Summary: | A modified AC method is developed for measuring the specific heat of very small high
quality single crystal samples of Y₁B₂C₃O6+x (Yttrium Barium Copper Oxide). The system
developed combines the original AC calorimetry method introduced by Sullivan et al. and the
thermal relaxation method by Bachmann et al. The modification involves the use of a
sapphire as substrate to support the crystal, heater and the temperature sensor. A complete
thermal analysis of the experimental setup is presented in addition to a detailed experimental
procedure for measuring the heat capacity of a small sample. Some experimentation with
diamond substrate is performed as well and compared with sapphire. Another feature added
to our AC calorimetry setup is a Dewar pressure regulation system. This was to minimize the
variations in the liquid bath temperature due to changes in ambient pressure. Our system also
allows for multiple sweeps, as bath temperature is monitored, from which the best sweeps
corresponding to the most stable temperature interval is chosen for further analysis.
Considering the different mathematical models developed so far for explaining the
behavior of the specific heat fluctuation of YBCO, our results seem to support the 3D XY
model near the transition temperature of 93.IK. From the heat capacity data our crystal
sample showed a transition width, ΔTc, of 0.45K, and a superconducting transition jump ACp,
of 6.1mJ/gK.
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