Dielectric spectroscopy of a ferroelectric nematic liquid crystal and the effect of the sample thickness

• Published in: Journal of molecular liquids Vol. 387; p. 122566
• Main Authors: Erkoreka, Aitor, Martinez-Perdiguero, Josu, Mandle, Richard J., Mertelj, Alenka, Sebastián, Nerea
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2023
• Subjects: Dielectric spectroscopy; Ferroelectric nematic phase; Liquid crystals; Relaxation phenomena; Relaxation phenomena; Dielectric spectroscopy; Ferroelectric nematic phase; Liquid crystals
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2023.122566

The recently discovered ferroelectric nematic liquid crystals have been reported to exhibit very large dielectric permittivity values. Here, we report a systematic investigation of the dielectric behavior of a prototypical ferroelectric nematogen by varying the thickness of the parallel capacitor measuring cell. While in the non-polar high temperature nematic phase results show only slight differences due to slight variations of the alignment, the measured permittivity values in the ferroelectric nematic phase show a linear dependence on the cell thickness. It is also shown that the characteristic relaxation frequency decreases inversely proportionally to the thickness. The results are discussed in terms of three different available models based on different underlying mechanisms, accounting for cancellation of the probe electric fields by polarization reorientation or by ionic charges, or based on a recently proposed continuous phenomenological model. •Measured dielectric permittivity values show a clear dependence on the thickness of the measuring parallel plate capacitor.•The characteristic relaxation frequency is inversely proportional to the sample thickness.•The obtained data have been analyzed in terms of three different models based on distinct physical mechanisms.