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Micro and submicrometric particles of luminescent alumina doped with chromium ions: synthesis by spray pyrolysis, structural and spectroscopic study for photonic applications

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Author(s):
Euzane Gomes da Rocha
Total Authors: 1
Document type: Master's Dissertation
Press: Ribeirão Preto.
Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC)
Defense date:
Examining board members:
José Maurício Almeida Caiut; Paula Sílvia Haddad Ferreira; Shirley Nakagaki
Advisor: José Maurício Almeida Caiut
Abstract

The development of Photonics, an area of science dedicated to studying optical phenomena, such as generation, manipulation, transport, and detection of light, and which has the photon as its basic unit, depends on the preparation of new materials and the understanding of the light-matter interaction. The initial milestone was given by the construction of the first ruby laser in 1969 by Theodore Maiman and from then on, the rapid development allowed the production of displays, scanners, data processors, medical therapies, among many other devices; however, there is still a lot to go forward. This work has its objectives directly inserted in the field of Photonics and aims at the synthesis, morphological, structural, and spectroscopic characterization of spherical ruby particles from aerosol pyrolysis, an easily scalable methodology from laboratory to industry; in addition to the production of composite films from particles and silk fibroin. Different characterization techniques were used and confirmed the formation of spherical particles of polycrystalline alumina doped with Cr3+ ions, either in the γ or α-Al2O3 phases. The spectroscopic characterization evidenced the influence of the crystalline field on the chromium ion, confirming changes in the ion coordination environment from the distinct colors for the different phases of the alumina. At the α-Al2O3, the intense red emission resulting from the 2El → 4A2 transition in the region of 693 nm, with the splitting referring to the R-lines of ruby, was characterized, and this emission was the focus of study for the development of photonic materials. The theoretical study of laser emission in a random environment determined the laser threshold energy at 5.9 J/cm2. Spectroscopic studies of photoluminescence as a function of temperature confirmed that despite the small energy difference of ~30 cm-1 between sublevels, ruby particles have a relative thermal sensitivity comparable to other materials described in the literature, enabling them to be used as luminescent thermometers at cryogenic temperature, or even close to room temperature. (AU)

FAPESP's process: 19/07175-7 - Micro and sub-micrometric particles of luminescent alumina: synthesis, structural and spectroscopic studies for photonic applications
Grantee:Euzane Gomes da Rocha
Support type: Scholarships in Brazil - Master