Stoichiometric Ca2CuO3, having square-planar Cu-chains [C. L. Teske and H. Müller-Buschbaum, Z. Anorg. Allg. Chem. 379, 234 (1970); M. Hjorth and J. Hyldtoft, Acta Chem. Scand. 44, 516 (1990)], is expectedly antiferromagnetic due to 1D intrachain superexchange [K. Okuda, S. Noguchi, K. Konishi, H. Deguchi, and K. Takeda, J. Magn. Magn. Mater. 104–107, 817 (1992)]. Nonetheless, we report remarkable spontaneous ferromagnetism at 293 K after sintering, prominently in oxygen. This apparently introduced excess oxygen at vacant quasioctahedral sites, promoting spin-flip and ferromagnetic interchain coupling. Thermogravimetry (TGA) revealed excess oxygen, ≈0.17 O/Cu. X-ray diffraction (XRD) yielded a comparatively smaller unit cell. Ferromagnetism disappeared by oxygen depletion, mimicking reported nonmagnetism of Ca2CuO3−δ [Okuda et al. (1992)]. Elemental analysis showed insignificant magnetic impurity traces. Tc ranged between 680 K and 723 K, depending on freshness and purity. Saturation magnetization varied with processing, optimally 0.30 A · m2/kg at 1.0 T applied field. Coercivity and remanence varied with purity.

Nanocrystalline Si particles of 10 nm size, doped with traces (1 at. %) of Sn, are prepared by mechanical attrition in an inert ambient. After stain-etching, the particles photoluminesce at room temperature. 119Sn Mössbauer spectroscopy, Raman scattering, photoluminesce, and Fourier transform infrared spectroscopy measurements performed as a function of stain-etching time reveal systematic changes, and suggest that the molecular structure of porous Si consists of nanocrystalline Si particles with surfaces passivated by H and/or O atoms.

Eine tetragonale Phase SrCuO2 bewirkt möglicherweise das supraleitende Verhalten von im Sol‐Gel‐Verfahren hergestellten Proben der nominalen Zusammensetzung Bi2Sr2CuO6. Die Meßergebnisse weisen auf eine Sprungtemperatur bis 70°C hin, wobei die Supraleitung auf eine zu weniger als 0.1% in der Probe vorhandene Phase zurückzuführen ist. Acht Proben zeigten Anzeichen von Raumtemperatursupraleitung, bei vierzehn weiteren lagen die Tc‐Werte zwischen 25 und 110 K.

A tetragonal phase SrCuO 2 possibly causes the superconducting behavior of the samples with the nominal composition Bi 2 Sr 2 CuO 6 prepared in the sol‐gel process. The results of the measurements indicate a critical temperature of 70 °C, and the superconductivity is attributed to a phase present in the sample in less than 0.1%. Eight samples show evidence of room‐temperature superconductivity, and an additional fourteen samples show superconductivity between 25 and 110 K.

A ferromagnetic series of alkaline earth cuprates has been synthesized utilizing sintering temperatures lower than those normally used. Curie point determinations for these compounds have been established and range from room temperature to 700°C.