Ferroelectric particles in LC and polymer composite test devices

Zhen Gong; Christoph Ostwald; Nicolai M. Hoinka; Benedikt Mohr; Thomas Fuhrmann-Lieker; Alexander Lorenz

doi:10.1117/12.2530502

29 August 2019 Ferroelectric particles in LC and polymer composite test devices

Zhen Gong, Christoph Ostwald, Nicolai M. Hoinka, Benedikt Mohr, Thomas Fuhrmann-Lieker, Alexander Lorenz

Proceedings Volume 11092, Liquid Crystals XXIII; 110920U (2019) https://doi.org/10.1117/12.2530502
Event: SPIE Organic Photonics + Electronics, 2019, San Diego, California, United States

Abstract

Small, surface functionalized, Fe-doped LiNbO₃ (FeLN) particles were experimentally investigated. Planar thin-cuts (0.5 – 1 mm thick) of FeLN crystals have recently been investigated as field generating substrates in LC test devices. Here, realignment of the liquid crystal (LC) director can be locally driven with photovoltaic fields, generated by the substrates (surface-fields, generated via the bulk photovoltaic effect). Such samples can be exposed with tightly focused light beams and show unexpectedly high non-linear optical responses, light induced defect formation; some samples could even reversibly store patters inscribed by the use of light. Here, it is investigated how the use of field-generating crystals be pushed further. Small particles are still suitable to control LC realignments – at least to a certain amount. Small particles of Fe-doped LiNbO₃ and for reference also BaTiO₃ were integrated in test devices. The particles were prepared in a top-down approach, that is larger specimen of ferroelectric crystals were first crushed with mortar and pestle to obtain a powder. From these powders, dispersions of particles were fabricated by high energy ball-milling. A small amount of the powder together with an organic solvent (continuum medium) was placed in the milling jars of a planetary ball mill. A small amount of a surfactant was added – both use of a conventional surfactant and in-house synthesized, photochemically active species was investigated. The dispersions obtained were used to coat the surfaces of LC test cells and for doping of polymer films. The samples obtained show many interesting and sometimes unexpected properties.

Citation Download Citation

Zhen Gong, Christoph Ostwald, Nicolai M. Hoinka, Benedikt Mohr, Thomas Fuhrmann-Lieker, and Alexander Lorenz "Ferroelectric particles in LC and polymer composite test devices", Proc. SPIE 11092, Liquid Crystals XXIII, 110920U (29 August 2019); https://doi.org/10.1117/12.2530502

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