Papers by Author: Rei Fujiwara

Abstract: Barium titanate (BTO) inverse opal photonic crystals were fabricated by a process of self-assembly of polystyrene opal template in combination with electrophoretic deposition (EPD) of nanoparticles from BTO suspension. In this process, stable monodispersed suspension of BTO nanoparticles was prepared by dispersing BTO gel into a mixed solvent of 2-methoxyethanol and acethylacetone. Then the BTO nanoparticles were infilled into the interstices of the opal template formed by monodisperse polystyrene microspheres by electrophoretic deposition, and then polystyrene template was removed by calcining the specimen at a final temperature of 500oC. SEM images show that the inverse opals possess face-centered cubic (fcc) structure with center to center distant of the air spheres 310 nm. A photonic bandgap in the visible range is observed from reflection spectra of the sample. Such BTO inverse opals as photonic crystals should be useful in device applications.

Abstract: Nanosized Y2O3:Eu3+ crystalline powders with average particle sizes around 100 nm, measured by field-emission scanning electron microscopy (FE-SEM), have been synthesized by a polymerized precursor method using carboxymethyl cellulose (CMC). The nanocrystalline phosphors exhibit intense photoluminescence (PL) and cathodoluminescence (CL) around 612 nm, being attributed to the 5D0-7F2 transition of Eu3+. Electroluminescence (EL) properties of the nanophosphors in the form of thick films were investigated, and emission of red light with maximum intensity at 612 nm (corresponding to x = 0.57 and y = 0.32 in the CIE chromaticity diagram) was observed under high ac field at 1 kHz. The obtained results suggest a possibility that Y2O3:Eu3+ nanopowders can be used as a red-emitting phosphor for EL devices.