The crystal structure of the EGG garnet, (a) shows one crystal unit cell, and (b) depicts part of the unit cell in which the Eu3+ ion lies between the octahedra and tetrahedra. In the cubic structure, Ga1 3+ occupies the octahedral site at the (0, 0, 0) position, Ga2 3+ occupies the tetrahedral site with (3/8, 0, 1/4) coordinate, and Eu3+ is at the dodecahedral site with the (1/8, 0, 1/4) coordinate, respectively. Oxygen has the general coordinate (x, y, z).
Representative x-ray diffraction pattern of Eu3Ga5O12 (EGG) with the Rietveld refinement at ambient conditions.
Representative angle-dispersive x-ray diffraction patterns (wavelength λ = 0.6199 Å) of EGG at high pressures. The patterns above 50 GPa were collected in the first run mixed with Pt, while the spectra below 50 GPa were collected in the second run without Pt.
Comparison of the x-ray diffraction patterns before and after laser-heating the EGG garnet. The bottom spectrum represents the x-ray diffraction of the cubic garnet phase, and the top shows the high-pressure orthorhombic phase after laser-heating.
Experimental P-V data of EGG. The inset is pressure dependence of the distances between nearest polyhedra (dodecahedra, octahedra, and tetrahedra).
Characteristic fluorescence spectra for the 5D0 → 7F J (J = 1, 2) transition of Eu3+ in Eu3Ga5O12 at high pressures. The sharp peak at 16385 cm−1 marked with * represents the laser line.
Luminescence intensity ratio I 2/1 of the I(5D0 → 7F2) to I(5D0 → 7F1) transitions as a function of pressure.
Pressure evolution of (a) the Raman spectra of EGG and (b) the corresponding frequencies.
Experimental conditions. Room temperature: RT; Photoluminescence: PL.
Derived vibrational parameters of Eu3Ga5O12 from high-pressure Raman results. ω0 : Raman frequency at ambient pressure; dωi/dP: pressure derivative of the Raman frequency; γi: mode Grüneisen parameter.
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