Sínteses e caracterizações de NaNbO3 dopados e co-dopados com Er3+ e Yb3+

Abstract

In this work, we investigated the rare-earth ions concentrations and calcination temperature roles on the structural and luminescent properties of Er3+ and Er3+/Yb3+ doped Sodium Niobate (NaNbO3) nanocrystals. Firstly, the samples were synthesized using the sol-gel Pechinni method. The synthesis route was explained in details using each stage step by step. Following, we investigated the structural properties of the nanocrystals using several techniques: x-ray diffraction was used to characterize the crystalline structure; transmission electron microscopy (TEM) was used to analyze the nanocrystals’ morphology and size; FT-IR and Raman were used to identify structural properties and the possible presence of impurities in the samples. The spectroscopic characterization (luminescence) firstly addressed the energy Upconvesion (UC). Emission spectra in the region from 500 to 700 nm were obtained and identified the main Er3+ emission bands (532, 550, and 667 nm). We also analyzed the energy Downconversion (DC), looking the infrared emission around 1550 nm. All the luminescence measurements were carried out using a cw diode laser at 976 nm. The samples showed a well-defined crystalline single-phase, except the samples calcined at 900oC, which presented a second phase still unidentified. However, we can say we achieved a great success in the synthesis of luminescent nanocrystals by the used method. A strong dependence of the nanocrystals size on the calcination temperature was observed as well as ae decrease of impurities present in the samples (FT-IR). As a result of this reduction of impurities, a strong increase in the emissions was achieved with increasing the calcination temperature. Additionally, higher emissions were obtained for Er3+/Yb3+ co-doped samples. With the doping ions variation, we concluded that the best concentrations, among those studied, for efficient emission in the visible and infrared regions are 5 mol% of Er3+ and 3 mol% of Yb3+. The results obtained in this work indicate that NaNbO3 matrix has potential applications in photonics, in particular applications in bioimaging e nanothermometry.