Can we visualise static electricity, which everyone in the world knows about? Since static electricity is generated by contact or peeling, it may be a source of malfunction of electronic components, whose importance is steadily increasing, and even cause explosion and fire. As static electricity is invisible, makeshift measures of static electricity are taken on various surfaces; there is also a common view that it is hard to take effective measures. Here we present a specific luminescent material, SrAl₂O₄: Eu²⁺, which emits light at excitation by an electrostatic charge in the air. Till now, in the interaction between electricity and luminescent materials, it was considered that emission of light is enabled by accelerated particles colliding with the luminescent materialin vacuo. There have been no reports on luminescent materials being responsive to low-energy electrostatic charges under atmospheric pressure. Using SrAl₂O₄: Eu²⁺luminescent material discovered by us, we succeeded for the first time in static electricity visualisation in the form of green light. In addition to the fact that such static electricity induced luminescence assists in solving electrostatic-related problems in the industry, it also provides a new measurement method that facilitates the observation of previously invisible electric charges in the air.

A mixture of positive and negative static charges exists in the same plane on an insulator surface, and this can cause production quality problems at manufacturing sites. This study developed a system with a vibration array sensor to rapidly measure the surface potential distribution of an object in a non-contact and non-destructive manner and with a high spatial resolution of 1 mm. The measurement accuracy differed greatly depending on the scanning speed of the array sensor, and an optimum scanning speed of 10 mm/s enabled rapid measurements (within <3 s) of the surface potential distribution of a charged insulator (area of 30 mm × 30 mm) with an accuracy of 15%. The relationship between charge and dust on the surface was clarified to easily visualize the uneven static charges present on it and thereby eliminate static electricity.

Ba-Cu-O films have been grown by pulsed laser deposition. Investigation of their transport properties and characterization of electronic structure by in-situ photoemission spectroscopy have been carried out. The films grown at 450 ~ 480 °C from BaCuO₂ target had simple infinite layer structure with lattice parameter of a and c about 0.385 and 0.405 nm, respectively. Conductivity of these films were, however, poor. Usage of BaCu_0.75O_x target and addition of CO₂ into the growth atmosphere resulted in an expansion of c-axis length up to 0.810 ~ 0.835 nm and a significant rise of conductivity. This structure is represented as ''2c''. For the 2c phase, conductivity above of 10³ S/cm was achieved by adjusting their growth temperature in the range of 500 ~ 530 °C. Most of the highly conductive 2c phase showed superconductivity. The maximum temperature of onset of the superconducting transition and zero resistance state obtained so far were 60 and 47 K, respectively. Finite spectral weights at Fermi level were successfully observed in in-situ photoemission spectra of the 2c phase. In valence band region, a prominent peak with u 3d character located at a binding energy around 1.6 eV. Though this low binding energy suggested a rather high hole concentration of mobile holes were around middle of 10²¹ cm⁻³ range. These results about electronic structure indicate a coexistence of conventional CuO₂ planes and distorted ones. The latter structure might play charge-reserving blocks, though some portions of holes should localize in them. Correlations between the properties and electronic structure are to be discussed.

We report the superconducting properties of (Cu, C)Ba₂CuO_y thin films deposited by RF magnetron sputtering from targets with a nominal composition of Ba₂Cu_1.5O_y. The thin films were grown in mixed Ar (5~40 mTorr), O₂ (0~1.2 mTorr) and CO₂ (0~1.8 mTorr) atmosphere. The epitaxial c-axis oriented thin films with c-axis length in the range between 7.96 Å and 8.82 Å were obtained on SrTiO₃(100) substrates, but superconductivity was observed only for the films which have the c-axis length with 8.01 Å and 8.32 Å. By optimizing deposition conditions, the excellent (Cu, C)Ba₂CuO_y thin film with T_c = 62K and superconducting transition width ΔT_c = 1.5 K was successfully obtained.