Phase Transition in CsH_3(SeO_3)_2

概要

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Dielectric, pyroelectric, thermal, optical and crystallographic properties of CsH_3(SeO_3)_2 Were studied. Various pyroelectric tests indicate essentially no net spontaneous polarization below the Curie point, -128℃. Correspondingly, no ferroelectric hysteresis loop appears; D vs E curves are linear except for an impressive form having the critical field, E_c, in a narrow temperature range Just below the Curie point, T_c, under an applied ac field perpendicular to (100). The critical field increases with decreasing temperature and is given with sufficient approximation by an expression; E_c=2.3×10^4(T_c- T)^<1/2>V/cm. The dielectric constant, ε⊥(100), shows a peak at the Curie point, which shifts, to lower temperature on application of a biasing dc field. These dielectric results may well be interpreted as a field-induced transition phenomenon from an antiferroelectric state to a paraelectric one. The measurement of specific heat as a function of temperature yields δS=0.81cal/mole・deg. The upper phase has symmetry P_I ^^-and the cell dimensions are a_u =9.32_6Å, b_u=6.52_6Å, c_u =5.83_5Å. α_u=91.5°, β_u=105.1°, γ_u=91.1°. The lower phase also has symmetry P_I^^-, but superstructure along the c axis, i.e., c_i≒2c_u.
社団法人日本物理学会の論文
1965-09-05