Heat capacity and thermal stability of Y_2BaCuO_5

摘要

Phases Y_2BaCuO_5 and YBa_2Cu_3O_7 belong to the system Y-Ba-Cu-O, which is well-known for unique high-temperature superconducting properties. In this contribution, we have studied in detail the Y_2BaCuOs phase, also known as a 'green phase' or 'Y-211', which is usually an accompanying phase in YBCO superconducting bulks. Morphology and chemical composition were studied using energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). Lattice parameters were refined by Rietveld analysis based on obtained XRD data. Simultaneous thermal analysis was employed to study thermal stability. The heat capacity and enthalpy increments were measured by physical property measurement system (PPMS) and drop calorimetry. Such data are of utmost importance for the phase equilibria study of the Y-Ba-Cu-O system and further improvement of bulk properties of HTS superconductors.