Abstract
The crystal structures and their changing trend in the strontium-bismuth-oxide system are critical for the studies of the related systems and their applications. The crystal structure of Sr
Bi
O
was obtained for the first time in the space group of R3[combining macron] with a huge unit cell of a = b = 25.1146(19) Å and c = 18.3685(16) Å and all bismuth ions are Bi
forming [BiO
] trigonal pyramids. Sr
Bi
O
is a key compound for the structural change trend in the SrO-Bi
O
binary oxide system at 1000 °C. With a decrease in the bismuth content, its valence state changes from +3 to +5 and Bi-O polyhedra changes from connected to isolated before Bi(v) appearance. In the system, the boundary of the solid solution β-phase (Sr
Bi
O
) at 900 °C was also determined accurately as 0.770 ≤ x ≤ 0.862, experimentally.