• MgO-”FeO”-SiO2

FeO and MgO showing a solid soln

Fig. 6.59. System MgO-”FeO”-SiO2 including binary systems.

Fig. 6.57. System MgO-”FeO”-SiO2 (oxide phases in equilibrium with metallic iron) (after E. F. Osborn and A. Muan, Phase Equilibrium Diagrams of Oxide Systems. American Ceramic Society, Columbus, Ohio, 1960).

SiO2

MgO FeO

2900°C

L

2700°C

L

L+M

2000°C

Magnesiowustite

1870°C

1860°C

L+MM

solidsolubility

1800°C

Mag

nesi

owus

tite

+Fo

rste

rite

-Fay

alite(

Oliv

ine)

M+O M+L

O+L

P+L

O+P

M+O

O+L

X+L

1550°C

X+L

M+L

M+O

O+L

X+P

O+PP+L

1527°C

two pts meet at 1543°C

T+L

P+T

O+P

M+O

M+L

O+L

P+L

1450°C

T+P+L and O+P+L meet at 1305°C, and P+L disappears

pyroxene (P) is (MgO,FeO)SiO2

cristobalite (X) transformed to tridymite (T) at 1470oC

P L

T

O

T

P

O+L

T decrease

M+L

• the relation between the structure of a ternary diffusion couple and the phase diagram