title: Capturing heterogeneous nucleation of nanoscale pits and subsequent crystal shrinkage during Ostwald ripening of a metal phosphate.
abstract: It has been generally accepted that crystal shrinkage during Ostwald ripening can be understood simply as a reverse process of crystal growth, and as a result, little attention has been paid to shrinkage behavior. The entire microstructure of polycrystalline materials, however, forms as a consequence of both growing and shrinking crystals. Thus, scrutiny of shrinking characteristics in addition to growth aspects is essential for a complete understanding of the evolution of microstructure during Ostwald ripening. By capturing real-time in situ high-resolution electron micrographs at high temperature, we herein demonstrate the shrinkage behavior of nanocrystals embedded in a solid crystalline matrix during the ripening process of a metal phosphate. Unlike typical crystal growth behavior based on two-dimensional homogeneous nucleation, heterogeneous types of nucleation with nanoscale pits at solid-solid interfaces (or crystal edges) are observed to dominantly occur during shrinkage of the crystals. The findings of this study suggest that crystal shrinkage proceeds with a lower activation energy barrier than that of crystal growth, although both crystal growth and shrinkage take place at the same time during Ostwald ripening.
authors.affiliation: Graduate School of EEWS, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 305-701, Korea.
authors.forename: Sung-Yoon
authors.initials: SY
authors.lastname: Chung
authors.forename: Young-Min
authors.initials: YM
authors.lastname: Kim
authors.forename: Si-Young
authors.initials: SY
authors.lastname: Choi
authors.forename: Jin-Gyu
authors.initials: JG
authors.lastname: Kim
keywords: Ostwald ripening; dissolution; heterogeneous nucleation; in situ HREM; surface