Electroceramics in Japan XIII

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Authors: Shingo Fujihara, Yuichiro Kuroki, Tomoichiro Okamoto, Masasuke Takata
Abstract: A ceramic rod of GdBa2Cu3O7-δ with Gd2BaCuO5 core was prepared using a dip coater and sintered at 950oC. A hot spot appeared when a certain voltage was applied to the rod. Oxygen sensing characteristics of the rod were investigated. It was found that the response time of the oxygen sensor using the rod with the core was shorter than that without the core, because the length of the oxygen diffusion in GdBa2Cu3O7-δ part in the rod with the core was shorter than that without the core.
Authors: Mamoru Ohashi, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato
Abstract: Photocatalysts for overall water splitting have great potential in solar energy applications. A variety of photocatalysts have shown activity for water splitting. In particular, oxysulfides are the great interest because of their ability to generate H2 and O2 from water under visible light. However, they are generally synthesized under H2S flow, which is an extremely harmful gas for humans. In this study, La2O2S2 was synthesized at low temperature without H2S gas, and its photocatalytic activity was confirmed by hydrogen generation experiments.
Authors: Kenichiro Iwasaki, Yoshihiro Takahashi, Hirokazu Masai, Takumi Fujiwara
Abstract: We examined photoluminescent (PL) and afterglow properties in bazirite (BaZrSi3O9) phases with Sr2+-, Sn4+-, Ge4+-, and Ti4+-impurities, in order to elucidate effect of the impurity-addition on these properties. The bazirite phases studied showed blue PL and afterglow regardless of sort of the impurities. Origin of PL and afterglow emission in the bazirite phase is also discussed.
Authors: Yoshihiro Takahashi, Hirokazu Masai, Takumi Fujiwara, Minoru Osada
Abstract: In-situ observation of inelastic light scattering of boson region in glassy Ba2TiGe2O8 (BTG) was performed during heating process. The in-situ boson observation revealed structural relaxation below glass-transition temperature in the as-quenched sample, suggesting the nanometric structural heterogeneity. Relation of the boson behavior to crystallization tendency is also discussed.
Authors: Itta Komiya, Keisuke Nakao, Kiyofumi Yamagiwa, Jun Kuwano
Abstract: The compositions La0.56Li0.33TiO2.95F0.05•xLiF (x=0-025) were prepared by addition of LiF to the disordered form of the well-known Li ion conductor La0.56Li0.33TiO3. Although the total conductivities improved, there was no change in the bulk conductivity with LiF addition. No reflections due to LiF were observed in their XRD patterns, and the profiles and the chemical shifts of their 19F MAS-NMR resonances were almost the same as those of LiF. The results indicate that no substitution of F takes place, and that the added LiF acts simply as a sintering assistant agent.
Authors: Ayano Toda, Kazuyoshi Uematu, Tadashi Ishigaki, Kenji Toda, Mineo Sato
Abstract: Ba2Gd3Li3Mo8O32:Eu3+ phosphor was prepared using a single mode microwave oven operated at a frequency of 2.45 GHz and a power of 500 W. The temperature of raw materials, mixtures of BaCO3, Gd2O3, Li2CO3, MoO3 and Eu2O3 subjected to microwave irradiation increased to about 1073 K in 120 s, followed by a sharp drop despite irradiating the raw materials continuously. By measuring the dielectric loss factor of the raw materials at 2.45 GHz, the temperature increased could be attributed to the fact that MoO3 absorbs a high proportion of microwave energy. In the case of the microwave heating method, the phosphor particles were highly non-aggregated.
Authors: Yuji Akiyama, Ai Fukumori, Masayuki Takada, Yuuki Sato, Shinzo Yoshikado
Abstract: The effects of the addition of Y or both Y and Zr to Bi-Mn-Co-Sb-Si-Cr-Ni-added ZnO varistors on the varistor voltage and the tolerance characteristics of electrical degradation were investigated. The deterioration of the tolerance characteristics of electrical degradation by the addition of Y was probably caused by an increase in the number of willemite (Zn2SiO4)-type particles or a decrease in the number of spinel (Zn2.33Sb0.67O4)-type particles, but this deterioration was reduced by adding Zr. Moreover, the reduction in the average ZnO grain size due to the addition of Y was a major factor in the increased varistor voltage, and the ZnO grain growth was inhibited by the formation of an un-known compound after adding Y. The varistor voltage of a varistor with 2 mol% added Y increased by approximately 50% compared to a varistor with no Y added.
Authors: Ai Fukumori, Masayuki Takada, Yuji Akiyama, Yuuki Sato, Shinzo Yoshikado
Abstract: With the goal of fabricating low-breakdown-voltage varistors, the effect of adding Ba to ZnO varistors on the ZnO grain size was investigated. Grain growth of ZnO could be markedly promoted by adding both Ba and Bi. The maximum grain size was approximately 150 μm and the minimum varistor voltage was approximately 12 V/mm. However, it had relatively poor tolerance characteristics for electrical degradation. It is speculated that when adding both Ba and Bi to a Mn–Co-added ZnO varistor, it is necessary to form the molten phases of Ba and Bi to promote grain growth of ZnO. It is also conjectured that the growth of ZnO grains is not promoted when Ba and Bi do not coexist in the molten phase because Ba forms compounds with Mn independently with the addition of small amounts of Bi.

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