The switching current behavior and the complex dielectric constant under DC
electric bias field and domain structures of an antiferroelectric liquid c
rystal, 4-(1-methylheptyloxycarbonyl) phenyl 4'-octyloxybiphenyl-4-carboxyl
ate (MHPOBC), were investigated as a function of optical purity and cell th
ickness, and the ferrielectricity of the chiral smectic C-beta phase (SmCbe
ta*) was discussed. Optically pure samples show two-step decrease in the re
al parr of complex dielectric constant with increasing DC bias field. The f
irst decrease corresponds to the suppression of the ferroelectric Goldstone
mode, which is also suppressed by decreasing cell thickness. The second st
ep, which is observed even in the chiral smectic C-alpha phase (SmCalpha*),
corresponds to the suppression of a new relaxation mode induced by DC elec
tric bias field. Three peaks of the switching current were observed in SmCb
eta* and also in the lower-temperature region of SmCalpha*. Temperature dep
endence curves of the peak positions are continuously connected together at
the phase transition temperature between SmCbeta* and SmCalpha*. It can be
said that the antiferroelectricity of SmCalpha* is conserved in SmCbeta*,
and that the ferrielectricity of SmCbeta* may consist of the ferroelectrici
ty of SmC* and the antiferroelectricity of SmCalpha*. Striped domains obser
ved in SmCbeta* after removing the DC electric bias field can he considered
to be the SmCalpha* phase.