Equilibrium phase diagram for the system PbO-CaO-CuO

Abstract

In order to obtain essential information on the formation process of the high-Tc phase in the Bi, Pb-Sr-Ca-Cu-O system, phase equilibria in the system PbO-CaO-CuO have been studied, mainly by x-ray diffraction analysis and thermal analysis. Temperature versus composition diagrams were established for the systems PbO-CuO(Cu2O) and PbO(PbO2)–CaO in air. Three invariant points were detected in these systems: a eutectic reaction (PbO + Ca2PbO4 = L) at 847 ± 6°C, a peritectic reaction (Ca2PbO4 = L + CaO) at 980 ± 2°C, and a eutectic reaction (PbO + CuO = L) at 789 ± 3°C. For the system PbO(PbO2)-CaO-CuO, subsolidus phase equilibrium in air was established. The liquidus was also examined at 780, 800, and 820°C, and a ternary (PbO-Ca2PbO4-CuO) eutectic point was detected at 772 ± 6°C.

Experimental study of phase equilibria in the systems PbO x -CaO and PbO x -CaO-SiO2

“…These new experimental data have been used by the present authors to optimize the thermodynamic models for this system using the computer system F*A*C*T. [21] The liquidus in equilibrium with air calculated using the new F*A*C*T model is presented in Figure 1 together with the present experimental results (Table I) and the results reported by Kitaguchi et al [12] This is a pseudobinary section at constant oxygen potential through the ternary system Pb-Ca-O. The system in air includes the compound Ca 2 PbO 4 , which melts incongruently at a temperature above [12] ); (2) liquidus in the Ca 2 PbO 4 primary field found at higher temperatures; and (3) higher eutectic temperature (over 850 ЊC (1123 K) vs 847 ЊC (1120 K) [12] ).…”

“…[3,10] The investigators of the system Pb-Ca-O in air [11,12] reported the existence of the incongruently melting compound 2CaO*PbO x , where x ϭ 1 [11] or x ϭ 2. [12] The existence of 2CaO*PbO 2 has been confirmed by others, [13,14,15] all of whom indicate that lead may be present in the 4ϩ as well as the 2ϩ states. This means that the system in air is not a true binary but part of the Pb-Ca-O ternary system.…”

“…Kuxman and Fisher [11] reported the compound Ca 2 PbO x contained Pb 2+ , while Kitaguchi et al [12] indicated lead to be present in the Pb 4+ state. To resolve these uncertainties, further investigations were undertaken in the present study.…”

Effect of CuO on the sintering temperature and piezoelectric properties of MnO2-doped 0.75Pb(Zr0.47Ti0.53)O3–0.25Pb(Zn1/3Nb2/3)O3 ceramics

“…However, at 5.0 mol% a second phase was formed along the grain boundary and the triple point of the specimen, as indicated by the arrowhead in Fig. 1(d), revealing that liquid phase sintering was responsible for the formation of the dense microstructure for the CuO-added specimens sintered at 850 • C. Moreover, since CuO and PbO form the eutectic point at approximately 790 • C [21], the second phase found in the specimen with x = 5.0 was considered to contain both CuO and PbO. All the specimens had a tetragonal perovskite structure and a homogeneous tetragonal perovskite phase was observed for the specimens with x ≤ 3.0.…”

Thermodynamic Optimisation of the Systems Cao-Pb-O and Pbo-CaO-SiO2

“…Thermodynamic properties of stoichiometric compounds in the PbO-CaO-SiO: system Kitaguchi et al [26]investigated this system in air using TG-DT A. The intermediate compound was reported [26] to be Ca2Pb04 (2CaO.Pb02); no Ca2Pb03 was found.…”