Evolution of ferroelastic domain walls during phase transitions in barium titanate nanoparticles

Abstract

In this work, ferroelastic domain walls inside BaTiO 3 (BTO) tetragonal nanocrystals are distinguished by Bragg peak position and studied with Bragg coherent x-ray diffraction imaging (BCDI). Convergence-related features of the BCDI method for strongly phased objects are reported. A ferroelastic domain wall inside a BTO crystal has been tracked and imaged across the tetragonal-cubic phase transition and proves to be reversible. The linear relationship of relative displacement between two twin domains with temperature is measured and shows a different slope for heating and cooling, while the tetragonality reproduces well over temperature changes in both directions. An edge dislocation is also observed and found to annihilate when heating the crystal close to the phase transition temperature.

Structural Explanation of the Dielectric Enhancement of Barium Titanate Nanoparticles Grown under Hydrothermal Conditions

“…BCDI reconstructions for the BTO commercial sample are discussed elsewhere. [ 32 ] The hydrothermally synthesized BTO NPs reported here, have a much higher level of disorder. The locally tetragonal domains we find in the long‐range cubic nanoparticles are so small that the diffraction patterns overlap completely within a single broadened Bragg peak.…”

“…BTO NPs have been imaged before using this technique. [31][32][33] Figure 5a-d shows the BCDI reconstructions of the BTO ethanol, PG, butanediol, and 240 °C samples. We measured several nanocrystals from each set of synthesis conditions in our BCDI experiments, and the reconstructions shown here are representative.…”

The ferroelectric phase transition in a 500 nm sized single particle of BaTiO3 tracked by coherent X-ray diffraction

“…[17][18][19][20] Such information on 90°domain structures can be obtained simultaneously with the outer shape and size of a particle by using coherent X-rays as a probe. 21,22) Coherent X-rays with a spatial coherence length of several micrometers are available at third-generation (and later) synchrotron light sources like SPring-8. When coherent X-rays fully illuminate a crystalline particle, a Bragg diffraction pattern is created that contains information about the crystal's outer shape, size, and lattice misalignment; this pattern is referred to as a speckle hereafter.…”

“…In the case of BTO, focusing on the reflection corresponding to a 90°domain orientation and applying Bragg-CDI reconstruct the real image of the domain. 22) It should be noted that current analytical techniques do not provide complete information about domain arrangement and outer shape using the peaks split into two measured at room temperature. First, for typical ferroelectric crystals with sufficiently anisotropic (e.g.…”

“…c/a ⩾ 1 in tetragonal), the outer shape obtained from the Bragg reflection is not that of the entire crystal but only the domain corresponding to the reflection; because the Bragg-CDI technique limits the applicable reflection to the one. 22) Second, the reconstructed image's phase contrast (strain) contains information on both domain walls and dislocations according to Ref. 26; distinguishing between domain walls and dislocations is critical when discussing ferroelectric size effects.…”