Tunneling studies have been carried out on single crystals of Bi2Ca1−xSrxCu2O8+δ over a wide range of compositions wherein the hole concentration varies by a factor of 2.5. The 2Δ value varies between 25 meV and 75 meV over the composition range studied, but scales with 2Δ/kBTc≈9.5 throughout.
