Alkali feldspar, a framework silicate (K, Na)(Si3Al)04, is a common component in ceramic materials. The feldspar crystals commonly display exsolution lamellae, twins, and modulated structures. The boundaries between neighboring domains may cause stain energy. The domain structures cause heterogeneities both inside crystals and on crystal surfaces in aspects of structure, composition, and surface microtopography. Reactivity at domain boundary positions is different from the neighboring areas. More and more studies show the effects of microtopography on the surface reactivity. It is important to reveal the surface characters or microtopography of domain structures in crystals, and their effects on local reactivity.

Results from transmission electron microscopy (TEM) characterization show it contains exsolution lamellae (both K-rich and Na-rich lamellae) and twin domains in the Na-rich lamellae (Fig. 1A). Its SAED pattern shows reflections from both K-rich and Na-rich lamellae (Fig. B). Splitted reflections result from the Na-rich lamellae wiht twin domains related by (010) mirror plane, i.e., albite twin law.