Evolution of a ferroelastic domain structure in an incommensurate phase of barium sodium niobate (Ba2NaNb5O15)

Abstract

Features of a ferroelastic domain structure in an incommensurate phase of barium sodium niobate [${\mathrm{Ba}}_2$ ${\mathrm{NaNb}}_2$ ${\mathrm{O}}_{15}$ (BSN)] that appear in the cooling process were investigated by means of a transmission electron microscope. The in situ observation revealed that there exists an abrupt change in the domain structure around 503 K. The ferroelastic domain structure above 503 K basically consists of two types of 1q ferroelastic microdomains with a size of about 20 nm while below it large ferroelastic domains with flat domain boundaries are formed.