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DANIEL PRADO DA FONSECA
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Influence of synthesis conditions on the structural and luminescent properties of Ca2SiO4 obtained by sol-gel combustion.
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Advisor : HEVESON LUIS LIMA DE MATOS
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COMMITTEE MEMBERS :
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HEVESON LUIS LIMA DE MATOS
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JORGE LUIS OLIVEIRA SANTOS
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OSCAR MANOEL LOUREIRO MALTA
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ROMUALDO SANTOS SILVA JUNIOR
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Data: Sep 25, 2026
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Show Abstract
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Luminescent materials have attracted increasing scientific and technological interest due to their applications in optoelectronic devices, sensors, and energy conversion systems. Among host matrices, calcium silicates stand out for their high thermal and chemical stability, with beta-Ca2SiO4 being a promising candidate for rare-earth ion incorporation. In this work, the synthesis and structural and optical characterization of Eu3+-doped beta-Ca2SiO4 were investigated using a hybrid sol-gel combustion method. Samples with different dopant concentrations (0–1.0%) were prepared and subjected to thermal treatment in order to evaluate the influence of synthesis conditions on morphology, crystallinity, and luminescent performance. X-ray diffraction confirmed the predominant formation of the beta phase, while FTIR analyses evidenced the consolidation of the silicate network and the removal of residual nitrate species after thermal treatment. Emission spectra exhibited the characteristic Eu3+ transitions, with prominent red emission associated with the 5D0->7F2 transition, indicating effective dopant incorporation into the host lattice. The results demonstrate a strong correlation between synthesis method, structural organization, and luminescent efficiency, contributing to the development of silicate-based phosphors with potential technological applications.
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2
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ALINNE MELISSA RODRIGUES DE OLIVEIRA
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Quantum Caloric Effects of Power-Law Potentials: A Thermodynamic Characterization
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Advisor : CLEBSON DOS SANTOS CRUZ
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COMMITTEE MEMBERS :
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CLEBSON DOS SANTOS CRUZ
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ELIAS BRITO ALVES JUNIOR
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MARON FREITAS ANKA
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Data: Sep 30, 2026
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Show Abstract
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The recent Quantum Caloric Effect (QCE) bridges the gap between classical and quantum thermodynamics, providing novel insights into heat-exchange processes at the quantum level. In this work, we introduce the application of the QCE to quantum systems characterized by generalized power-law potentials, which include the infinite square well and the quantum harmonic oscillator as limiting cases. By examining these paradigmatic models, we elucidate how discrete energy spectra critically influence caloric responses, revealing fundamental distinctions compared to their classical counterparts. In particular, we derive analytical expressions for the isothermal entropy change ($\Delta S_{iso}$) and the adiabatic temperature variation ($\Delta T_{ad}$) for the Quantum Harmonic Oscillator and the Infinite Square Well. We extend this analysis to the generalized power-law potential, incorporating the semiclassical approximation of canonical entropy. Finally, we outline perspectives for applying this framework to multi-spin systems, such as dimers and trimers, aiming to characterize the intrinsic caloric potential of quantum materials and their implications for quantum thermal machines.
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