Ferroelectricity in NH₄LiSO₄

Effect of deuteration on the electrical conductivity, dielectric constant and phase transitions in LiNH4SO4

“…The temperature variation of dielectric constant indicated in the plot given by Mitsui et al [3]. The general dielectric behaviour of DLAS with temperature is found to be the same as that of LAS with the difference that the peak heights for the former (85 and 50 at -l.~ e and 191 ° e , respectively) are slightly smaller.…”

“…The value of the room temperature dielectric constant of LAS is found to be the same as that reported previously [31. The reason for the low values of the dielectric maxima observed at the transition pOints in the previous study on LAS due to Mitsui et al [3) might have been due to a higher heating rate or due to the use of a bridge (which requires repeated balancing) instead of a direct reading instument for capacitance measurements.…”

“…Mechanisms of phase transitions and of electrical transport in the crystal are discussed. In this letter we present the fust report on the effect of deuteration on the electrical conductivity, dielectric constant and phase transitions in lithium ammonium sulphate (LAS) which is an extremely interesting room temperature ferroelectric material exhibiting two phase transitions of the fust order at atmospheric pressure with symmetry changes: phase I (Pnam) (paraelectric) 186.5°C I phase II (Pna2 1 ) (ferroelectric) l[S phase III (P2./a) (ferroelastic) [1][2][3][4][5][6][7][8][9]. Recent investigations on this material include the NMR studies at high pressure [10,11].…”

Study on the structural properties and relaxation mechanisms in LiRb1−x(NH4)xSO4 (x=0, 0.5, and 1) mixed crystals by 1H, 7Li, and 87Rb nuclear magnetic resonance

“…A large number of studies have examined the properties of the different phases of LiNH 4 SO 4 , with the ferroelectric behavior of the room temperature phase attracting particular attention. LiNH 4 SO 4 is an extremely interesting material that undergoes four phase transitions, at 459.5 K ( ¼T C1 ), 284.5 K ( ¼T C2 ), 133 K (¼ T C3 ), and 27 K ( ¼T C4 ) [6][7][8][9]. These four transitions of LiNH 4 SO 4 single crystals separate five phases denoted by I, II, III, IV, and V in order of decreasing temperature.…”

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

“…Several studies have examined the properties of the different phases of LiNH 4 SO 4 , with the ferroelectric behavior of the room-temperature phase attracting particular attention. LiNH 4 SO 4 undergoes four phase transitions, at 459.5 K (=T C1 ), 284.5 K (=T C2 ), 133 K (=T C3 ), and 27 K (=T C4 ) [11][12][13][14]; these four transitions separate five phases, denoted as I, II, III, IV, and V (in order of decreasing temperature). The symmetry of the high-temperature phase above 459 K has been identified as orthorhombic Pmcn (mmm).…”