Author/Authors :
Kopnin، نويسنده , , E.M. and Istomin، نويسنده , , S.Ya. and Dʹyachenko، نويسنده , , O.G. and Antipov، نويسنده , , E.V. and Bordet، نويسنده , , P. and Capponi، نويسنده , , J.J. and Chaillout، نويسنده , , C. and Marezio، نويسنده , , M. and de Brion، نويسنده , , S. and Souletie، نويسنده , , B.، نويسنده ,
Abstract :
The K1 − xBaxNbO3 (0.2≤x≤0.5), BaNbO3 and k0.5Sr0.5NbO3 compounds have been synthesized by high-pressure high-temperature technique in a Belt-type apparatus. The synthesis of the K-containing phases carried out in evacuated sealed silica tubes led to the preparation of polyphasic samples. The phases obtained have an ideal perovskite-like structure. The a parameter of Ba-containing compounds increases concomitantly with increasing Ba concentration. Studies of the K-containing phases by X-ray powder diffraction did not reveal any distortion from cubic symmetry. Electron Dispersive Spectroscopy (EDS)-analysis confirmed the cation nominal stoichiometry. Resistivity measurements showed semiconducting-like type of conductivity for the K1 − xBaxNbO3 (0.2≤x≤0.5) and k0.5Sr0.5NbO3 samples, but the relative increase of ϱ with the decrease of temperature became smaller for the phases with lower Nb valence, and moreover K0.5Sr0.5NbO3 exhibited a slight decrease of the resistivity in the 100-4.2 K temperature range. On the contrary, BaNbO3 after high-pressure treatment showed a metallic-like behaviour down to 4.2 K.
