Electron crystallographic image-processing investigation and superstructure determination for (Pb_0.5Sr_0.3Cu_0.2)Sr₂(Ca_0.6Sr_0.4)Cu₂O_y

An electron crystallographic image-processing technique based on the combination of high-resolution electron microscopy and electron diffraction has been developed to investigate the commensurate structural modulation in the high-T_c superconductor (Pb_0.5Sr_0.3Cu_0.2)Sr₂(Ca_0.6Sr_0.4)Cu₂O_y. In the determined projected potential map of resolution about 1.25 Å, the occupational and/or positional modulation has been clearly observed for all atoms, including oxygen.