Hardness and Etching Study of Amino Acid Doped KDP Crystals

Potassium dihydrogen phosphate (KDP) is a well-known nonlinear optical material. Vickers micro-hardness studies were performed to understand the mechanical behaviour of pure and amino acid doped KDP crystals. Indentations were made on smooth (100) plane of pure and amino acid doped crystals for different loads. The Vickers micro-hardness decreased as doping level of amino acid was increased, indicating that the KDP crystals became softer after doping. The indentation size effect, Kick's law and PSR model were verified for pure and amino acid doped crystals. Hays and Kendall's law analysis was also applied to the hardness data. The (100) face of pure and amino acid doped KDP crystals were selected for the chemical etching studies. The etchant used for all crystals were glacial acetic acid. The etching temperature was varied from 25 oC to 40 oC with increment of 5 oC. The etch pits was measured and Arrhenius law applied. The values of kinetic and thermodynamic parameters ware evaluated from width of etch pit.