Domains of KDP crystal act as a diffraction grating for light propagating along the c-axis of the crystal. Various static properties of domains are studied by making analysis of diffraction patterns and domain configurations.
Experiment was performed in the range of temperature between 95˚K and $T_c$. Domain widths is measured to be in the order of $10^{-4}$ cm and widths of positive and negative domains are found to be slightly different from each other.
Domain wall energy is estimated to be 0.05 - 7ergs/$cm^2$, and also judging from the observation of the process of domain formation, KDP crystal seems to undergo the 1st order phase transition.
