抄録
The linear and nonlinear dielectric constants and electroclinic coefficient of some antiferroelectric liquid crystals are simultaneously measured in various smectic phases, SmA, SmCα* and SmCA*. The critical behavior in the SmA phase near the SmA-SmCα* or SmA-SmCA* phase transition is well describable by the phenomenological theory of Landau type which is proved to be applicable to the SmA-SmC* phase transition. We can calculate the phenomenological coefficient concerning to the ferroelectric order parameter. It is found that the third-order nonlinear dielectric constant in the SmCA* phase shows a positive sign which is in contrast with a negative sign in the SmC* phase due to the Goldstone mode.
