Structural, FTIR and Dielectric Study of Lithium Doped KDP Crystals

Potassium Dihydrogen Phosphate (KDP) crystals are well known for nonlinear optical (NLO) properties and find different optical applications. In the present study, various amount of lithium doped KDP single crystals were grown by slow solvent evaporation method. For doping lithium chloride was mixed with KDP solution in 1, 3 and 5 weight percent. The grown crystals were transparent and prismatic in nature with maximum dimension of 5 cm × 1.5 cm × 0.5 cm. The presence of lithium was detected by flame test. The powder XRD study indicated single phase nature of the grown crystals and the doping caused minor change in the KDP structure, which was confirmed by the minor change in unit cell parameters. From FTIR study the functional groups like O-H, P-O, P-OH were identified but no major change due to lithium doping was found. The dielectric study was carried out in the range from 10 kHz to 10MHz indicated sharp decrease in dielectric constant with frequency of applied field after 70 kHz. The AC conductivity increased with increase of frequency. The dielectric constant was found to be sensitive to doping in KDP.