X-RAY STUDY OF PHASE-TRANSITION IN K2MN2(SO4)3

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 D42-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. © 1978, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.