Showing papers by "Toshio Kamiya published in 1994"
TL;DR: In this paper, a model of diffuse phase transition and relaxor ferroelectrics is proposed to explain dielectric properties of lead magnesium niobate (PMN) and strontium barium niobates (SBNT).
Abstract: Dielectric properties of lead magnesium niobate (PMN) and Ta-bearing strontium barium niobate (SBNT) were measured as a function of temperature, and the crystal structure of PMN was refined by the Rietveld analysis method The results of structure refinement indicate that the volume of polar microregions (PMR) increases with decreasing temperature The dielectric properties of PMN and SBNT are well explained by an advanced theory of dielectric dispersion The anomalous behavior in dielectric permittivity (e) observed on the low temperature side of T m, the temperature of e maximum, is explained by simple dielectric relaxation, while on the high-temperature side of T m is explained by the volume increase of PMR It is concluded that these is no phase transition around T m, and the diffuse phase transition is an overlapping phenomenon of volume increase of PMR, freezing process of fluctuating dipoles in PMR and dielectric dispersion around the measuring frequrncy A model of diffuse phase transition and relaxor ferroelectrics is proposed The difference between normal ferroelectrics and relaxor ferroelectrics is discussed from the viewpoints of spreading of soft-mode phonons and disorder in the crystals
94 citations
TL;DR: In this paper, bismuth silicate films were grown on a Si substrate by metalorganic chemical vapor deposition, and the capacitance of the specimen has increased fivefold over that of the original specimen.
Abstract: Crystalline bismuth silicate films were grown on a Si substrate by metalorganic chemical vapor deposition. A 100 nm SiO2 layer on Si was changed to bismuth silicate film by the reaction with a Bi and O2 gas mixture. A deposition of less than 30 min formed a single‐crystalline phase, having a certain crystallographic relation with (100)Si substrate. The capacitance of the specimen has increased fivefold over that of the original specimen. The crystallinity of deposited films was increased markedly by heat treatment. At the same time, the capacitance of the specimen increased. However, the oxidation of the Si substrate and the formation of a Bi‐rich surface caused a drastic decrease in the capacitance of the specimen.
18 citations
TL;DR: In this article, the electronic structures of perovskite-type oxides were calculated using the discrete variational X α method, and the calculated band structures agreed well with the previous reports and the DOS explained the XPS spectra measured well.
Abstract: Electronic structures of perovskite-type oxides were calculated using the discrete variational X α method. First, band structures and densities of states (DOS) were calculated for SrTiO3 and tetragonal BaTiO3. The calculated band structures agreed well with the previous reports and the DOS explained the XPS spectra measured well. Furthermore, band structures of SrTiO3/SrZrO3 superlattices with double period of SrTiO3 along [001], [011] and [111] directions were calculated. As a result, it was confirmed that the SrTiO3 and the [001] superlattice showed an indirect transition between the conduction band at the Γ point and valence band at the M or R point, while the [011] or the [111] superlattice showed a direct transition at the Γ point.
3 citations