Synthesis and crystal structure of Sr3Bi2O6 and structure change in the strontium-bismuth-oxide system

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 Sr3Bi2O6 was obtained for the first time in the space group of R with a huge unit cell of a = b = 25.1146(19) A and c = 18.3685(16) A and all bismuth ions are Bi3+ forming [BiO3] trigonal pyramids. Sr3Bi2O6 is a key compound for the structural change trend in the SrO–Bi2O3 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 (Sr1−xBixO1+0.5x) at 900 °C was also determined accurately as 0.770 ≤ x ≤ 0.862, experimentally.