Second-harmonic dielectric response of an antiferroelectric liquid crystal under dc electric fields.

Second-harmonic dielectric response under dc fields in an antiferroelectric liquid-crystal 4-(1-methyl-heptyloxycarbonyl)phenyl 4-octylcarbonyloxybiphenyl- 4-carboxylate (MHPOCBC) has been investigated. The second-harmonic response from the amplitude mode in the smectic- Calpha* phase was observed due to the symmetry breaking by the application of dc electric fields. A Landau theory was developed in order to analyze experimentally obtained frequency dispersions.

Pseudomorphic 2A--> 2M--> 2H phase transitions in lanthanum strontium germanate electrolyte apatites.

Apatite-like materials are of considerable interest as potential solid oxide fuel cell electrolytes, although their structural vagaries continue to attract significant discussion. Understanding these features is crucial both to explain the oxide ion conduction process and to optimise it. As the composition of putative P6(3)/m apatites with ideal formula [A(I)(4)][A(II)(6)][(BO(4))(6)][X](2) is varied the [A(I)(4)(BO(4))(6)] framework will flex to better accommodate the [A(II)(6)X(2)] tunnel component through adjustment of the A(I)O(6) metaprism twist angle (varphi).

Nonlinear dielectric spectroscopy in the smectic-A-smectic-C(*)(alpha) phase transition.

We performed nonlinear dielectric spectroscopy to study the dynamic properties near the smectic-A-smectic-C(*)(alpha) phase transition point of an antiferroelectric liquid crystal 4-(1-methyl-heptyloxycar- bonyl)phenyl 4-octylcarbonyloxybiphenyl-4-carboxylate (MHPOCBC). A Landau-type theory was developed in order to analyze the experimentally obtained frequency dispersions. From the experimental and theoretical results we successfully obtained the temperature dependence of the relaxation frequency of the soft mode in both the smectic-A and smectic-C(*)(alpha) phases, which gave direct evidence that the transition is brought about by soft mode condensation.

Observation of the soft-mode condensation in the Sm-A-Sm-C(*)(alpha) phase transition by nonlinear dielectric spectroscopy.

We have theoretically and experimentally studied the nonlinear dielectric response under large orientational fluctuations near the Sm-A-Sm-C(*)(alpha) phase transition point in a chiral smectic liquid crystal. The third-order nonlinear dielectric response due to the fluctuations was observed in the vicinity of the transition point. By using it, we have successfully observed the soft-mode condensation inducing the Sm-A-Sm-C(*)(alpha) phase transition.