The temperature dependence of the specific heat of Bi1.8Pb0.3SR1.9CuOy
samples in the overdoped region has been measured between 1.5 and 8 K
. Specific-heat anomalies were observed at T-c in two superconducting
samples, while no anomalies were observed in a nonsuperconducting one.
The values of Delta C/gamma T-c were quite small in comparison to the
BCS value, and the electronic specific heat in the superconducting st
ate near T-c exhibited a weak temperature dependence. These findings a
re consistent with the impurity effects predicted by the model of d-wa
ve superconductors proposed by Sun and Maki. Furthermore, we found tha
t the Sommerfeld constant y increases with increasing doped carrier fr
om the superconducting region to the normal metal region,in contrast t
o the case of La2-xSrxCuO4.