BaZr 0.85Me 0.15O 2.925 (Me=Y, In and Ga): crystal growth, high-resolution transmission electron microscopy, high-temperature X-ray diffraction and neutron scattering experiments

Abstract

Nanocrystalline BaZr 0.85Me 0.15O 2.925 (Me=Y, In and Ga) and also undoped BaZrO 3 powder samples with crystallite sizes of D vol=7 nm were prepared using a sol–gel-type hydrolysis in microemulsion-provided nanoreactors. High-resolution transmission electron microscopy (HR-TEM) and X-ray spectrochemical analysis were applied to investigate morphological and structural parameters of the nanosized ceramics. The original powder samples consist of agglomerated nanoscaled spherical crystallites with sizes from 5 to 10 nm in diameter. By structure imaging, the cubic phase of BaZrO 3 was recognised. In the case of the yttrium-doped zirconate, by means of local sensitive EDXS measurements, the evidence is found for an enrichment of the dopant ions in the interfaces of the crystallites, i.e. in the grain boundaries. The effect of dopant enrichment in the grain boundaries on proton diffusion was investigated by neutron scattering experiments, measuring a nanocrystalline sample and a microcrystalline sample as reference. In situ high-temperature X-ray crystallite growth studies were performed to check the influence of different dopant radii on crystallite growth.