|Budget Amount *help
¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1996 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1995 : ¥1,500,000 (Direct Cost : ¥1,500,000)
We made a morphological phase diagram as a function of agar concentration and a ratio of iodide ion and lead anion. In order to understand the crystallization process of lead iodide, we carried out in-situ experiments by which the propagation velocity of crystallization is measured. As a result, it was found that the propagation velocities both in the banding structure and the branching structure are the same, suggesting that the diffusivity difference due to concentration difference of agar does not cause the morphological transition. From the observation of formation process of branching structure, it is found that the heterogeneous nucleation on the surface of large crystals is deeply related to the formation of branching structure. From the observation by the scanning electron microscope (SEM), crystal number density in banding structure is different from that in branching structure by three orders of magnitude. In addition, from the SEM observation, agar structure difference depending on the agar concentration is found not to cause the number density difference. From a series of experiments, it is found that the lead iodide nucleation process is not simple, rather complex that not only the monomer concentration of lead iodide but also the excess anion and ion play important roles. As a result of these experiments, it is concluded that the subtle effect of agar concentration on the nucleation process causes the morphological transition between the banding structure and branching structure.