INVESTIGADORES
SERQUIS Adriana Cristina
artículos
Título:
High temperature thermodynamic properties, orthorhombic/tetragonal transition and phase stability of GdBa2Cu3Oy and related R123 compounds
Autor/es:
F. PRADO; A. CANEIRO; A SERQUIS
Revista:
PHYSICA C - SUPERCONDUTIVITY
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 1998 vol. 295 p. 235 - 246
ISSN:
0921-4534
Resumen:
Thermogravimetric measurements of the equilibrium oxygen partial pressure (p(O2)) as a function of temperature and oxygen content have been made on GdBa2Cu3Oy (Gd123) within the range 3 × 10-4 atm ≤ p(O2) ≤ 1 atm and 450°C ≤ T ≤ 800°C. The partial molar entropy ΔS̄(O2) and enthalpy ΔH̄(O2) of solution of oxygen in Gd123 are evaluated and discussed. The p(O2) data on Gd123 are compared with measurements performed on NdBa2Cu3Oy (Nd123) at 800°C and literature data for YBa2Cu3Oy (Y123) at 600°C and 800°C. The orthorhombic/tetragonal transition temperature (TO/T) for Gd123 and Nd123 as a function of the oxygen partial pressure (1 × 10-3 atm ≤ p(O2) ≤ 1 atm) has been determined by high temperature X-ray diffraction (HTXRD). The oxygen content values for the O/T transition (yO/T) at several p(O2) values for Gd123 and Nd123 have been determined by means of thermogravimetric measurements. The obtained data in the y-T diagram supports the applicability of the quasichemical approximation in describing the O/T transition of Gd123 and Nd123 compounds. The effect of the R atom (R = Y, Gd, Nd) ionic size on the oxygen stoichiometry and phase stability of R123 compounds at high temperature is discussed, and a possible explanation is proposed which accounts for the lattice mismatch between Ba-O and CuO2 layers.