Mechanical Properties of Potassium Dihydrogen Phosphate Single Crystal by the Nanoindentation Technique

Mechanical properties of potassium dihydrogen phosphate single crystal (KH2PO4, KDP) at room temperature were investigated using nanoindentation approaches. This study was carried out for two crystallographic planes of KDP single crystal, (001) crystallographic plane and the tripler crystallographic plane. The hardness and the reduced modulus values were calculated by the most commonly used Oliver–Pharr method. It was found that hardness and reduced modulus exhibited significant peak load dependence. Furthermore, the strong anisotropy of the hardness and reduced modulus were observed on two tested surfaces. At the same time, the indentation anisotropy of hardness and reduced modulus on each crystallographic face along different directions were estimated in detail. The results showed that these two faces behave quite differently from each other. The variations of hardness and reduced modulus values for (001) face and the tripler face both were periodic due to the rotational symmetry of crystallographic fac...