Vidros e vitrocerâmicas no sistema binário NaPO3 – Ta2O5

Abstract

The goal of this present work was to synthesize and characterize vitreous samples based on sodium phosphate (NaPO3) and tantalum oxide (Ta2O5). It is known that these materials present the hability to form a hosting matriz for rare earth ions, making them interesting for applications in the field of optics. The objective was to understand the parameters of temperature that could lead to the precipitation of tantalum oxide nanocrystals in a glassy matrix and the influence of this structure on the modifications of the properties luminescent material. Studies for the determination of the vitreous domain of the composition were carried out by preparing samples with increasing molar content of tantalum oxide. Vitreous samples were obtained by the melt-quenching technique for the composition (100 − x)NaPO3 − xTa2O5 where the x value was in a range between 10 to 50% in molar fraction. Thermal analysis measurements were performed by DSC, to determine the glass transition temperatures and crystallization peaks. These analyzes exhibited the dependence of the glass transition temperature as a function of the amount of tantalum oxide present, reaching the value of Tg = 920◦C for the sample containing 50% of Ta2O5 . A stable sample was obtained for this concentration, a fact that deserves to be highlighted due to the lack of information on obtaining stable bulk samples by the melt-quenching with these amount of tantalum oxide. Parameters for thermal treatment wer defined and a glass-ceramic was obtained. X-ray diffraction analysis confirmed the vitreous structure of the samples and also confirmed the precipitation of tantalum content crystalline phase e Na2Ta8O21 for the glass-ceramic obtained. FTIR and Raman spectroscopy analyzes showed the structural evolution of the glasses as a function of the increase of the molar fraction of tantalum oxide. UV-Vis absorption analyzes showed good transparency of the samples and allowed to verify the decrease of bandgap as the Ta 2 O 5 concentration increases. The incorporation of tantalum oxide promotes a significant increase in the connectivity of the vitreous network due to the insertion of oxide polyhedra in the chains and thus contributing to a more rigid glass network with high chemical and thermal stability.