Effect of Temperature and High Pressure on Luminescence Properties of Mn³⁺ Ions in Ca₃Ga₂Ge₃O₁₂ Single Crystals

Abstract

In this work, the temperature and high-pressure behaviors of Mn 3+ -doped garnet-type Ca 3 Ga 2 Ge 3 O 12 single crystals have been investigated by means of photoluminescence and Raman spectroscopy, respectively. The Jahn−Teller stabilization energy in the 5 E ground state was found to be 1630 cm −1 , being as much as 6 times greater than that in the 5 T 2 excited state, that is, 237 cm −1 . The room-temperature emission spectrum is dominated by the spin-allowed 5 T 2 → 5 E transition at 670 nm upon 532 nm excitation. The temperature dependences of photoluminescence spectra and time decays reveal strong thermalization between 5 T 2 and 1 T 2 levels. Cooling to 50 K empties the 5 T 2 level by virtue of multiphonon transition to the lower-lying 1 T 2 level. As a result, the 1 T 2 → 3 T 1 / 5 E electric-dipole transitions are induced by coupling to odd-parity phonons. The existence of a small amount of Mn 4+ can be ascertained by lowering the temperature or applying high pressure. Upon compression up to 100 kbar, the 5 T 2 → 5 E transition of Mn 3+ undergoes a blue shift at a rate of ∼10.5 cm −1 /kbar. Since both 5 T 2 and 1 T 2 have inverse crystal field dependences, the quenching process from the 5 T 2 level becomes stronger under high pressure. Cryogenic luminescence ratiometric thermometry based on the diverse thermal quenching behaviors of Mn 3+ and Mn 4+ was explored. Furthermore, theoretical calculations employing the exchange-charge model of crystal field for Mn 3+ and Mn 4+ ions in Ga 3+ octahedral sites (C 3i ) in garnet-type Ca 3 Ga 2 Ge 3 O 12 remain in perfect agreement with the experimental data.

Multiple-Valence and Visible to Near-Infrared Photoluminescence of Manganese in ZnGa2O4: A First-Principles Study

“…It should be noted that the electronic repulsion B of Mn 3+ is larger than that of Mn 4+ , which shows the larger nephelauxetic effects of Mn 4+ than Mn 3+ (i.e., much more delocalization of 3d orbitals of Mn 4+ into the ligands than that of Mn 3+ ). Similar results have been reported previously . Experimentally, a reasonable estimation of the ligand-field strength for the Tanabe–Sugano model is to subtract half of the JT split from the excitation energy, and the ligand field strength is estimated as 2.23 eV from experimental data, , in agreement with our DFT results.…”

“…Similar results have been reported previously . Experimentally, a reasonable estimation of the ligand-field strength for the Tanabe–Sugano model is to subtract half of the JT split from the excitation energy, and the ligand field strength is estimated as 2.23 eV from experimental data, , in agreement with our DFT results.…”

“…However, the luminescence of Mn 3+ is usually ignored, and Mn 3+ is considered as a quenching center of the luminescence . The NIR luminescence in ZnGa 2 O 4 /Mn has been observed recently, and the unique temperature-dependent red even NIR emission of Mn 3+ is studied experimentally in garnet hosts. , Here, the luminescence properties of rarely reported Mn 3+ are studied in detail by first-principles calculations.…”

“…Recently, the green, red, and near-infrared (NIR) emissions are reported in halide perovskites, and an energy-transfer route from the host to dopants leads to high-efficiency Mn 2+ luminescence . Mn 3+ provides a red to NIR emission and appears to be an interesting candidate for an active laser center . The luminescence of Mn 3+ has been studied experimentally in garnets, but systematic theoretical and first-principles computational studies on the JT effect and the luminescence properties of Mn 3+ are still lacking.…”

Tuning Multicolor Emission of Manganese-Activated Gallogermanate Nanophosphors by Regulating Mn Ions Occupying Sites for Multiple Anti-Counterfeiting Application

“…01-071-0843) with an Fd3m space group and rhombohedral Zn 2 GeO 4 (JCPDS No. 04-007-5691) with an R3 space group [6,14,15]. While the XRD patterns of Zn 2.…”