LaPO4 Mineral Liquid Crystalline Suspensions with Outstanding Colloidal Stability for Electro-Optical Applications

Mineral liquid crystals are materials in which mineral's intrinsic properties are combined with the self-organization behavior of colloids. However, the use of such a system for practical application, such as optical switching, has rarely been demonstrated due to the fundamental drawbacks of colloidal systems such as limited dispersion stability. Studying colloidal suspensions of LaPO4 nanorods, it is found that drastic improvement of colloidal stability can be obtained through a transfer of particles from water towards ethylene glycol, thus enabling the investigation of liquid crystalline properties of these concentrated suspensions. Using polarization microscopy and small-angle x-ray scattering (SAXS), self-organization into nematic and columnar meso-phases is observed enabling the determination of the whole phase diagram as a function of ionic strength and rod volume fraction. When an external alternative electric field is applied, a very efficient orientation of the nanorods in the liquid-crystalline suspension is obtained, which is associated with a significant optical birefringence. These properties, combined with the high colloidal stability, are promising for the use of such high transparent and athermal material in electro-optical devices.