Influence of potassium chloride doping on the properties of potassium dihydrogen phosphate crystal for nonlinear optical applications

Nonlinear optical single crystals of pure potassium dihydrogen phosphate and potassium chloride-doped potassium dihydrogen phosphate were grown by slow evaporation technique at room temperature. The powder X-ray diffraction analysis shows the reflection lines of the doped KDP crystal correlate well with the observed individual parent compound pure KDP with a slight shift in the intensity of the diffracted peaks. The crystal structure lattice parameters and space group was determined by single-crystal XRD studies. The existences of several functional groups were extricated by shifting of peaks in FTIR spectral inspections. The UV cut-off wavelength is found to be 381 nm for pure KDP 383 nm for potassium chloride-doped KDP crystals, respectively, using UV–Vis-NIR studies. The permittivity and dielectric loss tangent of the grown crystals are less at elevated frequencies with different temperatures. The correlative second harmonic (SHG) potency was evaluated by the Kurtz and Perry method for the doped crystal, and it was found to be 0.34 times higher than that of the pure KDP. The thermal stability measurement was carried out by TG/DTA study. Mechanical stability was found from load-dependent Vickers micro-hardness analysis.