The techniques used in the Tc measurements on the
CsBi-GIC's were nearly the same as those used for the
KHg-GIC's, described in Section 
.
There were several differences, however. One was that the
CsBi samples were routinely cleaved before the Tc
measurement so that any transition observed would be due to
the bulk of the sample, and not a spurious effect arising
from alloy adsorbed on the surface. Lagrange and coworkers do
not report whether they cleaved their samples or not.
KHg-GIC's very rarely had any adsorbed alloy since their
intercalation is accomplished through a vapor-phase reaction,
in contrast to the contact reaction necessary to intercalate
the MBi-GIC's. Therefore, KHg samples were not generally
cleaved before Tc measurements.
Because cleaving is a difficult operation to perform in the
glovebox on small samples, the CsBi-GIC's were cleaved in
air. Handling in air was also necessary to perform the
weight-uptake measurements described in Section .
Because of the compounds' excellent stability in air,[145] the brief exposures to
air were not thought to influence the superconductivity
experiments. The work of the Nancy group does not state
whether their samples were exposed to air before the
low-temperature experiments.
The CsBi-GIC's were place in glass ampoules for the
low-temperature experiments. They were not fixed in metal
sample-holders as the KHg-GIC's were [See Section
], though, because no critical field measurements were
performed on them. The inductive Tc measurements
were performed on the CsBi-GIC's in the same manner as on the
KHg-GIC's [See Section ]. The temperature range
of the inductive measurements was from 4.2 K to about 0.4 K,
just as for the KHg experiments.
The air stability of the CsBi compounds allowed resistive Tc measurements to be performed easily on them. Contacts were made with silver paint on the edges of the GIC in a standard four-probe geometry. The samples were then encapsulated in a cell filled with helium gas for good thermal contact at low temperatures. Both zero-field temperature sweeps and fixed-temperature field sweeps were performed on CsBi alpha- and alpha + beta-phase samples. The temperature range of the resistive measurements was from liquid helium temperature (4.2 K) to about 1.1 K. Current densities used were on the order of 10-1-10-2 A/cm2. The results did not depend on the current density employed. The values of the normal-state resistivity obtained from the temperature sweeps were estimated to be uncertain by about 25% due to remanent fields in the Bitter magnets used for the Shubnikov-de Haas measurements.