The effects of oxygen partial pressure (p
O
2
) up to 400 atm on the generation of active oxygen
radicals in 12CaO·7Al2O3 (C12A7) was examined using a hot isostatic pressing technique.
Concentrations of superoxide (O2
-) and oxygen anion radicals (O-), which were analyzed
from a combination of electron paramagnetic spin resonance (EPR) and Raman spectroscopy,
increased with p
O
2
. The total concentration of the radicals reached 1.7 × 1021 cm3, which is
comparable to the theoretical maximum, confirmed that dominant radical incorporation
process is O2- (cage) + O2 (atmosphere) → O- (cage) + O2
- (cage). The radical incorporated
C12A7 has a large magnetic susceptibility that obeys Curie's law down to 2.5 K without
magnetic ordering, although a weak exchange interaction was suggested by the line
narrowing of the EPR signal.
A new synthetic route via a solid-state reaction, the crystal structure of 12SrO • 7Al 2 O 3 (S 12 A 7 ) incorporated with OHions, and the formation of oxygen radical anions in S 12 A 7 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 S 12 A 7 . Rietveld analyses confirm the lattice framework of S 12 A 7 has a structure identical to that of the nanoporous crystal 12CaO • 7Al 2 O 3 (C 12 A 7 , a mayenite structure) and demonstrate that two Sr 2+ ions (pole Sr 2+ ions) on the S 4 axis of a cage displace toward the cage center owing to the accommodation of an OHion. An electron paramagnetic resonance study demonstrates that oxygen radical anions, O 2 and O -, are generated in the cages with concentrations on the order of 10 20 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 Sr 2+ ions rather than adsorbed on one side.
12SrOெ7Al 2 O 3 S12A7 is a meta-stable phase in the system of SrO-Al 2 O 3 and has the isostructure with 12CaOெ 7Al 2 O 3 C12A7 , which is composed of sub-nanometer-sized cages with oxygen ions loosely encaged in the cages. This letter reports fabrication of polycrystalline thin films of insulating and metallic S12A7 electride thin films. The as-crystallized film was an electrical insulator, while light-induced persistent electronic conduction with a conductivity of Ĭ1j10 3 Sெcm 1 at 300 K was realized in proton-implanted films. Higher conductivities of Ĭ270 Sெcm 1 were attained in the films subjected to a reduction treatment using an oxygen deficient amorphous film deposition. These behaviors are similar to those observed on C12A7. The present results suggest that S12A7 is another candidate material to explore electronic functions originating from a nanoporous structure embedded in a crystal structure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.