Imaging microstructural dynamics and strain fields in electro-active materials in situ with dark field x-ray microscopy

Abstract

The electric-field-induced and temperature induced dynamics of domains, defects, and phases play an important role in determining the macroscopic functional response of ferroelectric and piezoelectric materials. However, distinguishing and quantifying these phenomena remains a persistent challenge that inhibits our understanding of the fundamental structure–property relationships. In situ dark field x-ray microscopy is a new experimental technique for the real space mapping of lattice strain and orientation in bulk materials. In this paper, we describe an apparatus and methodology for conducting in situ studies of thermally and electrically induced structural dynamics and demonstrate their use on ferroelectric BaTiO3 single crystals. The stable temperature and electric field apparatus enables simultaneous control of electric fields up to ≈2 kV/mm at temperatures up to 200 °C with a stability of ΔT = ±0.01 K and a ramp rate of up to 0.5 K/min. This capability facilitates studies of critical phenomena, such as phase transitions, which we observe via the microstructural change occurring during the electric-field-induced cubic to tetragonal phase transition in BaTiO3 at its Curie temperature. With such systematic control, we show how the growth of the polar phase front and its associated ferroelastic domains fall along unexpected directions and, after several cycles of electric field application, result in a non-reversible lattice strain at the electrode–crystal interface. These capabilities pave the way for new insights into the temperature and electric field dependent electromechanical transitions and the critical influence of subtle defects and interfaces.

X-ray free-electron laser based dark-field X-ray microscopy: a simulation-based study

“…This technique has been applied to characterize, for example, grain structure and dislocation networks in metals (Simons et al, 2015(Simons et al, , 2016Dresselhaus-Marais et al, 2021), dislocation toughening of ceramics (Porz et al, 2021), and ferroelectric domains and domain walls (Simons et al, 2016(Simons et al, , 2018Schultheiß et al, 2021). So far, DFXM has been applied at synchrotrons, with a time resolution of about 100 ms. On the one hand, this is sufficient to image some dynamic processes in situ, such as recovery in metals (Yildirim et al, 2020), dislocation motion close to the melting point in aluminium (Gonzalez et al, 2020;Dresselhaus-Marais et al, 2021), and structural transformations taking place in ferroelectrics during phase transitions (Ormstrup et al, 2020) or mechanical loading. While DFXM was recently demonstrated at an X-ray free-electron laser (XFEL), its time resolution measuring X-ray damage was still limited to 33 ms by the repetition rate of the source (Dresselhaus-Cooper, 2020).…”

Thermal and electric field stability of square-net domain patterns in barium titanate

“…The experiments were carried out on a commercially grown (Crystal GmbH, Germany) BaTiO 3 single crystal, grown via the top-seeded method and polished to 5 × 5 × 0.15 mm 3 . A custom-designed apparatus [13] was used to precisely control the temperature of the crystal and its applied electric field during the experiments. Optically transparent electrodes were applied to the 5 × 5 mm 2 faces by coating them with a thin layer (∼100 nm) of indium tin oxide (ITO) using magnetron sputtering at 100 • C for 30 min.…”

Pump-probe Dark-field X-ray Microscopy

“…DFXM is a full-field X-ray imaging technique and has been established as a tool for mapping orientation, and strain in deeply embedded structures [11]. This technique has also been employed for studying in situ dynamic processes such as dislocation movement as a function of temperature [15] and structural transformations during phase transitions in ferroelectric materias [16]. However, the pump-probe laser scheme incorporating the DFXM technique at synchrotron sources has not yet been reported.…”