Efeito da concentração de BaF2, BaCl2 e Er2O3 nas propriedades estruturais, ópticas e espectroscópicas de vidros borato de bário

Abstract

In this work we performed the synthesis and structural, optical and spectroscopy characterization of barium borate glasses with composition (100 – z)[B2O3 + (40 – x – y)BaO + xBaF2 + yBaCl2] + zEr2O3, where x and y = 0.0, 2.5 and 5.0 mol%, besides z = 0.0, 0.5 and 1.0 mol% of Er2O3. Density measurements were performed through Archimedes’ principle and refractive index using Brewster angle technique. We verified an increasing in the density and refractive index values with increasing rare earth (RE) concentration. The values of density and refractive index also increase with BaF2 increment and present inverse trend when BaCl2 increases. We used Raman and Infrared technics to identify different vibrational groups present in the studied samples. The analysis indicated the conversion of BO4 into BO3 units, which implies on arising of non-bridging oxygens (NBOs) in the glass structure. Optical absorption measurements were performed and using obtained data, we calculated Judd-Ofelt (JO) parameters (Ωt, com t = 2, 4 e 6). We observed a greater variation of Ω2 values than Ω4 and Ω6 values, when Er2O3 content increases, this is associated to the great asymmetry surrounding Er3+ ions. In relation to the BaF2 increment, there is an increasing followed by a reduction of Ω4 and Ω6 values. An opposite behavior is observed for BaCl2 increment. The optical absorption measurements were also used to calculate the optical band gap for direct and indirect transitions, besides Urbach energy whose results also suggest conversion of BO4 into BO3 units and appearance of NOBs. Exciting the samples at 379 nm we verified the emission in the infrared region, at 1550 nm, for 4𝐼13⁄2 → 4𝐼15⁄2 transition. We observed higher emission for samples containing 0.5 mol% of Er2O3 than for samples containing 1.0 mol% of Er2O3 concentration. This was associated to the energy process transfers between Er3+ ions and multiphonon relaxation. The decay lifetime of 4𝐼13⁄2 level was monitored for the studied samples. For majority of samples the lifetime decay increases when halides and Er2O3 were added, in comparison to the samples with non-halide samples. This is related to decreasing of high phonon energy provoked for the halide’s insertion. Radiative parameters were calculated using Judd Ofelt parameters, characterizing in turn the applicability of studied glassy samples. We concluded that the BBOEr0.5 glass sample is the most suitable for optical amplifiers.