Single crystal growth and characterization of mullite-type Bi2Mn4O10

Abstract A part of the pseudo-binary join Bi2O3–Bi2Mn4O10 of the ternary system Bi2O3–MnO–MnO2 was examined using thermo-analytical methods. Because Bi2Mn4O10 melts incongruently single crystals of up to 20mm in diameter were grown by the top seeded solution growth method in the temperature range from about 1223K to 1173K. Single crystal neutron diffraction confirmed the principles of the crystal structure of Bi2Mn4O10 but revealed much smaller distortions of the cation coordination polyhedra. In contrast to the anisotropy observed in other mullite-type Bi containing compounds, the linear thermal expansion of Bi2Mn4O10, as studied by means of dilatometry and X-ray powder diffraction techniques, is characterized by α11 > α33>α22 at room temperature. The relatively large expansion along the a-axis can be attributed to the two oxygen atoms bridging two corner shared MnO5 tetrahedral pyramids which alternate with the structural void between two adjacent Bi3+ cations.