Ferroelectric Phase Transition in Microcrystals

The ferroelectric-paraelectric phase transformation in NaN${\mathrm{O}}_2$ microcrystals (size about 5 nm) has been investigated by differential thermal analysis. Single-domain particles exhibit spontaneous polarization irrespective of their microsize. The transformation temperature, $T_c$, of the interior of the particles remains unaffected by their dimension, whereas $T_c$ of the surface monolayer is lowered by a few degrees.