Refined Crystal Structure of LiNH₄SO₄Including Hydrogen Atoms in Phases II and III

Structural properties in mixed LiK1−(NH4) SO4 (x= 0, 0.06, and 1) crystals by nuclear magnetic resonance

“…(x = 0, 0.06, and 1) single crystals at room temperature was determined with an X-ray diffractometer system (Bruker AXS GMBH) at the Korea Basic Science Institute. The structures and the lattice constants of the LiKSO 4 and LiNH 4 SO 4 crystals are consistent with previous results [2,16]. The LiK 0.94 (NH 4 ) 0.06 SO 4 crystal obtained here has a hexagonal structure with cell parameters a = 5.153 Å, c = 8.641 Å, and V = 198.76 Å 3 .…”

“…The relationship between up and down along the pseudo-trigonal axis is 1:1 in LiNH 4 SO 4 . This relationship explains the different spontaneous polarization directions of the two compounds at room temperature, parallel to the trigonal axis in the LiKSO 4 and normal to the pseudo-trigonal axis in LiNH 4 SO 4 [16].…”

“…The structure of LiNH 4 SO 4 is orthorhombic with the space group Pc2 1 n and the lattice constants are a = 5.280 Å, b = 9.140 Å, and c = 8.786 Å in the temperature range 283 K < T < 459 K (Phase II) [16]. This structure consists essentially of six-membered rings typical of a tridymite framework that is made up of tetrahedral LiO 4 and SO 4 groups.…”

“…The layers of the six-membered rings form channels along the axis in which the NH 4 groups are located. The NH 4 groups lie approximately at the centers of the large cavities in the tetrahedral framework [16,23]. The structure of LiNH 4 SO 4 is characterized by the alternate rotation in the same direction of each tetrahedron, layer by layer, as shown in Fig.…”

Structures and thermal stability of the α-LiNH4SO4 polytypes doped with Er3+ and Yb3+

“…Above 460 K the corresponding ferroelectric-paraelectric transition to a crystal structure with the space group Pmcn takes place (Itoh et al, 1981). Below 285 K, it undergoes a ferroelectric-ferroelastic phase transition with a final monoclinic phase (P2 1 =c; Mashiyama & Kasano, 1993). Very recently, this non-polar and ferroelastic phase has been identified as a ferroaxial crystal structure (Hlinka et al, 2016).…”