were grown by a floating-zone method. Samples bearing O
2
or H
2
ions were prepared by heating C12A7 powders or
single crystal in dry O
2
or dry H
2
atmosphere
[10,13 – 15]
The concentrations of O
2
and O
2
2
ions were measured at
77 K by EPR
[13,16]
, while the entrapped H
2
ion
concentrations were evaluated by a combined use of SIMS
and NMR
[10]
. Samples entrapping electrons instead of free
O
2
2
were prepared by heating a sealed silica glass
containing C12A7 single crystals
[17]
with metal Ca shots
at 700
8
C
[18]
. The thermionic emission of O
2
and H
2
ions
was measured by a time-of-flight mass-spectrometer