A new synthetic route via a solid-state reaction, the crystal structure of 12SrO·Al2O3 (S12A7) incorporated with OH- ions, and the formation of oxygen radical anions in S12A7 have been examined. Investigations using X-ray powder diffraction and thermogravimetric and evolved gas combined analyses demonstrate that homogenization promoted by molten Sr(OH)2 hydrates and the presence of Sr-hydrogarnet precursors play crucial roles in the formation of S12A7. Rietveld analyses confirm the lattice framework of S12A7 has a structure identical to that of the nanoporous crystal 12CaO·7Al2O3 (C 12A7, a mayenite structure) and demonstrate that two Sr2+ ions (pole Sr2+ ions) on the S4 axis of a cage displace toward the cage center owing to the accommodation of an OH - ion. An electron paramagnetic resonance study demonstrates that oxygen radical anions, O2- and O-, are generated in the cages with concentrations on the order of 1020 cm-3 each by oxygen annealing. From the g-values observed at 77 K, the oxygen radical anions are interpreted as being sandwiched between the two pole Sr2+ ions rather than adsorbed on one side.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Chemistry