THE INCOMMENSURATE PHASE OF LiKSO 4

The phase transitions of LiKSO 4 have been investigated by means of X-ray powder diffraction and thermal analysis above room temperature. It is established that the crystal structure of LiKSO 4 between the melting point and 675℃ is isostructural with the high temperature phase of α-K 2 SO 4 and its space group is probably P6 3 /mmc. Cooling below T i =675℃ , there appears an incommensurately modulated structure analogous to the incommensurate phase in K 2 WO 4 , K 2 MoO 4 , etc. The parameter κ changes with temperature from 0.492(640℃ ) to 0.500(470℃ ). At 470℃ , I→C phase transition (lock-in) takes place, after which the crystal structure becomes the superstructure lattice of the room temperature phase. At 439℃ the superstructure disappears yielding to the room temperature phase (P6 3 ).