Large-particle (15 and 40 µm) Co-MCM-41 was synthesized using a pseudomorphic transformation. To maintain the spherical shape of the parent silica particles, overcondensation of silanol groups has to be avoided under a moderately basic synthesis condition. After 4 days of autoclaving at 100°C with the Co-MCM-41 synthesis solution of which the initial pH was adjusted to 12.0, nonruptured spherical Co-MCM-41 particles, having one-dimensional pores in which Co ions are highly dispersed, were successfully synthesized. The reduction stability of this catalyst was affected by Co ion location controlled by pH adjustment and hydrogen spillover from residual cobalt oxide on the surface, which had not been incorporated into the silica matrix.

No abstract

No abstract

Ba(Fe 1/3 Nb 2/3 )O 3 has been prepared by well established ceramic technique at 1100 • C. It exists in disordered cubic phase with tetragonal superlattice structure. It exhibits single relaxation frequency at 533 KHz. The relaxation spectra imply the presence of interfacial polarization. The dielectric constant and relative loss have been determined as a function of temperature. It shows a diffused phase transition at 440 K. The measurements of Schottky barrier, bandgap and resistivity have also been carried out. On the basis of the observations the presence of dielectric microdomains is interpreted. The, observations are compared with Ba(Fe 1/2 Nb 1/2 )O 3 .