Estudo da cinética de cristalização e dos parâmetros térmicos de vidros fosfato dopados com terra-rara

Abstract

In the present work the kinetics of crystallization and the thermal parameters of glass phosphates with the system 𝑃2𝑂5 − 𝑆𝑖𝑂2 − 𝑁𝑎2𝑂 − 𝑍𝑛𝑂 − 𝐶𝑎𝑂 − 𝑀𝑔𝑂 − 𝐴𝑙2𝑂3 doped with different concentrations of 𝑁𝑑2𝑂3 (0.1 , 0.2 , 1.0 e 2.0 in mol%) were studied . The system was developed for application in areas such as photonics and vitro-ceramics, both on the scientific and industrial scale. Such a system is unprecedented and relatively cheaper compared to others, such as, for example, Silicon and Tellurium based glass. In view of the general objective, the research was developed in stages, being: first the choice of components (reagents) of the system; the second to sample syntheses varying the dopant concentration; and the third the characterization using the techniques of Differential Thermal Analysis (DTA), Thermogravimetry (TGA) and X-ray Diffraction (XRD) using a Jupiter® STA 449 F3 Simultaneous Thermal Analyzer located at the Centro de Pesquisa em Materiais (CPEM) and a D8 Advance DaVinci Diffractometer located in the Núcleo de Espectroscopia e Estrutura Molecular (NEEM), both laboratories of the UFJF. In order to verify the crystallization of the system, samples of base glass (matrix) and doped with 1.0mol% Nd were conditioned to an isothermal treatment, at 450ºC and 500°C the base glass, and 450ºC, 500ºC and 600°C glass 1.0mol% Nd for one hour and thirty minutes. The parameters of glassy stability (GS parameters) were calculated using the results obtained from Differential Thermal Analysis, these results were also used for calculations of crystallization and nucleation kinetics. Nucleation and crystal growth were studied under non-isothermal conditions by the Kissinger-Ligero method, determining the values of the Activation Energy for Crystallization and the Avrami parameter for the system