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.

A comparative review of the aqueous corrosion of glasses, crystalline ceramics, and metals

“…Grain boundaries may also be enriched with highly soluble elements or formed as intergranular glassy phases, 109,110 thus leading to rapid initial dissolution rate during aqueous dissolution. 111 The bulk dissolution kinetics are significantly impacted by precipitation or new phase formation for crystals that do not exist in equilibrium with aqueous solutions at ambient temperature and pressure. The concentration-time curve is controlled by the precipitation of low solubility phase(s) (Fig.…”

Radioactive waste (RAW) conditioning, immobilization, and encapsulation processes and technologies: overview and advances

“…Among these high temperature (1000-1500°C) processes are the Sandia titanate-based ceramic [56], the Australian titanate-based ceramic "SYNROC" [57,58,59], the silicate-phosphate supercalcine ceramics [60], the alumina based tailored ceramics [61,62], the Pu pyrochlores [63]. Often in ceramics made by cold pressing and sintering or hot isostatic pressing, an intergranular glassy phase is produced during liquid phase sintering on the ceramic grain boundaries and the radionuclides preferentially migrate to the glassy phase(s) [64,65,66,67,68,69,70,71,72]. If the radionuclides are incorporated in the intergranular glassy phase(s), they have been found to leach at about the same rates as those from glassy wasteforms.…”

Ceramic Mineral Waste-Forms for Nuclear Waste Immobilization

“…The structural types of monazite, kosnarite (NZP), langbeinite and other ones were considered as matrices for the incorporation of simulated wastes containing f-elements and that also contain uni-, bi-, and trivalent elements involved in radiochemical processes [16,17,18,19,20,21,22,23,24,25,26,27]. Cold pressing and sintering, as well as hot isostatic pressing often result in ceramics containing an intergranular glassy phase with radionuclides preferentially migrating to the glassy phase [28,29,30,31,32,33,34,35,36]. The radionuclides that are incorporated in the intergranular glassy phase(s) will then have leaching rates at about the same order as those from a glassy waste-form.…”