Vidros dopados e co-dopados com Yb3+, Er3+ e Nd3+ para termometria óptica

Abstract

The optical thermometry based on thermally coupled levels has proven to be an advantageous technique when compared to the use of thermal contact sensors, which undergo strong interference from electromagnetic fields, as well as pyrometers, which show a strong depend-ence on the emissivity of the body under analysis. In this context, the current dissertation stud-ied the performance of three glasses doped with ytterbium, erbium, and neodymium as thermal sensors through the luminescence intensity ratio (LIR) technique. The glass samples were char-acterized by temperature-dependent fluorescence spectroscopy, x-ray diffractometry, UV-Vis absorption spectroscopy, and transmission electron microscopy. In Er3+/ Ag nanoparticles cod-oped zinc telluride glasses, we confirmed the presence of Ag nanoparticles with an average size of 12 nm ± 4 nm that contributed to a significant increase in emissions in the entire visible spectrum at a concentration of 1% mol of AgCl. The increase in the local field and the transfer of non-radiative energy between Ag NPs and Er3+ are the main reasons for the increase in lu-minescence. In this case, the presence of Ag NPs enhanced the maximum of absolute sensitivity from 1.9410-3 K-1 (Ag-free) to 2.7910-3 K-1 (1% mol AgCl) at 446 K. In Er3+/Yb3+- codoped tungsten sodium phosphate glass, the increase in the PbF2 concentration raised the relative sen-sitivity (SR) from 779.2/T2 (10% mol PbF2) to 1053.4/T2 (50% mol PbF2). Furthermore, more PbF2 led to a continuous increase in SA in the studied temperature range. This improvement can be justified by the increase in PbF2 reducing the multiphoton decay toward the 4F9/2 level and favoring thermal coupling. Finally, in a comparative analysis between a Ce3+/Nd3+- codoped aluminosilicate glass-ceramic and glass, we verified that the LIR between the 4F7/24I9/2 and 4F5/24I9/2 transitions have generated SR=1331/T2 in the glass sample. Furthermore, when an-alyzing the emissions of the Nd3+ between 850 nm- 1500 nm as a function of temperature, we have verified an enhancement in the emission at 1200 nm (4F5/2  4I13/2), probably as a conse-quence of thermal coupling between the 4F5/2 and 4F3/2 levels. Using the LIR between 4F5/2  4I13/2 and 4F3/2  4I11/2, we reached SA=3,110-4 K-1 at 450.15 K and SR = 1496.3/T2 in alumi-nosilicate glass-ceramic sample. Therefore, the three glass classes are promising candidates for developing the thermal sensors with their respective changes in chemical composition and heat treatment.