Domain Structure of NaNO₂

Abstract

The 180° domains along the b direction in NaNO₂ single crystals were observed by the etching method at room temperature. The domain boundaries lie parallel to (100). The virgin crystal prepared from the aqueous solution is almost of single-domain, but, after having once been heated above the Curie temperature, it has nearly the same domain structure as the crystal prepared from the melt. These domains were ascertained to be the ferroelectric ones from experiments with dc field. By the alkali etchant the positive end of the domain was more rapidly etched than the negative one, and nearly the contrary result was obtained for the acid etchant. The fact that the domain boundaries lie parallel to (100) would be intimately related with the thermal motion of NO₂⁻ radicals.