Structural properties in mixed LiK1−x(NH4)xSO4 (x = 0, 0.06, and 1) crystals by nuclear magnetic resonance

LiK1−x(NH4)xSO4 (x = 0, 0.06, and 1) mixed crystals were grown using the slow evaporation method, and their lattice constants were determined by X-ray diffraction. In order to determine the effects of the NH4 concentration on the phase transitions and the physical properties of mixed LiK1−x(NH4)xSO4 crystals (x = 0.06), we compared its NMR spectra and relaxation times with those of pure LiKSO4 and LiNH4SO4 crystals. After the partial replacement of potassium ions by ammonium ions, the ammonium ions occupy the same locations in the lattice as the potassium ions. The presence of the NH4 ions stabilizes the trigonal structure and prevents the breaking of trigonal symmetry at low temperatures. The main effects produced by the substitution of potassium ions with ammonium ions are the variations of the phase transition temperatures and the absence of ferroelastic properties.

Highlight
► The effects of the NH4 concentration on the phase transitions and the physical properties of LiK0.94(NH4)0.06SO4.
► After the partial replacement of K by NH4, the NH4 occupy the same locations in the lattice as the K.
► The variations of the phase transition temperatures and the absence of ferroelastic properties.