On the Ferroelectric-like Behavior of Lithium Hydrazinium Sulfate (LHzS)

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Ferroelectricity in Li(N_2H_5)S0_4 was reported by Pepinsky et al.^<1)> The crystal is orthorhombic, with space group Pbn2_1, a=8.96_9Å, b=9,91_3Å, c=5.17_8Å, Z=4 molecular units/cell. A good hysteresis loop was observed from about -15℃ to 80℃. They could not detect any specific-heat anomaly between -120℃ and 250℃. In this note, we present the structural evidence in LHzS which is contradictory to the so far established concept of ferroelectricity. The crystallographic data was confirmed, and the structure projected on (001) was obtained. The atomic coordinates determined from Fourier map ρ(xy) are listed in Table I. At this preliminary stage of analysis, no information is given on Li atom. However, a general schemes of the structure is already apparent, as shown in Fig. 1. In LHzS structure, one S-O bond in each S0_4 tetrahedron has almost the same orientation, being directed along c-axis. The senses of these bonds are the same with respect to (001) plane, because they are related by the symmetry elements of the assigned space group, which do not reverse them. Chains of hydrazinium are found running parallel to c-axis, probably connected by a system of hydrogen bonds. Recently, the more accurate result of the three-dimensional structure analysis was reported by Van den Hende.^<2)> The x-and y-coordinate in his structure are in good agreement with our result.
社団法人日本物理学会の論文
1964-01-05