S.M. Kaczmarek

Changes in Optical Properties of Ce: YAG Crystals under Annealing and Irradiation Processing

Changes of optical properties of cerium doped YAG single crystals (0.05, 0.1, 0.2 at. % Ce, and 0.2 at. % Ce + 0.1 at. % Mg) after thermal annealing at 1400°C in air or 1200°C in N 2 +H 2 mixture and subsequent γ or proton irradiation were investigated. For initial Ce 3+ contents 0,05 at. % a decrease of the final Ce 3+ concentration was observed. Appropriate changes in luminescence of Ce: YAG crystals were observed as a consequence of dopant concentration changes. They were small after γ-irradiation of Ce: YAG crystals with Ce 3+ content >0,05at.% and reached about 100% after γ-irradiation of crystals with Ce 3+ content <0.05 at. %.

Photoacoustic spectroscopy of YAG crystals doped with Ce

Abstract The absorption, luminescence and photoacoustic spectra of YAG:Ce 3+ have been measured and analysed. Considering the photoacoustic and absorption spectra one has shown a decrease of the quantum efficiency of the Ce 3+ below 90% when luminescence is excited in the UV region. Simulation of the kinetics of nonradiative processes in the excited states of Ce 3+ and hot luminescence has been performed. The Jahn–Teller type coupling in the excited states of Ce 3+ has been evidenced.

Growth and Characterization of LiNbO3 Single Crystals Doped with Cu and Fe Ions

Single crystals of lithium niobate doped with 0.03 and 0.1 at.% of Cu or Fe ions were grown by the Czochralski technique. Optical absorption spectra in visible and infrared regions before and after • irradiation with doses up to 10 5 Gy were measured and positions of both dopants in LiNbO 3 lattice were analyzed according to changes in optical absorption in the range of OH group absorption. Some properties of crystals doped with Cu during the growth processes were compared to those for specimens doped by thermodiffusion. It was observed that doping with Cu results in an increase of crystal resistance to radiation.

Radiation Defects in Oxide Compounds

Yttrium-aluminum garnets, strontium and barium lanthanum gallates, lithium niobate and tantalate as-grown crystals and doped by diffusion with rare-earth (Nd, Dy, Er, Tm, Ho, Pr, Ce) and metal transition elements (Mn, Cr) were investigated optically and using Electron Spin Resonance method before and after gamma, electron and proton irradiation.

New cadmium and rare earth metal tungstates with the scheelite type structure

New cadmium and rare earth metal tungstates with the formula Cd0.25RE0.50□0.25WO4 (RE=Nd, Sm, Eu, Gd, □-statistical distributed vacancies in cation sublattice) were synthesized by the solid-state reaction between CdWO4 and corresponding RE2W2O9. The obtained phases crystallize in the scheelite type structure. The Cd0.25RE0.50□0.25WO4 compounds were characterized by X-ray diffractometer (XRD), (DTA-TG), infrared (IR) and EPR methods.

Influence of Ionizing Radiation on Performance of Nd:YAG Lasers

For crystals annealed in oxidizing atmosphere the influence of the dose on the shape of additional absorption spectrum of Nd:YAG samples after gamma and proton (energy of the order of 26 MeV) irradiation’s was described. Changes in optical output of Nd:YAG laser after different value of gamma’s dose were determined. The Nd:YAG crystals were also irradiated with 1 MeV electrons coming from Van de Graaf accelerator. Changes induced in the defect structure of the irradiated crystals were described.

RADIATION INDUCED RECHARGING OF CERIUM IONS IN ND, CE:Y3AL5O12 SINGLE CRYSTALS

Abstract Radiation induced recharging of Ce 3+ and Ce 4+ ions in Ce and Nd doped yttrium-aluminium garnet crystals was observed. This effect depends on the Ce 3+ ion concentration and the type of ionizing radiation. The crystals investigated were irradiated with gamma-rays, protons with fluences up to 10 14 protons/cm 2 and electrons with a fluence of 5 × 10 16 electrons/cm 2 . Changes in cerium concentration after gamma-irradiation were calculated from the formula of Smakula.

Dielectric and magnetic permittivities of three new ceramic tungstates MPr2W2O10 (M = Cd, Co, Mn)

Broadband dielectric spectroscopy measurements revealed an anomalously large relative permittivity value (ε r = 884) for MnPr2W2O10, a smaller value (ε r = 156) for CoPr2W2O10 and the smallest value (ε r = 22) for CdPr2W2O10 at low frequency (ν = 0.1 Hz) and above room temperature in the insulating and paramagnetic state. Below 273 K, the relative permittivity (ε r ∼ 24) did not depend significantly on frequency for all the tungstates under study. Electrical resistivity, thermoelectric power, electron paramagnetic resonance, magnetic susceptibility and magnetization provided experimental evidence that the studies tungstates were paramagnetic insulators with low n-type conduction. Only in the case of MnPr2W2O10 was a ferrimagnetic order below 45 K observed. These effects are discussed within the framework of Maxwell–Wagner polarization, chemical covalent bonds and porosity mechanism.

Effect of ionizing radiation on optical and lasing properties of Y3Al5O12 single crystals doped with Nd, Er, Ho, Tm, Cr ions

Abstract The influence of gamma irradiation on optical and lasing properties of YAG:Er, YAG:CTH, YAG:Nd and YAG:Cr4+ single crystals were studied. For no thermal annealed rods from YAG:Er and YAG:CTH crystals the increase of laser output energy was established. The mechanisms of radiation sensibilization are discussed.

Spectroscopic and magnetic properties of a gadolinium macrobicyclic complex

As a result of Schiff base condensation, gadolinium cryptate has been synthesized and investigated by infrared (IR) spectroscopy and electron paramagnetic resonance (EPR) technique. Comparison of IR bands in a ligand and the gadolinium complex confirmed the formation of the gadolinium cryptate complex. IR and thermogravimetry-differential thermal analysis (TG-DTA) analyses indicate the presence of two water molecules in the inner sphere of the complex. Mass spectroscopy investigations confirmed a monometallic substitution of the Gd3+ ion into the macrobicycle ligand. EPR spectra of the complex have been registered in the 3–300 K temperature range. Each spectrum has been simulated using the EPR–NMR computer program and the values of the spin Hamiltonian parameters at each temperature have been calculated. The thermal dependence of the spin Hamiltonian parameters has been investigated. The temperature dependence of the integrated intensity of the EPR spectrum revealed the magnetic interactions in the spin system of this compound. No long-range magnetic order has been detected in the 3–300 K range, but a strong antiferromagnetic interaction in the high-temperature range, above 160 K, has been observed.