UC Davis

Temporal fluctuations in functional materials are critical for both phase stability and transformation processes. In these materials, nanoscale fluctuations play a pivotal role in mesoscale phenomena, such as domain reorientation and domain wall nucleation. Investigating the dynamics of these fluctuations is essential for a fundamental understanding of the landscape of domains and for enhancing the ability to tune and stabilize them for technical applications. In this thesis, I focus on the transformation of ferroelectric domains in BaTiO3 by examining the fluctuations of in-plane (a/b) domains. To probe the relevant spatial and temporal scales necessary for studying fluctuation dynamics, I employed a synchrotron-based coherent scattering technique known as x-ray photon correlation spectroscopy (XPCS). The primary objective of this research was to compare dynamic fluctuations among different types of domains during phase transitions, complementing existing studies on other domain configurations in BaTiO3. The XPCS results revealed that a/b domain fluctuations accelerate as phase transitions approach, a behavior also observed in a/c domains. Furthermore, this thesis explores the q-dependence of fluctuation behavior. I first examined whether similar fluctuation trends occurred across different orders of domain scattering peaks and also investigated potential q-dependence of fluctuations within a single peak. Analyzing various regions of q-space offers deeper insights into different aspects of domain configuration, such as domain walls. This investigation into the dynamic behavior of ferroelectric domains contributes to our understanding of the driving forces behind domain transformations and aids in optimizing the switching and stability of domains.