Determination of standard enthalpies of formation of member oxides in the Pb system

• Published in: Physica. C, Superconductivity Superconductivity, 1994-05, Vol.225 (1), p.127-135
• Main Authors: Idemoto, Yasushi, Shizuka, Kenji, Fueki, Kazuo
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cuprates superconductors (high tc and insulating parent compounds); Exact sciences and technology; High-Tc compounds; Physics; Properties of type I and type II superconductors; Superconductivity; Thermodynamic properties
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/0921-4534(94)90336-0

The heats of solution of four kinds of superconducting oxides, (Pb, Cu) (La, Sr) 2CuO y (Pb−1201), (Pb, Cu)Sr 2(Y, Ca)Cu 2O y (Pb-1212), (Pb 2, Cu) (La, Sr) 2CuO y (Pb-3201), (Pb 2, Cu)Sr 2(Y, Ca)Cu 2O y (Pb-3212), and their related oxides in the Pb system were determined by means of a multicalorimeter, and the heats of formation Δ H of complex oxides from reference simple oxides were calculated. The enthalpies of formation Δ f H O were also calculated. The heats of formation in terms of mole of atoms, Δ H R, were calculated by dividing Δ H by v, the number of atoms in a formula unit, and the chemical stability of each complex oxide was discussed. It was found that the 120 and 1212 phases treated in high oxygen pressure are stable, whereas the 3201 and 3212 phases are less stable than the former two.