additives. A model is proposed to explain the difference in the influence of the additives studied on the crystal growth. The influence is determined by the changes in the water structure in the surface layer of the crystallization solution; this conclusion must be taken into account when growing crystals from aqueous solutions in the presence of nonelectrolyte additives. [ABSTRACT FROM AUTHOR]

The influence of impurities of chlorides and nitrates of divalent Ca and Ba cations on the kinetic growth of potassium dihydrophosphate KHPO crystals at a saturation temperature of 323 K and relative supersaturation of 0.03 has been investigated experimentally. It is established that the impurity acts differently, depending on the face index, the impurity concentration, cation hydration, and the stability of the complexes formed in the solution by impurity salt ions. A model is proposed to explain the different influence of impurity ions on the growth of crystal faces. This influence is determined by the different hydration of cations and enhanced association of cations and anions of impurity salts in the surface layer with a lower dielectric constant. [ABSTRACT FROM AUTHOR]

The dielectric properties of potassium dihydrophosphate single crystals, which were grown from crystallization solutions at different pH, have been studied. The dielectric response of the single crystals is shown to vary substantially depending on the growth conditions and can be significantly different for samples from different growth sectors of the same single crystals and even within one sector. The results of this study are useful for optimizing the growth conditions of these single crystals. [ABSTRACT FROM AUTHOR]

Conductivity of potassium dihydrophosphate (KDP) crystals grown from solutions with different pH has been studied with due regard for the sectorial structure and the impurity composition of the crystals grown. The dependence of the conductivity parameters on these two factors is established. The data obtained lead to a conclusion on the formation of the real structure important for various electro-optical applications of KDP crystals and provide the optimization of growth conditions. [ABSTRACT FROM AUTHOR]

It has been established that metal impurities M[sup 3+] (Fe[sup 3+], Cr[sup 3+]) and M[sup 2+] (Co[sub 2+], Ni[sup 2+]) have a different effect on the kinetics of face growth of potassium dihydrophosphate (KDP) and potassium acid phthalate (KAP) crystals, which can hardly be interpreted in terms of the existing concepts. The crystallochemical analysis and computer modeling of the KDP structure provided the establishment of different mechanisms of incorporation of M[sup 2+] and M[sup 3+] impurities into the crystal structure: the first impurities form impurity clusters, whereas the second impurities occupy isolated positions. This fact predetermines the different deformation of the crystal matrix caused by M[sup 2+] and M[sup 3+] ions. The allowance for this fact provided the interpretation of different distribution coefficients of M[sup 2+] and M[sup 3+] impurities and their specific effect on the growth kinetics and defect concentration in KDP and KAP crystals. [ABSTRACT FROM AUTHOR]

The effect of benzene, acetone, acetic, formic, and oxalic acids, iron, and chromium on the growth kinetics of KH[sub 2]PO[sub 4] and C[sub 8]H[sub 5]O[sub 4]K crystal faces has been studied. It is found that low concentrations of organic impurities increase growth rates of some crystal faces (the so-called catalytic effect of impurity). This effect is rather weak in the case of organic acids, however, it is clearly seen in the presence of inorganic impurity (Fe[sup 3+]). The analysis of two models of growth (dislocation-free and B + S) under the assumption that the main cause of the catalytic effect is a decrease in the step energy showed that the calculated and experimental data are consistent only under certain assumptions that should be additionally verified both theoretically and experimentally. [ABSTRACT FROM AUTHOR]