Papers by Keyword: KTaO₃

Abstract: The perovskite oxides property are wide band-gap semiconductors and are sensitive to visible light but opaque. In this paper, we are interested in the resistance change of insulating KTaO₃ crystals could decrease as much as 3-4 orders of magnitudes under exposure to focused sunlight. But, these resistances under ambient pressure changed back quickly after light was off. And the resistance changed in a similar way under exposure to synchrotron light but the increase resistance rate was much slower under vacuum condition. However, the large increase resistance rate by increasing the oxygen pressure. From the ARPES study, the change in resistance occurred due to the oxygen vacancy induced by the exposure to ultraviolet light. These oxygen vacancies induce two-dimensional electron gas at the surface KTaO₃. This indicates that the KTaO₃ could be used as a light sensing device.

Abstract: The Bi0.2K0.8(Zn0.1Ti0.1)Ta0.8O3 and Li doped ceramics prepared via the solid-state reaction technique were investigated. The XRD patterns show the single phase cubic perovskite structure without any evidence of secondary phases when sintered at 1250 oC for undoped Bi0.2K0.8(Zn0.1Ti0.1)Ta0.8O3 and sintered at 1100 oC for Li doped one. The dielectric properties indicate the diffused phase transition (DPT). The dielectric loss of undoped ceramic increases with increasing frequency in temperature range 270 oC down to -150 oC, which suggests low temperature relaxation, while the dielectric loss of Li doped ceramic reveals the interesting lower value over a wide temperature range of about 0 - 300 oC.

Abstract: Effects of mixing dye sensitizer for the photocatalytic activity of dye-sensitized Pt/K0.95Ta0.92Zr0.08O3 was investigated. It was found that the photocatalytic activity was greatly improved by mixing dye sensitizer on the catalyst, and among the examined combination of organic dyes, the highest photocatalytic activity was obtained by mixing Cr-tetraphenylporphyrin (Cr-TPP) and Pentametylene bis[4-(10, 15, 20-triphenylporphine-5-yl)benzoate] dizinc(ΙΙ) (Zn-TPP dimer). In order to identify the effect of dye sensitizer, photovoltaic behavior of the dye-sensitized KTaO3 was investigated. The lifetime of the photo-exited electron and hole can be improved by coating with dye sensitizer. Thus, the effect of porphyrinoids would be explained by the improved efficiency of charge separation.