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 mesophases 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.