La_2CuO_4-CuO複合体の表面組成と伝導度に与えるH_2S処理効果

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A composite material containing La_2CuO_4 and CuO was directly synthesized by thermal decomposition of a heteronuclear CuLa(dhbaen)(NO_3)・nH_2O complex, where dhbaen is N, N´-bis(3-hydroxysalicylidene)-ethylenediamine. The mean particle size was of the order of 200 nm for a sample decomposing at 800℃. The exposure to 7.8 ppm H_2S at 50℃ for 6 d (the exposure gas was alternately changed from air to 7.8 ppm H_2S at 6 h intervals for 6 d) resulted in the formation of copper sulfide and lanthanum surface on the surface. At 100℃, the surfaces were mostly covered with both sulfide and sulfate. Lanthanum sulfate and copper sulfide, without copper sulfate, were formed at temperatures below 200℃. Copper sulfate was detected when the sample was exposed at 250℃. For samples exposed at 100℃, the atomic ratio determined by X-ray photoelectron spectroscopy (XPS) for [S(sulfate)]/[La] was 1.6 on the surface and decreased to 0.01 with increasing depth of Ar sputtering on the surface. The ratio of [S(sulfide)]/[Cu] was 0.99 on the surface and decreased to about 0.45 upon Ar sputtering. However, [S(sulfate)]/[La] and [S(sulfide)]/[Cu] ratios on the surface were 0.03 and 0.39, respectively, for single-phase La_2CuO_4 prepared by the solid state reaction method after the exposure. It is concluded that the reactions of Cu and La in La_2CuO_4 with hydrogen sulfide are accelerated by the presence of well-dispersed CuO.
社団法人日本セラミックス協会の論文
2000-12-01

La_2CuO_4-CuO複合体の表面組成と伝導度に与えるH_2S処理効果

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