Phase equilibria relationship in the FetO-TiO2-CaO-SiO2 system with CaO/SiO2 weight ratio of 1.2 at 1673K

Abstract

Phase equilibria relationship in the FetO-TiO2-CaO-SiO2 system with CaO/SiO2 weight ratio of 1.2 under argon atmosphere were identified experimentally at 1673K by employing high-temperature equilibration method followed by electron probe X-ray microanalysis (EPMA) and X-Ray Diffraction (XRD) measurements. It was found that there exist 7 crystal phases and 1 liquid phase in the system, and 19 different kinds of phase equilibria relationship exist among these 8 phases. The 7 crystal phases are as follows: kilchoanite (Ca3Si2O7), ulvöspinel (Fe3-xTixO4), pseudobrookite (FeO·2TiO2), ilmenite (FeTiO3), perovskite (CaTiO3), rutile (TiO2) and wüstite (FetO). By using L as the symbol for liquid phase, K for kilchoanite, U for ulvöspinel, B for pseudobrookite, I for ilmenite, P for perovskite, R for rutile and W for wüstite, the 19 phase equilibria relationships formed by these phases can be summarized as follows: 1) single L, 2) L + U, 3) L + R, 4) L + W, 5) L + K, 6) L + I, 7) L + B, 8) L + P, 9) L + R + P, 10) L + I + P, 11) L + B + I, 12) L + R + B, 13) L + U + W, 14) L + U + I, 15) L + U + P, 16) L + P + B, 17) L + U + I + P, 18) L + R + B + P, and 19) L + B + I + P. Finally, based on the above-determined phase equilibria relationship, a section phase diagram of the system at 1673K was constructed. From the constructed phase diagram, the evolution of phases caused by composition change can be seen graphically.