Pressure-induced structural evolution and amorphization in Eu3Ga5O12

Abstract

Crystal structural evolution of europium gallium garnet (Eu3Ga5O12; EGG) has been investigated by a combination of synchrotron x-ray diffraction, Raman scattering, and photoluminescence spectroscopy in a high-pressure diamond anvil cell. The cubic garnet EGG mostly collapses into an amorphous state upon compression to 85 GPa at room temperature. High-pressure Raman and photoluminescence spectra indicate that the amorphization process is related to the interaction and deformation of the tetrahedra GaO4 and octahedra GaO6 under compression, leading to the increase of the asymmetry of the local oxygen environment around the Eu3+ site with increasing pressures. The amorphization of EGG is associated with the overlapping of the tetrahedra and octahedra and the increase of the average coordination numbers of the Ga3+ ions in the amorphous state. X-ray diffraction spectra of EGG taken from a laser-heated diamond anvil cell demonstrate that the pressure-induced garnet-to-amorphous transition could result from the kinetic hindrance of a crystal-to-crystal phase transition at room temperature, rather than the decomposition reported earlier.

Pressure-induced amorphization of the Y3Ga5O12 garnet studied to 1 Mbar

“…The amorphization pressure of the YGG compares very well with the amorphization onset of other garnets as GGG (84(4) GPa) and GSGG (58(3) GPa )[14]. The anisotropic structural refinement of our single x-ray diffraction experiment at 50 GPa has previous conclusions[16] that establish that the mechanism of the PIA process in garnets is the result of a strong reduction of the inter YO 8 and GaO 4 polyhedral distances. Such a reduction produces and overlapping of both coordination blocks that results in a PIA.…”

“…In this case the combination of x-ray diffraction, Raman spectroscopy and Eu 3+ luminescence serve to conclude that the PIA process is due to the overlapping of the Ga tetrahedra and octahedra [16]. That overlapping gives rise to an increase of the asymmetry of the oxygen local environment of Eu 3+ .…”

Design Principles for 3d Electron Transfer in a Ga-Based Garnet To Enable High-Performance Reversible Thermochromic Material Color Maps

“…However, the new Raman bands may appear in Er 3 Ga 5 O 12 or Er 3 Ga 5– x Cr x O 12 with a small amount of doping, while the intensity of the new bands may too weak to be perceptible. The phenomenon may arise from the lattice tilting and distortion of tetrahedra . With the increase in Mn 3+ doping concentration, the changes in the spectra were obvious, which can be observed in Figure b.…”

“…The phenomenon may arise from the lattice tilting and distortion of tetrahedra. 33 With the increase in Mn 3+ doping concentration, the changes in the spectra were obvious, which can be observed in Figure 6b. The bands between 330 and 420 cm −1 gradually become a wide peak, which may be due to the distortion of GaO 6 and the coupling of the vibration for MnO 6 and GaO 6 with the increase in the amount of Mn 3+ doping.…”

Interpretation of europium(III) spectra

“…can be monitored as a function of pressure [675,676]. Luminescence spectroscopy was used to study the reversible pressure-induced amorphous Eu(OH) 3 [677].…”