The oxygen-structure-property relationship in Bi-2212 is
a complicated one, and there remain some important grey
areas which need to be elucidated if full understanding of
the doping mechanisms in this system are to be achieved.
The results of the experiments described in this chapter have
successfully related differences in the diffuse scattering of
as-grown crystals to variations in the oxygen content of the
crystals, and have observed a dramatic transformation in shape
and intensity of the diffuse streaks of an oxygen rich crystal
by briefly annealing at 700
C. The change in line shape is
indicative of an ordering transition having taken place. The
combination of these two observations is strong evidence to
reason that oxygen ordering is the root cause of these diffuse
streaks. Such oxygen ordering effects are well known in the
other cuprate system Y-123, and are known to hold an important
influence over T
. Unfortunately, the information provided
here by the diffuse x-ray scattering measurements is not
sufficient on its own to establish the precise crystallographic
sites responsible. The exact location of the excess oxygen and
its role in the electronic properties of the system is an
important question, but one which still remains to be resolved.