The concentration effects of s-, p-, d- and f-block element doping on the growth, crystalline perfection and properties of KDP crystals

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The effect of dopants (over a wide concentration range from 0.5 to 10 mol%), namely s-, p-, d- and f-block elements (Mg, Sb, Pd and La) on the growth process, crystalline perfection, external morphology, vibrational patterns, XRD profile and second order nonlinear optical (NLO) properties of potassium dihydrogen phosphate (KH2PO4, KDP) crystals grown by the slow evaporation solution growth technique has been systematically investigated. Incorporation of the dopants into the crystalline matrix even at low concentrations was well confirmed by the inductively coupled plasma (ICP) technique. The change in intensity patterns in XRD profiles of doping specimens reveals lattice distortion, further supported by slight shifts in characteristic vibrational frequencies in FT-IR. The scanning electron microscope (SEM) micrographs exhibit the effectiveness of the impurity in varying the surface morphology. The high-resolution X-ray diffraction (HRXRD) studies used to evaluate the crystalline perfection reveal many interesting features on the ability of accommodating the dopants by the crystalline matrix. It appears that the crystalline perfection depends mostly on the concentration of the dopant. Multi-peaks appear for highly doped specimens indicating the inhomogeneous accommodation. The second harmonic generation (SHG) efficiency is enhanced considerably when the concentration of the dopant is low while depressed activity is observed with poor crystalline perfection at high concentrations irrespective of the nature of the dopants.