X-Ray Study of the Phase Transition in K₂Mn₂(SO₄)₃

Abstract

By X-ray diffraction together with optical observation of domains, the space group of potassium-manganese langbeinite K₂Mn₂(SO₄)₃ was determined in the both high and low temperature phases. It is determined that K₂Mn₂(SO₄)₃ is of the space groups T⁴–P2₁3 and D₂⁴–P2₁2₁2₁ at room temperature and at −82°C, respectively. The lattice constant almost linearly decreases with decreasing temperature in the high temperature phase and splits into three orthorhombic axes at −72°C. The lattice constants a, b, c in the low temperature phase also linearly decrease with decreasing temperature.