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| Title
| - Solid State Syntheses of 12SrO·7Al2O3 and Formation of High Density Oxygen Radical Anions, O− and O2−
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| Abstract
| - A new synthetic route allows the formation of a quasi-stable phase of S12A7 with a crystal structure comprising cages and extra-framework anions within. Accomodation of an OH− ion in a cage displaces two pole Sr2+ ions toward the cage center. O2− and O− radical anions can replace the OH− ion.
- A new synthetic route via a solid-state reaction, the crystal structure of 12SrO·7Al2O3 (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 (C12A7, 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.
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| Alternative Title
| - Syntheses of 12SrO·7Al2O3, Formation of O− and O2−
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