Domain Switching Dynamics in [001]- and [111]-Poled Rhombohedral PMN-PT Single Crystals Through X-Ray Photon Correlation Spectroscopy

Relaxor-<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{PbTiO}_{3}$</tex> single crystals are distinguished by remarkable electromechanical properties, making them valuable for applications in ultrasound transducers. Although many studies have explained the high performance of these materials, real-time observation of dynamics remains challenging. In this study, we investigate correlation dynamics in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Pb}\left(\text{Mg}_{1 / 3} \text{Nb}_{2 / 3}\right) \mathrm{O}_{3}-\text{PbTiO}_{3}(\text{PMN}-\text{PT})$</tex> rhombohedral single crystals using X-ray photon correlation spectroscopy (XPCS). Two crystal orientations, [111] and [001], are examined under bipolar electric field to understand their polarization switching behavior. The correlation decay patterns are analyzed using the Kohlrausch-Williams-Watts (KWW) model, providing quantitative insights into the rate of nucleation and growth. XPCS measurements reveal significantly shorter relaxation times in the [001]-poled sample compared to the [111]-poled counterpart. This enhanced dynamics in the [001]-poled specimen correlates with superior permittivity and piezoelectric coefficient (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$d_{33}$</tex>), which indicates enhanced domain wall motion as interpreted through classical nucleation and growth mechanisms.