The kinetics of domain nucleation during polarization reversal in uniaxial ferroelectric lead germanate has been studied in detail using optical methods of visualization of the instantaneous domain configurations. Transient and steady-state regimes of nucleation have been discovered. The contribution of transient nucleation to polarization reversal essentially increases as the field is increased. Attention is drawn to the similarity between ferroelectric switching and a first-order phase transition. The obtained results can be used for the improvement of the description of switching behaviour in high fields.
Thin films of the ‘electron-doped’ superconductor (Nd,Ce)2CuO4 (NCCO) have successfully been prepared by post-oxidation of double-layer films of Nd(Ce) and Cu metals, previously deposited onto the (001) surface of SrTiO3 (STO) by DC magnetron-sputtering. The microstructure of a series of thin films after oxidation in air at 600-1100°C are examined by cross-sectional high-resolution transmission electron microscopy (HRTEM). The formation of NCCO crystallites is observed at the film/STO interface, when the oxidation temperature is higher than 700°C, but single-crystalline films are not obtained by an oxidation below 900°C. Single-crystalline NCCO films of good epitaxial relation with the STO substrate are, on the other hand, obtained by post-oxidation between 900 and 1000°C, and superconductivity at Tc=14 K is achieved by additional annealing at 400°C in vacuum. The NCCO films obtained by post-oxidation above 1000°C, however, tend to contain many planar faults, and also thin layers with unknown structures are often formed at the NCCO/STO interface.
Recent considerations on climatic variations are reviewed and following points are summarized, (1) Distribution, influences on human society and causes of climatic variations is dependents of time scale of climatic variation. (2) Climatic system is composed of various elements and climatic status determined by delicate balance of these elements. (3) Increase of human consumption of fossil fuel brings increase of CO2 in the atmosphere. If such trends continues, marked change of climate will occur on the middle of next centuries.
