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 YBO3/Eu3+, GdBO3, and EuBO3, respectively, up to 41 GPa at room temperature using a diamond-anvil cell. Pressure-induced amorphization was observed in hexagonal GdBO3 with a significant compression along the c-axis. Compared to the ions of the distorted GdBO3 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 YBO3/Eu3+ and GdBO3 are 329 and 321 GPa, respectively, which are more than 90% larger than that of EuBO3 (167 GPa) and are presumably attributed to Gd3+ and Y3+ with a high density of d valence electrons.