Study of Phase Transitions in Barium Titanate - Liquid Crystal Nano-colloidal Suspensions

A high-resolution ac-calorimetric study of the isotropic to nematic (\textit{I}-\textit{N}) and the nematic to smectic-\textit{A} (\textit{N}-Sm\textit{A}) phase transitions in nano-colloidal suspensions of Barium Titanate (BaTiO$_{3}$) in the liquid crystal (LC) octylcyanobiphenyl (8CB) as a function of BaTiO$_{3}$ concentration is reported. Heating and cooling scans were performed for all samples ($0.1 $ - $1.4$~wt\% of BaTiO$_{3}$ and pure 8CB) over a wide temperature range well above and below the two transitions. Both the \textit{I}-\textit{N} and the \textit{N}- Sm\textit{A} transitions evolve in character and have their transition temperatures shift lower as the wt\% of BaTiO$_{3}$ increases. Increasing hysteresis with increasing concentration is also observed at the \textit{I}- \textit{N} transition between heating and cooling scans within the two- phase \textit{I}+\textit{N} coexistence region. These results will be contrasted with other LC colloidal dispersion systems.