High-pressure x-ray diffraction study of YBO3/Eu3+, GdBO3, and EuBO3: Pressure-induced amorphization in GdBO3

Angle-dispersive synchrotron X-ray diffraction measurements were performed on vaterite-type YBO 3 /Eu 3+ , GdBO 3 , and EuBO 3 , respectively, up to 41 GPa at room temperature using a diamond-anvil cell. Pressure-induced amorphization was observed in hexagonal GdBO 3 with a significant compression along the c -axis. Compared to the ions of the distorted GdBO 3 phase, its anions may lose their long-range order prior to the cations at high pressures. Based on the experimental pressure-volume data, the obtained bulk moduli of YBO 3 /Eu 3+ and GdBO 3 are 329 and 321 GPa, respectively, which are more than 90% larger than that of EuBO 3 (167 GPa) and are presumably attributed to Gd 3+ and Y 3+ with a high density of d valence electrons.