Abstract
Domain walls have distinct properties from the bulk, and tailoring them to suit the needs for device applications is critical. Tungsten trioxide, WO3, is of great interest for device applications that make use of domain wall properties; it exhibits a phenomenologically rich sequence of phase transitions, virtually all of which are ferroelastic in character, resulting in many sets of domain walls at low temperatures, each with their own unique properties. Domain wall motion and its contribution to the piezoelectric response have been investigated in WO3 from 300 to 180 K using resonant ultrasound spectroscopy (RUS) and resonant piezoelectric spectroscopy (RPS), which showed that the 𝑃21/𝑛,𝑃 1, and 𝑃21/𝑐 phases give a piezoelectric response despite the bulk being nominally centrosymmetric. Second harmonic generation (SHG) confirmed that polarity was strongest within the domain walls, and additional weak signals were found in the domains. Domain wall mobility was investigated in the 𝑃𝑏𝑐𝑛,𝑃21/𝑛, and 𝑃21/𝑐 phases from 685 to 5 K. Domain walls in the 𝑃21/𝑛 and 𝑃1 were more mobile than those in the 𝑃𝑏𝑐𝑛 and 𝑃21/𝑐 structures, and soon after the 𝑃 ‾1 →𝑃21/𝑐 transition the walls become pinned at ∼140K.
