Influence of the synthesis method on the structure and electrical properties of Sr1-xKxGeO3-x/2

The high oxide ion conductivities recently reported in Na- and K-doped strontium silicates and germanates, make them potentially suitable for different electrochemical applications. In this work, the structure, microstructure and electrical properties of Sr1-xKxGeO3-x/2 (x=0.0, 0.1, 0.15 and 0.2) compounds have been re-investigated. The materials have been prepared by conventional ceramic and freeze-drying precursor methods. Different phases are stabilized depending on the synthetic method and the sintering temperature used. Samples prepared by freeze-drying at 700 degrees C exhibit a triclinic structure, which transforms to a mixture of monoclinic and trigonal related phases on heating to 1000 degrees C. The presence of some broad diffractions peaks, which are not fitted in the Rietveld analysis, indicates the existence of an amorphous or low-crystalline phase (ACn) that have been quantified by an external standard procedure (G-factor approach). The homogeneity and chemical composition of the samples were checked by scanning electron microscopy combined with energy dispersive spectroscopy (EDX). The total conductivity of these materials was studied by impedance spectroscopy. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.