A part of the pseudo-binary join Bi₂O₃– Bi₂Mn₄O₁₀of the ternary system Bi₂O₃– MnO – MnO₂was examined using thermo-analytical methods. Because Bi₂Mn₄O₁₀melts incongruently single crystals of up to 20 mm in diameter were grown by the top seeded solution growth method in the temperature range from about 1223 K to 1173 K. Single crystal neutron diffraction confirmed the principles of the crystal structure of Bi₂Mn₄O₁₀but 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.

Direct link: http://www.ijmr.de/MK110714