Thermal Properties of Tl₂Ba₂Ca₃Cu₄O₁₁₊δ Superconductor and Determination of the Optimal Processing

This research investigates the thermal properties of Tl₂Ba₂Ca₃Cu₄O₁₁₊δ high-temperature superconductor using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The study aims to understand the thermal behavior and optimize processing conditions for enhanced superconducting performance. A 40 mg sample was synthesized using a one-step solid-state reaction method and analyzed in air atmosphere from room temperature to 1200°C at a heating rate of 10°C/min. DSC analysis revealed four distinct exothermic peaks at 824°C, 839°C, 907°C, and 935°C, corresponding to superconducting phase formation, crystallographic transformations, phase decomposition, and structural breakdown, respectively. The optimal thermal processing window was identified as 820-840°C for controlled structural formation. TGA analysis demonstrated excellent thermal stability with total weight loss not exceeding 5% up to 1200°C. Specific heat capacity measurements identified two major thermal transitions: the first at 824°C (Cp = 10 J/g·°C) related to secondary phase melting, and the second at 933°C (Cp = 12 J/g·°C) corresponding to primary superconducting phase melting. These findings provide valuable insights into the optimal processing conditions for Tl₂Ba₂Ca₃Cu₄O₁₁₊δ, emphasizing the importance of precise temperature control to maximize phase purity, thermal stability, and superconducting performance.