title: The influence of suspended nanoparticles on the Frederiks threshold of the nematic host.
abstract: In recent years, several papers reported an enhanced dielectric anisotropy when ferroelectric particles were suspended in a liquid crystal. These results seem to be sensitive to the liquid crystal used and the preparation method of the ferroelectric particles. In this paper, we compare different preparation methods of suspended barium titanate in two different liquid crystal hosts. As a control experiment, we followed similar preparation steps with non-ferroelectric silica particles. In all cases, we found a broadening of the optical Frederiks transition but no change in the dielectric anisotropy. Raman spectroscopy has been used to investigate the loss of tetragonal structure in the barium titanate as a function of milling time and particle size. As reported in the earlier literature, barium titanate does not exhibit a well-defined tetragonal crystal structure below a certain particle size and loses its ferroelectric features. This provides a simple rationalization for the absence of any dielectric enhancement.
authors: HP Laboratories, Long Down Avenue, Stoke Gifford, Bristol BS34 8QZ, UK. susanne.klein@hp.com
authors: Susanne
authors: S
authors: Klein
authors: Robert M
authors: RM
authors: Richardson
authors: Robert
authors: R
authors: Greasty
authors: Rhys
authors: R
authors: Jenkins
authors: Joseph
authors: J
authors: Stone
authors: Michael R
authors: MR
authors: Thomas
authors: Andrei
authors: A
authors: Sarua