Incorporação de prata em vidros germanatos e teluritos contendo óxido de tântalo

Abstract

The purpose of this study was the preparation of germanate and tellurite glass containing tantalum oxide and the incorporation of silver on its matrixes, aiming at the characterization of the silver’s influence on the optical properties and on the crystallization mechanisms of the materials as well. The systems used for the glass’s preparation were (70-x)GeO2 – 10K2O – 20Ta2O5 – xAgNO3 e (80-x)TeO2 – 20(0,5Ta2O5) – xAgNO3, where x represents the silver nitrate proportion that was used (%mol). The pieces obtained appeared homogenous and yellowish for both systems. The use of the exploratory calorimetry through DSC technique allowed the characteristic temperature’s determination (Glass transition temperature, crystallization onset temperature and crystallization temperature) and showed that the incorporation of silver in the matrix favors the formation of the crystalline phase at lower temperatures. Thermal treatments at predefined temperatures were performed to evaluate the possibility of silver precipitation in the matrix, as well the crystallization of oxide phases. The results obtained do not allow to affirm that silver precipitation has occurred in any of the vitreous systems. However, promising results were obtained for the Ge-05Ag sample, allowing to say that the composition used has high potential for precipitation of NPs. Regarding glass tellurites, the homogeneous darkening after the samples thermal treatment may be related to the presence of precipitated Ag nanoparticles in the matrix, even with larger than expected sizes. The DRX analysis showed that there was no influence of silver on the material crystallization process.