An x-ray photoelectron spectroscopy investigation of highly soluble grain-boundary impurity films in hollandite

Abstract

X-ray photoelectron spectroscopy was used to detect an intergranular impurity film in two (BaxCsy)(MnzTi8−z)O16 hollandite samples sintered in argon and air, respectively. This impurity film is enriched in Cs and Ba, as a result of segregation during high-temperature processing. The Cs ions in the grain-boundary layer have a different chemical bonding state from that in the hollandite phase, as evidenced by a large chemical shift of the Cs 3d and Cs 4d levels. The chemical environment around the Ba ions in the intergranular film is also likely to be different from that in the hollandite. The presence of this grain-boundary film is responsible for the relatively high initial loss of Cs and Ba during the aqueous dissolution testing. © 2010, Wiley-Blackwell.