Estudos espectroscópicos de vidros sódio aluminofosfatos co-dopados com Yb3+ e Tm3+ [thesis]

Idelma Aparecida Alves Terra
This work presents a throughout near-infrared and visible spectroscopic characterization of two sets of Yb 3+ and Tm 3+ codoped sodium aluminophosphate glasses, prepared in nitrogen and ambient atmospheres. In these samples, the Yb 3+ ions are employed as efficient sensitizers of 0.98 µm excitation, with subsequent energy transfer to Tm 3+ ions. Results are discussed in terms of the inferred OHcontent in each set of samples, and as a function of Tm 2 O 3 concentration. Radiative properties are
more » ... ive properties are analyzed using Judd Ofelt theory, and by employing experimental and theoretical data, the fluorescence quantum efficiencies η of several levels are evaluated. Results indicate that samples prepared in N 2 atmosphere, with lower OHcontent, present superior properties than those prepared in ambient atmosphere. Among these properties are a 30% more extensive infrared transmission of the host matrix, higher emission intensities, and decreased quenching effects, characterizing them as potential materials for high power laser generation, as well as efficient upconversion. Also the energy transfer processes were studied, by using Förster, Dexter and Miyakawa theoretical models, the energy transfer parameters were calculated. The main ion-ion energy transfer processes analyzed were: energy migration among Yb 3+ ions, energy transfer between Yb 3+ and Tm 3+ ions, and interactions with OHradicals.The results indicated that Yb→Tm energy transfer favors 1.8 m emission, and there is no evidence of concentration quenching up to 2% Tm 2 O 3 doping. % O termo terras-raras se deve, a tardia descoberta no final do século XVIII, de novos e incomuns minérios e às dificuldades iniciais na sua separação. A partir destes novos minérios outros foram sendo isolados dando origem a vários elementos. [15] % & ( ( J J A J J A J J A dm de T A razão de ramificação é dada por: Na figura 4.6 (A) são mostradas as curvas de decaimento temporal em escala semilogaritímica da população do nível 3 F 4 , para as amostras processadas em atmosfera ambiente. Onde observamos uma dependência temporal exponencial, nas curvas de decaimento temporal da luminescencia do referido nível, para as várias concentrações de Tm 3+ em nossas amostras. A figura 4.6 (B) apresenta a comparação do decaimento temporal do nivel 3 F 4 para as amostras menos concentradas (0.1%Tm 3+ ), obtidas nas duas condições atmosferas (atmosfera ambiente e de nitrogênio). % & D $ . % D % .
doi:10.11606/d.88.2007.tde-21112007-132715 fatcat:46oowmbzfncv5b7ea6sxigjbxm