Growth and Characterization of KI-Doped KDP Single Crystals

Crystalline materials are solids in which atoms, molecules, or ions are arranged in a regular and repeating three-dimensional structure. Potassium dihydrogen phosphate (KDP) is an important crystalline material because of its optical, ferroelectric, and piezoelectric characteristics. In the present study, the influence of potassium iodide (KI) incorporation on the properties of potassium dihydrogen phosphate (KDP) single crystals was investigated. Both undoped KDP and KI-doped KDP crystals containing 0.10 mole%, 0.15 mole%, and 0.20 mole% KI were prepared by the slow evaporation solution-growth method. The optical behavior was examined by UV-Visible spectroscopy over the wavelength interval of 200-1100 nm, while Fourier transform infrared (FTIR) spectroscopy was used to examine the characteristic functional groups and bonding environment. Thermogravimetric analysis (TGA) was also conducted to investigate the thermal behavior of the crystals. The obtained crystals were transparent and stable. The UV-Visible measurements showed a clear change in the transmission and absorption characteristics after KI incorporation, while the lower wavelength cut-off remained close to 400 nm for the investigated samples. The TGA profiles showed multi-stage thermal decomposition. The first major decomposition region was observed at 195.59°C for pure KDP, 221.09°C for 0.10 mole% KI-doped KDP, and 202.48°C for 0.20 mole% KI-doped KDP. These observations indicate that KI incorporation modifies the optical and thermal behavior of KDP single crystals.