DSpace Coleção:http://repositorio.ufc.br/handle/riufc/3012026-04-10T19:55:27Z2026-04-10T19:55:27ZSynthesis and characterization of a hybrid perovskite with an imidazole spacer for optoelectronic applicationsBraga, Ednara Joicehttp://repositorio.ufc.br/handle/riufc/853012026-03-11T13:38:05Z2025-01-01T00:00:00ZTítulo: Synthesis and characterization of a hybrid perovskite with an imidazole spacer for optoelectronic applications
Autor(es): Braga, Ednara Joice
Abstract: Perovskites are an emerging class of materials that have attracted significant attention from the scientific community due to their semiconductor properties. Three-dimensional hybrid
perovskites demonstrate good performance in optoelectronic devices, such as solar cells and light-emitting diodes (LEDs). The predominant use of lead ions (Pb²⁺) in the composition of perovskites, although effective in terms of efficiency, raises concerns related to toxicity and limited stability under ambient conditions. In this context, tin (Sn) has emerged as a promising substitute for lead, reducing toxicity without compromising performance. In addition to replacing Pb with Sn, the incorporation of novel organic cations into the structure of hybrid perovskites has been considered a promising strategy to improve their chemical and environmental stability. This modification leads to the formation of hybrid organic-inorganic metal halides, which enhance the structural integrity and influence the electronic and optical properties of the material. In this work, the hybrid perovskite (C₁₁H₁₁N₂O)₂SnBr₆ was synthesized using a slow evaporation method in an acidic medium. The structure incorporates the organic cation 2-(1H-imidazol-1-yl)-1-phenylethanone, while Sn⁴⁺ coordinates six bromide atoms, forming the [SnBr₆]²⁻ octahedron. The resulting crystalline organization is classified as a zero-dimensional (0D) perovskite, composed of isolated octahedral units. The compound exhibits broad-band emission across a large portion of the visible spectrum. This feature is associated with the radiative recombination of self-trapped excitons (STEs), a phenomenon commonly observed in hybrid halide perovskites. In addition to its structural stability, a key factor for practical applications, the perovskite displays a direct optical bandgap of 2.99 eV, making it a potential candidate for optoelectronic devices. Thus, this research contributes to the development of alternative materials that not only offer competitive performance compared to conventional lead-based perovskites but also address challenges related to sustainability and toxicity, broadening the scope for safe and efficient technological applications.
Tipo: Dissertação2025-01-01T00:00:00ZGoma do Anacardium occidentale L. : isolamento, caracterização e estudo reológicoPaula, Regina Célia Monteiro dehttp://repositorio.ufc.br/handle/riufc/848592026-02-20T14:15:30Z1990-01-01T00:00:00ZTítulo: Goma do Anacardium occidentale L. : isolamento, caracterização e estudo reológico
Autor(es): Paula, Regina Célia Monteiro de
Abstract: The objeclive of this work was to make a study of the Pnacardium occidentate qum from Northeast of Brasil. [...]
Tipo: Dissertação1990-01-01T00:00:00ZContribuição ao estudo químico de plantas do Nordeste: Thiloa Glaucocarpa e Combretum Sp.Militão, Júlio Sancho Linhares Teixeirahttp://repositorio.ufc.br/handle/riufc/844492026-01-24T00:36:05Z1990-01-01T00:00:00ZTítulo: Contribuição ao estudo químico de plantas do Nordeste: Thiloa Glaucocarpa e Combretum Sp.
Autor(es): Militão, Júlio Sancho Linhares Teixeira
Tipo: Dissertação1990-01-01T00:00:00ZPropriedades dielétricas do compósito (La2Zr2O7) x:(La2Ti2O7)1-x em rf e micro-ondasNogueira, Emanoel Lindimar Macielhttp://repositorio.ufc.br/handle/riufc/843512026-01-19T20:30:59Z2025-01-01T00:00:00ZTítulo: Propriedades dielétricas do compósito (La2Zr2O7) x:(La2Ti2O7)1-x em rf e micro-ondas
Autor(es): Nogueira, Emanoel Lindimar Maciel
Abstract: Composites, materials formed by combining two or more distinct constituents, can be employed in the design of novel dielectric resonators with applicability in dielectric resonator antennas (DRAs). With the rapid development of telecommunication technologies, particularly 5G, satellites, wireless communication devices, and GPS (Global Positioning System), there is a growing demand for the improvement and development of electronic devices based on electroceramics for microwave (MW) and radiofrequency (RF) emission and reception systems. This work investigates the use of La2Zr2O7 (LZO), La2Ti2O7 (LTO), and their composites, ((La2Zr2O7) x: (La2Ti2O7)1-x where x = 0.25, 0.50, 0.75) as dielectric resonator antennas (DRAs) operating in the MW and RF ranges. The materials were synthesized by the solid-state reaction method and characterized using X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). Subsequently, their dielectric properties were studied in the RF range under varying temperatures by impedance spectroscopy (IS), as well as in the MW range. The composites exhibited dielectric constant (εr) values between 22 and 43. Regarding the temperature coefficient of resonant frequency (τf), values ranged from −14 to 33 ppm·°C⁻¹. The addition of LZO into the LTO matrix induced significant changes in the electrical and dielectric properties. Both pure phases and composite samples exhibited thermally activated dielectric relaxation processes at high frequencies and temperatures, with activation energies depending on the LZO content.
Tipo: Dissertação2025-01-01T00:00:00Z