Nd 3+:YAG–Al 2O 3 nanocrystalline transparent ceramics with high inflexion concentration quenching of Nd 3+ prepared by amorphous crystallization

Rare earth ions doped YAG-based transparent ceramics have acted as important laser gain medium for a long time, yet the doping concentration of active ions is limited due to concentration quenching wherein the inflexion concentration quenching of Nd³⁺ is recognized as 1.0 at%. In this work, YAG-Al₂O₃ nanocrystalline transparent ceramics with the concentration of Nd³⁺(0~5.0 at%) have been fabricated via amorphous crystallization, and the crystal structure evolution, the morphology and the optical properties were systematically investigated by DSC, XRD, TEM, MAS NMR and fluorescence spectra. The doping of Nd³⁺ can promote the transition of Al^[5] and Al^[6] to Al^[4], indicating the improvements of the amorphous formation ability to gain Nd³⁺:Y₂O₃-Al₂O₃ vitrify beads, and 1.5 at% Nd³⁺:YAG-Al₂O₃ nanocrystalline transparent ceramics can be obtained by crystallized at 1050°C with the matrix compositing of YAG and concomitant δ-Al₂O₃ and θ-Al₂O₃. The nanocrystalline transparent ceramics show the internal transmittance of 89.56% at 1064 nm, and the strongest emission peak corresponding to the energy transfer from ⁴F_3/2 to ⁴I_11/2 of Nd³⁺ with the fluorescence lifetime of 231 μs pumped by 808 nm laser. Specially, spectral broadening begins to occur, indicating the onset of concentration quenching, when the concentration of Nd³⁺ exceeds 1.5 at%, substantially higher than 1.0 at% observed in YAG ceramics. YAG-Al₂O₃ nanocrystalline transparent ceramics obtained by amorphous crystallization can be utilized as the matrix to increase the inflexion point of doping concentration quenching of Nd³⁺, and this material may have great potential as laser gain medium.