Yttrium Gallium Garnet Research Articles

Aqueous Sol-Gel Synthesis Methods for the Preparation of Garnet Crystal Structure Compounds

In the present review, the usefulness of aqueous sol-gel processes in the synthesis of garnet crystal structure compounds is discussed. The processing and characterization of yttrium aluminium garnet (YAG), lanthanide-doped YAG, lanthanide aluminium and gallium garnet materials, mixed-metal garnets and garnets containing silicon are described. The synthesis of garnet materials comprising nanoscale architectures is also discussed.http://dx.doi.org/10.5755/j01.ms.17.4.782

Nd:YGG crystal laser at 1110 nm: a potential source for detecting carbon monoxide poisoning

We demonstrated a laser-diode pumped Nd-doped yttrium gallium garnet crystal laser at 1110 nm for the first time to our knowledge. By suppressing the oscillation at about 1.06 μm, continuous-wave output power of 2.1 W at 1110 nm was achieved. With a Cr:YAG as the saturable absorber, the passive Q-switching performance at this wavelength was obtained. The shortest pulse width and largest pulse energy were 31.5 ns and 22.7 μJ, respectively. Laser radiation at this wavelength is an important source for detecting carbon monoxide poisoning by simple frequency doubling with a nonlinear crystal.

Efficient triwavelength laser with a Nd:YGG garnet crystal

We demonstrate a laser-diode pumped efficient triwavelength laser at about 1.06microm with a Nd-doped yttrium gallium garnet crystal for the first time, to our knowledge. Continuous wave output power of 7.15W was achieved under an absorbed pump power of 14.1W, corresponding to the slope efficiency of 52.7%. With Cr:YAG as the saturable absorber, passive Q-switching performance was obtained. The shortest pulse width, largest pulse energy, and highest peak power were obtained at 3.1ns, 153.8microJ, and 46.6kW, respectively. The laser spectrum was found to be a triwavelength, with respective wavelengths of 1062.1, 1060.3, and 1058.9nm, and three laser transitions were assigned.

Theoretical study on local defect structure of (FeO4)5− clusters in YGG and LGG crystals

The optical spectrum and the local defect structure of tetrahedral (FeO4)5− clusters are investigated in yttrium gallium garnet (YGG) and lutetium gallium garnet (LGG) crystals by means of the 252×252 complete energy matrices for d5 configuration ions in tetragonal ligand field. The results show that the local defect structures around tetrahedral Fe3+ centers display an expansion effect. Simultaneously, the (FeO4)5− clusters in the two different crystals have very similar local structures, which are close to those in YIG garnet crystal. Finally the relative curves of the zero-field splitting energies ΔE1 and ΔE2 in the ground state 6A1 varying with the structure parameter θ are plotted.

Local defect structures and EPR studies on (FeO6)9− and (FeO4)5− clusters in YGG: Fe3+ system

The octahedral (FeO6)9− and tetrahedral (FeO4)5− clusters in yttrium gallium garnet (YGG): Fe3+ system are investigated based on the 252 × 252 complete energy matrices for d5 configuration ions in trigonal and tetragonal ligand fields, moreover, the EPR and optical spectra are made unified calculation. The results indicate that the defect structures around Fe3+ centres display expansion effects at different temperatures 4.2 and 295 K, and which are close to those in YIG garnet, respectively. Simultaneously, the defect structure parameters for Fe3+ centres in YGG are determined, and the relationship between the defect structure and the temperature has been discussed.

Structure–property correlations in Ce-doped garnet phosphors for use in solid state lighting

The discovery of inorganic phosphors that can be excited by GaN light emitting diodes in the wavelength range 380–460 nm is essential for improving the efficiency and light quality of solid state lighting devices. Garnets doped with Ce 3+ are of particular interest for this application. We have studied the luminescence of Ce 3+ in garnet phosphors and established a relationship between the excitation/emission wavelengths and the deviation from cubic symmetry around the rare-earth ion. Data are presented for both known yttrium aluminum and yttrium gallium garnet systems, as well as newly synthesized inverse garnets of the general formula Mg 3Y 2− y Gd y Ge 3− z Si z O 12:Ce (0 ⩽ y ⩽ 2, z = 0, 1).

Preparation and characterization of yttrium gallium garnet nanoparticles by citrate sol–gel method at low temperature

The Y 3Ga 5O 12 (YGG) nanoparticles with pure phase have been successfully prepared with Y(NO 3) 3 and Ga 2O 3 at lower sintering temperature and shorter holding time. The process of citrate sol–gel method was simple and the cost was very low. The thermal behavior of the YGG precursor was characterized by thermogravimetry/differential thermal analysis (TG/DTA). The crystallization temperature was determined by X-ray powder diffraction (XRPD). The morphology of the particles was characterized by transmission electron microscope (TEM). The results illustrate that the crystallization temperature of YGG nanoparticles was about 700 °C and the powders made by this method dispersed uniformly.

EPR theoretical study of local lattice structure of Fe 3+ in octahedral site in yttrium gallium garnet

By analyzing the EPR parameters D and ( a− F) of Fe 3+ ion located at octahedral site in yttrium gallium garnet, the local lattice structure around Fe 3+ ion in the crystal has been investigated on the basis of the complete energy matrices for a d 5 configuration ion in a trigonal ligand field. It is shown that there exists a slight expansion distortion in the local lattice structure and the distortion is different at 4.2 and 295 K. This result may be attributed to the fact that the radius of Fe 3+ ion is larger than that of Ga 3+ ion, and the Fe 3+ ion will push the two oxygen triangles to move upwards and downwards, respectively, along C 3-axis when the temperature decreases. From EPR calculation, the local lattice structure parameters R = 2.0068 Å, θ = 51.4691 ° at 295 K and R = 2.010 Å, θ = 51.3706 ° at 4.2 K for octahedral Fe 3+ centre in yttrium gallium garnet are determined.

Low-temperature synthesis and characterization of yttrium–gallium garnet Y 3Ga 5O 12 (YGG)

To obtain yttrium–gallium garnet (Y 3Ga 5O 12, YGG) a simple “chimie douce” method has been developed. This sol–gel method yielded excellent starting gel precursor for the fabrication of YGG phase, which could be used as host material for optical applications. The pattern of X-ray diffraction analysis of the ceramic sample sintered for 10 h at 1000 °C showed the formation of monophasic Y 3Ga 5O 12 phase. The phase transformations, composition and micro-structural features in the gels and polycrystalline sample were studied by thermoanalytical methods (TGA/DTA), powder X-ray diffraction analysis (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The quality of the resulting products (homogeneity, crystallisation temperature, grain size, grain size distribution, etc.) is discussed.

Attribution of the absorption bands of ruthenium-doped yttrium gallium garnet crystals to Ru3+, Ru4+, and Ru5+ 4d-ions by MCD

Abstract Ruthenium-doped yttrium gallium garnet single crystals were grown from a PbO/PbF2/B2O3 flux. Most samples are blue, occasionally green, orange or lemon yellow, depending upon the growth temperature and the amount of a divalent or tetravalent counterion. A spectroscopic study was carried out using several complementary techniques (optical absorption, MCD, and EPR). Low temperature MCD enabled discrimination among those absorption bands correlated to paramagnetic ions (Ru3+ or Ru5+) or diamagnetic Ru4+ at the octahedral site. Ru3+ dominates in the lemon yellow sample with a nominal Ge/Ru ratio of ≈7, whereas Ru5+ is responsible for the orange colour in a crystal with Ca/Ru ≈7. The strongest MCD features above 2.2 eV could be rationalised in terms of oxygen-to-Run+ (n = 3–5) charge transfer transitions in octahedral complexes, whereas the 2 eV band of blue crystals is tentatively assigned to an intervalence transition implying Ru4+. It is suggested that YIG films co-doped with ruthenium and a large amount of calcium or germanium might present interesting Faraday effect properties.

X-ray and optical studies of ytterbium-doped gallium garnets

Single crystals of yttrium gallium and lutetium gallium garnets doped with ytterbium were grown from the melt by Czochralski technique. Comparison is made between the lattice spacing of ceramic and single crystals to estimate the degree of octahedral ytterbium substitution. When heated to around 1200°C under reducing atmosphere the yttrium gallium garnet crystal acquires violet color due to appearance of additional absorption bands. Displacements of absorption bands as a function of the average radius on the dodecahedral site resemble those observed in aluminum garnets and generally considered as associated with divalent ytterbium. Basing on X-ray calibration, the peak positions of induced absorption bands can be used to estimate the dodecahedral concentration of ytterbium in the crystal. Charge transfer luminescence properties were studied in LuGG:Yb crystals.

Crystal growth of Yb 3+-doped oxide single crystals for scintillator application

Long emission wavelength scintillators are strongly required from the viewpoint of the practical use of silicon photo-diode, which has higher resolution with lower cost compared with photo-multipllier. Among the various scintillator emission centers, we regard emission from Yb 3+ charge-transitions state (CTS) as a candidate. In order to investigate proper hosts for Yb 3+ CTS, the yttrium gallium garnet host and lutetium aluminum garnet host were studied. Transparent and crack-free heavily Yb-doped YGG, i.e. {Y 1− x Yb x } 3[Ga] 2(Ga) 3O 12 (Yb: YGG, x=0.15, 0.5, 1.0) and heavily Yb-doped LuAG, i.e. {Lu 1− x Yb x } 3[Al] 2(Al) 3O 12 (Yb: LuAG, x=0.15, 0.5, 1.0) single crystals could be grown by the Modified Pulling Down method with 〈1 1 1〉 orientation. Emission, excitation spectra and decay kinetics were measured for these crystals. The CT transition of Yb 3+ in the yttrium gallium garnet host was discussed compared with the Yb 3+ one in the lutetium aluminum garnet host.

Evaluation of the parameters of cation distribution in Y3A5−z B z O12 solid solutions

Crystal chemical models are proposed for describing the regularities in the distributions of ions and point defects in solid solutions of yttrium aluminum, yttrium gallium, and yttrium iron garnets. The concentration dependences of the distributions of ions and point defects in solid solutions are evaluated in terms of multidimensional nonlinear optimization.

Spectroscopy and Continuous Wave Near-Infrared Stimulated Emission of New Yttrium Gallium Garnet {Y3}[Y, Ga](Ga3)O12:Nd3+ (YGaO3:Nd3+)

Detailed spectroscopic investigations are made for a new laser material, a Nd3+-ion doped YGaO3 garnet crystal with disordered structure, grown from the physicochemical Y2O3-Ga2O3 system with sesquioxide relation close to 1:1. Following absorption and luminescence spectral analyses, the Stark splitting of the 4F3/2 and 4Ij’ manifolds of Nd3+ activators are measured with high accuracy. Between the Stark levels of two near-infrared laser channels (4F3/2→4I11/2 and 4F3/2→4I13/2) low-threshold continuous wave stimulated emission was excited at 300 K. Some spectroscopic characteristics, such as radiative lifetime of the initial laser 4F3/2 state, intermanifold and inter-Stark luminescence branching ratios, linewidths, spontaneous transition probabilities and peak and effective cross-sections of induced transitions are also determined. These parameters are necessary for a theoretical description of the functional properties of Nd3+:YGaO3 lasers.

Selectively excited luminescence and magnetic circular dichroism ofCr4+-doped YAG and YGG

Site selective luminescence and magnetic circular dichroism experiments on ${\mathrm{Cr}}^{4+}$-doped yttrium aluminum garnet and yttrium gallium garnet have been made at low temperature. The spectral assignments for these near-IR lasing materials have been made using experimental data and ligand field calculations guided by the known geometry of the lattices.

Temperature dependent EXAFS measurements on YGG during a sol-gel process

Temperature dependent X-ray absorption spectroscopy has been used as a local probe to elucidate the structure of yttrium gallium garnet produced by a sol-gel route. The treatment of our experimental data includes a cumulant expansion analysis taking into account the asymmetry of the pair distribution function resulting from disorder at high temperature.

Infrared spectroscopy of yttrium aluminum, yttrium gallium, and yttrium iron garnets

All 17 infrared lattice modes for yttrium aluminum, yttrium gallium, and yttrium iron garnets Y3R2(RO4)3 are obtained from single-crystal reflection and absorption spectroscopy, and the powder technique. Assignments for 12 modes are firmly establish based on chemical substitution among these garnets and within related series. Frequencies of the modes associated with translation of yttrium are nearly constant across the series. Frequencies of all other modes decrease quasilinearly as cell volume increases. Values the high and low frequency dielectric constants are in good agreement with independent measurements; also, the Lyddane–Sachs–Teller relationship was found to hold. Calculations of bulk moduli from vibrational spectra using a modification of Brout’s formula linearly correlate with experimental values for KT.

Crystal-field theory and the S-state splitting of Fe3+ in yttrium gallium garnet.

Calculating the S-state splitting of a ${\mathit{d}}^{5}$ ion (${\mathrm{Fe}}^{3+}$, ${\mathrm{Mn}}^{2+}$) in a crystal has been a long-standing difficult problem since 1934 when it was discussed by Van Vleck and Penney. Low and Rosengarten have concluded that crystal-field theory is not capable of providing a unified interpretation for the spectrum and for the S-state zero-field splitting of ${\mathit{d}}^{5}$ $^{6}$S ions. In the present paper, by utilizing a method of combined perturbation composed of the electrostatic, crystal-field, and spin-orbit-coupling energies, and by diagonalizing a set of complete energy matrices constructed for a ${\mathit{d}}^{5}$ configuration and having a total order of 252, a reasonable interpretation is obtained for the d-d spectrum and the EPR cubic zero-field splitting of ${\mathrm{Fe}}^{3+}$ ions located at octahedral and tetrahedral sites in yttrium gallium garnet. This shows that crystal-field theory is as well suited for application to ${\mathit{d}}^{5}$ ions and to other ${\mathit{d}}^{\mathit{n}}$ ions and that the earlier Low-Rosengarten conclusion is wrong. It is also shown that contributions to the ground-state splitting arising from various excited states of the ${\mathit{d}}^{5}$ configuration or from various components of the crystal field do not obey a linear-superposition rule. In the Appendix, a detailed explicit description of the matrices is given.

Continuous wave 1.6 ?m laser action in Er doped garnets at room temperature?

We report on room-temperature cw laser action of Er3+: Yttrium-aluminum-garnet (YAG) and Er3+: Yttrium-gallium-garnet (YGG) crystals at 1.64 μm. The laser operates from the metastable4I13/2 manifold into an upper Stark level of the4I15/2 ground-state manifold of Er3+. Due to reabsorption losses, the Er3+ concentration of the laser crystals must be low. Laser pumping at a wavelength of 647.1 nm yields lowest thresholds around 30 mW and slope efficiencies up to 12.7% for Er:YAG. Laser operation in Er:YGG is achieved with higher thresholds of about 200 mW and smaller slope efficiencies of 0.9%. The effective emission cross section in YAG is estimated to be σe≈5×10−21 cm2.

TRANSFER CHARACTERISTICS OF NONRADIATIVE ENERGY FROM Tb3+ TO Ce3+ IN YTTRIUM GALLIUM GARNETS

Selection-excited spectra and fluorescence lifetimes of Tb3+ and Ce3+ ions in yttrium gallium garnets are obtained at room temperature. In Y3Ga5O12:Tb, Ce, Tb3+ (donor) emission spectrum and Ce3+( acceptor) excitation spectrum overlaps considerably. The observed fluorescence lifetimes of Tb3+ 5D3 and 5D4 levels decrease with Ce3+ concentration when the sample of Y3Ga5O12: Tb, Ce are excited by UV laser pulse. The mechanisms for nonradiative energy transfer from 5D3 and 5D4 states of Tb3+ to 2D3/2 state of Ce3+ are found to be electric dipole-dipole interaction. The critical distance, rate and efficiency of energy transfer from Tb3+ to Ce3+ ion are obtained. The average critical transfer distance (R0) for 5D3 and 5D4(Tb3+)→2D3/2(Ce3+) are 16.3 ? and 11.2 ?, respectively. Although the energy transfer from the 5D4 state is dominated by dipole-dipole interaction, the dipole-quadrupole interaction must also be considered.