Specific heat measurements of high-Tc superconductor YBa2Cu3O7 between 78 K and 260 K

High-precision specific heat measurements of the single-phase high-Tc superconductor YBa2Cu3O7 have been performed in the temperature range between 78 K and 260 K. A distinct jump in the C/T vs. T plot, which is associated with the superconducting phase transition in this compound is observed at Tc = 91.8 K. The value of ΔC/Tc is estimated to be 48 ± 2 mJ/mol K2. The γ-value, the coefficient of the linear term in the specific heat calculated from the static susceptibility above Tc, is 36 ± 2 mJ/mol K2, which is comparable to the values for A-15 compounds. The ratio ΔC/γTc results in the value 1.33, which is close to 1.43, the weak-coupling BCS value. An anomalous large temperature variation of the Debye-temperature ΘD suggests the existence of anomalous phonon modes in this crystal structure