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 K 2 Mn 2 (SO 4 ) 3 was determined in the both high and low temperatuare phases. It is determined that K 2 Mn 2 (SO 4 ) 3 is of the space groups T 4 -P2 1 3 and D 4 2 -P2 1 2 1 2 1 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.