Energy transfer from Cr3+ multisites to Tm3+ multisites in yttrium aluminium garnet

Multisite energy transfer from Cr³⁺ to Tm³⁺ was studied using low-temperature high-resolution laser spectroscopy. Selective excitation routes for Tm³⁺ sites were demonstrated using excitation and emission spectroscopy, and were confirmed by lifetime measurements.     

Spectroscopy of multisites Cr3+ and Nd3+ in yttrium aluminium garnet

Cr³⁺ and Nd³⁺ non-equivalent crystal field sites were observed. By use of a high-resolution dye laser,²E and⁴A₂ splittings, zero-phonon⁴A₂ →²E,²T₁,⁴T₂ transitions and vibronic levels of²E doublets of Cr³⁺ non-equivalent centres were recorded. Energy transfers from Cr³⁺ multisites to Nd³⁺ were studied by site-selective spectroscopy and fluorescence decays.     

Family of paramagnetic centers of Ce3+ ions in yttrium aluminum garnet

The electron paramagnetic resonance (EPR) spectra of Ce³⁺ ions in single crystals of yttrium aluminum garnet have been investigated. It has been found that, in addition to the usually observed EPR signals of Ce³⁺ ions located in the regular environment at dodecahedral sites of the crystal lattice, the spectra contain a group of less intense anisotropic lines with g-factors close to the corresponding parameters of Ce³⁺ ions in the regular environment. It has been concluded that the observed satellite lines belong to the family of Ce³⁺ ions in the immediate vicinity of which there are permutation defects that lead to a change in the strength and symmetry of the crystal field in the vicinity of the paramagnetic center.     

Color-center structure in chromium-doped yttrium aluminum garnet

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 48, No. 4, pp. 662–667, April, 1988.     

Paramagnetic resonance of yttrium aluminum garnet doped with 151Eu2+ ions

Physics of the Solid State - The 151Eu2+ orthorhombic centers in yttrium aluminum garnet crystals have been investigated. The initial splitting and hyperfine interaction parameters have been...     

Swift heavy ion irradiation-induced modifications in structural and electrical properties of Y3+-substituted yttrium iron garnet

The consequences of 50 MeV Li³⁺ ion irradiation (fluence: 5×10¹³ ions/cm²) on the structural and electrical properties of the Y_3+xFe_5?xO₁₂ (x=0.0, 0.2, 0.4 and 0.6) garnet system have been investigated over the temperature range of 300–673 K. It is found that the percentage formation of an additional yttrium orthoferrite phase observed along with the bcc garnet phase considerably reduces for x=0.4 and 0.6 compositions after swift heavy ion (SHI) irradiation. The nature of thermal variation of DC resistivity curves for x=0.0 and 0.2 compositions is different from that for x=0.4 and 0.6 compositions. The SHI irradiation influences the magnitude of DC resistivity and conduction mechanism for the single-phase compositions while for mixed-phase compositions they remain unaffected. The results have been explained in the light of replacement of magnetic (5μ_B), smaller (0.64 Å), Fe³⁺ ion by nonmagnetic (0μ_B), larger (0.89 Å), Y³⁺ ion, the presence of the yttrium orthoferrite phase and swift heavy ion irradiation-induced paramagnetic centers in the system.     

Far-infrared spectra of dysprosium doped yttrium aluminum garnet nanopowder

The solution combustion synthesis was used to prepare nanopowders of yttrium aluminum garnet (YAG) and YAG doped with dysprosium ions, Dy³⁺, (YAG:Dy). The morphology, specific surface area, texture, and optical properties of the prepared materials were studied by the means of scanning electron microscopy (SEM), nitrogen adsorption method, and far-infrared spectroscopy at room temperature in the spectral region between 80 and 600 cm⁻¹. It was established that all the examined samples were microporous. The Maxwell–Garnet formula was used to model dielectric function of YAG and YAG:Dy nanopowders as mixtures of homogenous spherical inclusions in air.     

Laser performance of highly neodymium-doped yttrium aluminum garnet crystals

The laser performance of highly neodymium-doped yttrium aluminum garnet (YAG) crystals is reported. In cw laser-diode pumping, a slope efficiency of 54% was achieved for a 2-at. %-doped sample, which was comparable with the slope efficiency of 55% of YVO(4) . The crystal also exhibited a slope efficiency of 64% under pulsed Ti:sapphire pumping. Such a high efficiency suggests a total cavity loss of ~1% , which is as low as that of commercially available 1-at. % YAG crystal. The excellent performance of the neodymium-doped YAG crystals indicates their high optical quality.     

Temperature dependence of the lifetime of Cr3+ luminescence in garnet crystals

The coexistence of sharp R-lines from the ² E state and the broad band from the ⁴ T ₂ state in the photoluminescence spectra of Cr³⁺:Gd₃Sc₂Ga₃O₁₂ (GSGG) and Cr³⁺:Y₃Ga₅O₁₂ (YGG) is observed at low temperature (10K). The decay lifetimes of the broad emission bands of Cr³⁺ in GSGG and YGG are very close to those of the R-lines being, respectively, 0.23 ms and 2.5 ms. These results are explained in terms of the extent of the mixing of the ⁴ T ₂ vibronic wavefunction with that of the ² E lowest excited state by tunnelling.     

Green luminescence and EPR studies on Mn-activated yttrium aluminum garnet phosphor

Yttrium aluminum garnet (Y₃Al₅O₁₂) and Mn activated Y₃Al₅O₁₂ phosphors have been prepared by urea combustion route in less than 5 min. The phosphors are well characterized by powder X-ray diffraction, Scanning electron microscopy and Fourier-transform infrared spectroscopic techniques. Photoluminescence tests on the pure Y₃Al₅O₁₂ showed a strong green emission at 525 nm (2.36 eV) attributed to the strongly allowed transition of F⁺ center whereas in Mn²⁺ activated YAG the green emission at 519 nm is due to the ⁴T₁ (G)→⁶A₁ (S) transition of Mn²⁺ ions. EPR studies have been carried out on Mn²⁺ activated Y₃Al₅O₁₂ phosphor at 300 and 110 K. From EPR spectra the spin-Hamiltonian parameters have been evaluated. The magnitude of the hyperfine splitting (A) indicates that the Mn²⁺ ions are in a moderately ionic environment. The spin concentration (N) and paramagnetic susceptibility (χ) have been evaluated and discussed.