Synthesis, structure, and resistivity properties of K 1 − xBa xNbO 3 (0.2 ≤ x ≤ 0.5) and K 0.5Sr 0.5NbO 3

Abstract

The K 1 − xBa xNbO 3 (0.2≤x≤0.5), BaNbO 3 and k 0.5Sr 0.5NbO 3 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 K 1 − xBa xNbO 3 (0.2≤x≤0.5) and k 0.5Sr 0.5NbO 3 samples, but the relative increase of ϱ with the decrease of temperature became smaller for the phases with lower Nb valence, and moreover K 0.5Sr 0.5NbO 3 exhibited a slight decrease of the resistivity in the 100-4.2 K temperature range. On the contrary, BaNbO 3 after high-pressure treatment showed a metallic-like behaviour down to 4.2 K.