Anomalous discrete disorder response of high-symmetry impurity centers spectra in garnet solid solutions

Abstract

The zero-phonon electronic transitions in Cr(3+) and Ce(3+) impurity ions in a series of Lu3xY3-3xAl5O12 (0 < x < 1) garnet solid solution crystals were studied experimentally. It was observed that in contrast to the case of Ce(3+), the modification of zero-phonon R-line ((2)E-(4)A2) fluorescence spectra of Cr(3+) ions with changing x occurs in a discrete fashion and is not accompanied by strong inhomogeneous broadening, as usually happens in solid solutions. The effect is ascribed to the high C3i symmetry of the Cr(3+)(Al(3+)) sites that allows only a limited number of non-equivalent Cr(3+) centers in a mixed environment. The energies and radiative lifetimes of the (2)E states of locally identical Cr(3+) centers inside different mixed garnet matrices were studied and the observed dependences on the Lu content x are discussed in terms of lattice compression and dilation.

Disorder response of 3d3 ions zero-phonon lines in the luminescence spectra of Yttrium-Aluminum-Gallium garnet solid solution ceramics

“…The behavior of the Cr 3+ spectra in Y 3 Al 5-5y Ga 5y O 12 samples with the change of y at its lower values is similar to that reported in [3] for Lu 3x Y 3-3x Al 5 O 12 : a discrete structure is observed when the smaller aluminum ions are one by one replaced with larger gallium ones. At T = 10 K the luminescence lines correspond mostly to the lower-energy (R 1 ) components of the doublet 2 E-4 A 2 transitions, though some contribution of partially occupied higher-energy (R 2 ) transition is still present, at T = 77 K the contribution of R 2 transitions becomes more significant due to increased thermal (Boltzmann) population.…”

“…At high values of y the behavior of the Cr 3+ spectra in Y 3 Al 5-5y Ga 5y O 12 samples with the change of y is different from the discrete spectra observed at (y=0.2) and from the discrete spectra of the Lu 3x Y 3-3x Al 5 O 12 series [3]. The strong inhomogeneous broadening of the R-lines occurs and no discrete disorder response is observed.…”

“…In our previous studies it was observed [3,4] that (in contrast to most studied materials) the modification of zero-phonon R-lines ( 2 E- 4 A 2 ) in the luminescence spectra of Cr 3+ impurity ions in the concentration series of Lu 3x Y 3-3x Al 5 O 12 (0 ≤x≤1) and Tb 3z Y 3-3z Al 5 O 12 (0 ≤z≤1) garnet crystals occurs in a discrete rather than a continuous fashion and is not accompanied by strong inhomogeneous broadening. The effect was ascribed to high C 3i symmetry of octahedral Cr The purpose of the study presented here is to trace the modification of the zero-phonon R-line spectrum of garnet solid solutions in a more complicated situation of the disorder introduced into the sublattices of tetrahedral and octahedral Al/Ga sites.…”

“…In [3] the discrete modification of R-line spectra of Cr 3+ in LuYAG crystals with the change of Lu/Y ratio was explained by the high symmetry of Cr 3+ center in the crystal lattice. In the cubic O h garnet lattice Cr 3+ ions replace the Al 3+ ions in the octahedral sites of a C 3i symmetry and are surrounded by six oxygen ions [6,7].…”

Nanoengineered Gd3Al2Ga3O12 Scintillation Materials with Disordered Garnet Structure for Novel Detectors of Ionizing Radiation

“…Broadening of the 4f–4f transitions evidently confirms that even a random distribution of cations in the lattice results in considerable distortion of the lattice. The distortion results in several different spatially nonequivalent positions in the garnet‐type lattice for the localization of trivalent iron group and rare‐earth dopant ions …”