Pressure-Induced Amorphization in BaF2 Nanoparticles

Synchrotron X-ray diffraction (XRD) is performed on BaF2 nanoparticles to study the structural phase transition up to about 30 GPa under ambient temperature. We observed that the cubic structure in BaF2 nanoparticles is stable up to 6.8 GPa, a level much higher than that in bulk BaF2. Pressure-induced amorphization (PIA) occurs in BaF2 nanoparticles under compression, which results in a high-density amorphous (HDA) form. Upon pressure release, a low-density amorphous (LDA) form is maintained at ambient conditions. This study is the first to demonstrate that PIA and polyamorphism exist in BaF2 nanomaterials and that finite grain size plays a critical role in inducing PIA and polyamorphism.