The Use of a Ternary System on the Limits of Solid Soutions

摘要

The first is reported by C.M.Schaudt and D.M.Roy showing the limit of composition is 3CaO Al1.93Fe0.07O3 at 1389℃. The second is reported by P.Tarte showing the limit is 3CaOAl1.80Fe0.20O3 at 1310℃. In addition, A.J.Majumdar reported that the replacement of Al3+ ions by Fe ions in 3CaO・Al2O3 is 6～8mol.% at 1325℃. A.E.Moore 0reexamied this experiment and mentioned that the disagreement of the limit of composition is related to the temperature at which the preparation were symthesized; the higher the temperature the lower the "3CaO・Fe2O3" comcentration. And she suggested that this fact is owing to the unstableness of "3CaO・Fe2O3" at high temperature although the phase diagram obtained by C.M.Schlaudt and D.m.Roy did not agree with it. All experiments mentioned above are supposed to e carried out in the system3CaO・Al2O3- "3CaO・Fe2O3". The present study aims to charify the influence of the preparating temperature and the mixing syxtem to the limit of solid solution. The system employed in this experiments were 3CaO・Al2O3- "3CaO・Fe2O3", 3CaO・Al2O3- 2CaO・Fe2O3, 3CaO・Al2O3-CaO・Fe2O3 and 3CaO・Al2O3-Fe2O3. Both mechanical mixing method and liguid mising method were used to prepare raw mixtures. The mixtures were pressed into pellets, hung by Pt chains in a silicon carbide resistance furnace on by one, heated at a definite temperature (1250° and 1370℃) and the quenched. Samples thus prepared were tested by X-ray powder diffracion method and the lattice parameters were obtained as shown in Fig. 4.The limits of solid solutions were abtained as shown in Fig. 5.These resutes shows the normal temperature-dependent solubility, the higher the temperature the higher the Fe2O3 concentration, and also shows that the limit of solid solution is much variable according to a kind of the systems in CaO-Al2O3-Fe2O3 ternary. The maxium solid solubility is appeared at the 3CaO・Al2O3- 2CaO・Fe2O3 system.