SPECIFIC-HEAT OF POLYCRYSTALLINE (HG,PB)BA2CA2CU3O8-C(DELTA NEAR T)

We have measured the specific heat of polycrystalline (Hg,Sb)Ba2Ca2Cu3 O8+delta between 60 K and 200 K with a calorimeter based on the standa rd continuous-heating method. The occurrence of an anomaly in C-p(T)/T peaking at T-c for these samples clearly shows that superconductivity is a bulk phenomenon in this type of compound. After subtraction of a fitted background, we deduce a value of Delta C-p/T-c approximate to 27 mJ/mole K-2 for a 15% Pb-doped sample containing approximate to 60% of Hg-1223. An as-prepared sample containing Hg0.8Pb0.2Ba2Ca2Cu3O8+de lta as the dominant phase shows a distinct anomaly in the specific hea t data at T-c = 130 K and at T-c = 115 K for a specimen cut from the s ame initial sample after oxygen annealing. The size and the shape of t he specific heat anomalies are very similar, irrespective of the value of T-c and thus the hole-doping level.