Figure 2. Bi₂O₃ rich regions of Bi₂O₃–RO systems, as determined from high-temperature x-ray diffraction data.

Phases: Mon—monoclinic, C—cubic, b.c.c.—body-centered cubic, ?—unknown, Rh—rhombohedral, ss—solid solution, Liq—liquid

(A) Bi₂O₃–MgO

a—Second phase, possibly MgO.

(B) Bi₂O₃–CaO

a—Described by Aurivillius (1943) [7].

b—Cubic Bi₂O₃ ss starting to form,

c—Cubic Bi₂O₃ ss increasing; Mon Bi₂O₃ decreasing,

d—Mon Bi₂O₃ gone.

The 6:1 composition slow-cooled from 700 °C (after 107 hr soaking period) shows single phase Rh_ss. See table 1 for unit cell dimensions.

(C) Bi₂O₃–SrO

a—Described by Sillén and Aurivillius (1939) [8].

b—Rh_ss increasing; Mon decreasing. See table 1 for unit cell dimensions.

(D) Bi₂O₃–BaO

a—Described by Aurivillius (1943) [7].

b—Rh_ss increasing; Mon decreasing. See table 1 for unit cell dimensions.

(E) Bi₂O₃—NiO

a—Liq cools to b.c.c.

●—First heat

□—b.c.c. reheated

■—Superposition of ● and □.

▼ -Reheated sample cooled from liq to 780 °C

b—b.c.c. decomposing to Mon.

c—Cubic phase when cooled to room temperature shows b.c.c.

(F) Bi₂O₃—ZnO

a—No Mon detected.

b—ZnO detected only in specimen soaked 107 hr at 700 °C and then slow-cooled.

The two compositions studied indicate that the b.c.c. phase is stable and melts congruently.

Beyond this the diagram is conjectural.

G) Bi₂O₃—CdO

a—Possibly one of Sillén’s reported CdO—Bi₂O₃ phases [9].

b—Liq cools to b.c.c.

(H) Bi₂O₃—PbO

a—C_ss cools to b.c.c.

b—C_ss+ Liq cools to b.c.c.