High-temperature phase transitions inLiKSO4

Pressure Raman spectra of LiK0.8(NH4)0.2SO4

“…They ruled out the first interpretation on the basis that the relative intensities of 1 peaks change in all the phases, rather than only in theˇ-phase. Therefore, this variation was assigned to the SO 4 2 orientational disorder exclusively. 15 We believe that orientational effects alone cannot be responsible for the diversity of data obtained so far.…”

“…evaporation method at about 25°C. Contents of NH 4 C ions in the crystals were determined by a spectrophotometric method. Raman microprobe spectroscopy experiments were performed at room temperature in the backscattering geometry using 514.5 nm radiation from an argon ion laser for excitation.…”

Thermal Analysis and X-Ray Diffraction Study on LiKSO4: A New Phase Transition

“…A hysteresis of 3 K was only observed at the phase transition IV by electrical conductivity measurements (19), but it is not observed by IR re#ection spectra. Brillouin scattering (19), powder di!raction, thermal analysis (this work), or linear bi-refrigence (21). At low temperature, as the structure is more compact (the c-parameter remains practically constant, Fig.…”

Effect of Li Content on the DSC and Electrical Conductivity of (Li1-xKx)2SO 4 Mixed Crystals

“…Li2S 04 under goes a first-order phase transition from a low tempera ture monoclinic to a high temperature cubic (f.c.c.) phase at ~570°C [5], whereas K2S 04 undergoes a ß -* a transition from an orthorhombic (space group Pmcn) to a hexagonal (space group P63/mmc) phase at 587 °C [7], Lithium potassium sulfate undergoes at least two structural phase transitions above room temperature at 435 and 670°C [8 ], Its symmetry is hexagonal at room temperature and above 670 °C. The structure of the intermediate phase (435< T < 670°C) was proposed to be orthorhombic [9], while other authors suggested a mod ulated structure, commensurate between 435 and 470 °C and incommensurate between 470 and 670 °C [10].…”