Papers by Author: Keisuke Kageyama

Abstract: The effect of the surface preparation in samarium doped semiconducting barium titanate [(Ba_1-xSm_x)TiO₃] ceramics with (Ba, Sm)/Ti ratio of 1.000 was studied by means of isotope tracer technique using a secondary ion mass spectrometer. The surfaces of specimens were prepared with the chemical mechanical polishing (CMP) with colloidal silica slurry or the mechanical polishing (MP) with diamond paste. The oxygen diffusion coefficients obtained in the CMP samples were small compared to those in the mechanical polished samples. This fact suggests that the surface prepared with CMP has less oxygen defect concentration. Moreover, it was also indicated that high temperature treatment over 1000 °C is required for annihilation of defects formed by MP. The oxygen diffusion study used CMP sample brings the useful information on the oxygen defect chemistry in Sm doped BaTiO₃.

Abstract: The electrooptic material of transparent (Sr,Ba)Nb2O6 (SBN) ceramics was prepared using the conventional solid-phase reaction process with no special techniques such as hot-pressing or hot isostatic pressing. The SBN ceramics were made transparent by substituting a small amount of Zn2+ ion for the B site (Nb5+ ion site). The Curie temperature was increased by substituting a small amount of Na+ ion for the A site (Sr2+ or Ba2+ site). Furthermore, the orientation of the SBN structure by the template grain growth (TGG) method improved the electrooptic properties of the ceramics.