Mesomorphic Ceramics via Blade Coating of Lyotropic Nanorod Suspensions

Mesomorphic ceramics are inorganic polycrystalline solids with static liquid crystalline superstructures. Here, we fabricate mesomorphic ceramic thin films over centimeter length scales by blade coating nematic lyotropic suspensions of ZnO nanorods, followed by calcination. The coating velocity was optimized in the Laundau-Levich regime to obtain defect-free ceramics green bodies.  The resulting mesomorphic ceramic thin films are optically transparent with a smooth surface finish and exhibit in-plane birefringence of 0.075 ± 0.002. Form birefringence is shown to dominate over the intrinsic birefringence of ZnO. Uniaxial orientation of ZnO crystallites along the coating direction was confirmed by texture analysis and SEM imaging. The reported method to fabricate birefringent, mesomorphic ceramics is cost-effective, scalable, and expected to be broadly applicable to nematic lyotropic suspensions of various nanorods. Moreover, it could benefit diverse applications including thin-film electronics, optoelectronics, catalysis, and optics for high-power lasers.