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- Structural and Optical Characterization of Mechanochemically Synthesized CuSbS2† [Abstract]Publication . Esperto, Luís; Figueira, Isabel; Mascarenhas, João; Silva, Teresa; Correia, J.B.; Neves, FilipeABSTRACT: The present work describes experimental studies related to the characterization of CuSbS2 directly synthesized after 2 h of mechanochemical synthesis (MCS) at 340 rpm, starting from mixtures of elemental powders. X-ray diffraction (XRD) and UV-VIS-NIR spectroscopy were carried out to analyze the crystal structure, degree of crystallinity, crystallite size and optical properties of the mechanochemically synthesized CuSbS2 powders. Rietveld refinement was carried out using Diffrac. TOPAS (Bruker AXS). Thermal stability of the synthesized materials was evaluated by the vacuum thermal heat treatment of the mechanochemically synthesized CuSbS2 powders at 350 °C for 24 h. Furthermore, the CuSbS2 powders were also analyzed by field-emission scanning electron microscopy (FE-SEM), laser diffraction, and differential thermal analysis.
- Processamento de materiais termoelétricos baseados na tetraedrite usando minério de tetraedrite-tenantitePublication . Esperto, Luís; Figueira, Isabel; Mascarenhas, João; Salgueiro, Rute; Silva, Teresa; Lopes, E.B.; Gonçalves, António Pereira; Correia, J.B.; de Oliveira, Daniel Pipa Soares; Almeida, P.; Neves, FilipeRESUMO: O desenvolvimento e implementação de tecnologias com baixo potencial de aquecimento global e energeticamente eficientes requer uma contínua inovação na área dos materiais para a energia. Nesta estratégia insere-se a pesquisa sobre o processamento de materiais termoelétricos baseados na tetraedrite. No presente trabalho procede-se à avaliação da viabilidade da incorporação direta, sem qualquer pré-tratamento, de minério da série tetraedrite-tenantite no processamento de materiais à base de tetraedrite por síntese mecanoquímica. Para tal prepararam-se misturas de pós contendo diferentes rácios de amostras de tetraedrite sintética, também obtida por síntese mecanoquímica, e de amostras de minério, recolhidas na mina de Neves-Corvo e na escombreira da mina do Barrigão. A caraterização estrutural e microestrutural dos materiais processados após 1 h e 2 h de síntese mecanoquímica permitiu verificar a formação de um composto constituído por tetraedrite-tenantite-(Fe) como fase principal, independentemente do minério de origem. Estes resultados são uma indicação do sucesso da abordagem seguida.
- Structural and optical characterization of mechanochemically synthesized CuSbS2 compoundsPublication . Esperto, Luís; Figueira, Isabel; Mascarenhas, João; Silva, Teresa; Correia, J.B.; Neves, FilipeABSTRACT: One of the areas of research on materials for thin-film solar cells focuses on replacing In and Ga with more earth-abundant elements. In that respect, chalcostibite (CuSbS2) is being considered as a promising environmentally friendly and cost-effective photovoltaic absorber material. In the present work, single CuSbS2 phase was synthesized directly by a short-duration (2 h) mechanochemical-synthesis step starting from mixtures of elemental powders. X-ray diffraction analysis of the synthesized CuSbS2 powders revealed a good agreement with the orthorhombic chalcostibite phase, space group Pnma, and a crystallite size of 26 nm. Particle-size characterization revealed a multimodal distribution with a median diameter ranging from of 2.93 mu m to 3.10 mu m. The thermal stability of the synthesized CuSbS2 powders was evaluated by thermogravimetry and differential thermal analysis. No phase change was observed by heat-treating the mechanochemically synthesized powders at 350 degrees C for 24 h. By UV-VIS-NIR spectroscopy the optical band gap was determined to be 1.41 eV, suggesting that the mechanochemically synthesized CuSbS2 can be considered suitable to be used as absorber materials. Overall, the results show that the mechanochemical process is a viable route for the synthesis of materials for photovoltaic applications.
- Characterization of Cu2ZnSn(SSe)4 monograin powders by FE-SEMPublication . Neves, Filipe; Livramento, Vanessa; Martins, Isabel M.; Esperto, Luís; Santos, Mário J. G.; Correia, J.B.; Muska, K.; Holopainen, T.The design and synthesis of high-efficiency materials to convert solar to electrical energy is an increasingly important research field. Within the photovoltaic technologies, crystalline Si have an 80% share while the remaining 20% are mostly thin film solar cells based on Cu(In,Ga)(S,Se)2 (CIGSSe) and CdTe [1,2].
- Recovery of mining waste as source of raw material for the synthesis of tetrahedrite-tennantite materials [Resumo]Publication . Neves, Filipe; Esperto, Luís; Figueira, Isabel; Mascarenhas, João; Salgueiro, Rute; Silva, Teresa; Correia, J.B.; Carvalho, Patricia Almeida; De Oliveira, Daniel Pipa Soares
- Characterization of Cu2ZnSn(SSe)4 monograin powders by FE-SEMPublication . Neves, Filipe; Livramento, Vanessa; Martins, Isabel M.; Esperto, Luís; Santos, Mário J. G.; Correia, J.B.; Muska, K.; Holopainen, T.The design and synthesis of high-efficiency materials to convert solar to electrical energy is an increasingly important research field. Within the photovoltaic technologies, crystalline Si have an 80% share while the remaining 20% are mostly thin film solar cells based on Cu(In,Ga)(S,Se)2 (CIGSSe) and CdTe [1,2]. However,the cost, the abundance and the environmental impact of the elemental components cannot be neglected. For these reasons, Cu2ZnSnS4 (CZTS), Cu2ZnSnSe4 (CZTSe)and their solid solutions CZTSSe has attracted much attention recently since they can provide the development of cost competitive solar cells. The CZTS-based solar cells consist of earth abundant and relatively inexpensive elements and represent an environmentally friendly alternative compared to the above mentioned systems [3]. The energy conversion efficiency of the CZTS-based solar cells has increased from 0.66% in 1996 to 11.1% recently [4].
- Mechanochemical synthesis of tetrahedrite materials using mixtures of synthetic and ore samples collected in the Portuguese zone of the Iberian Pyrite BeltPublication . Neves, Filipe; Esperto, Luís; Figueira, Isabel; Mascarenhas, João; Salgueiro, Rute; Silva, Teresa; Correia, J.B.; Carvalho, Patricia Almeida; de Oliveira, Daniel Pipa SoaresABSTRACT: Considering that the synthesis of tetrahedrite-based materials usually uses high purity elements, the evaluation of the direct application of ore samples as raw materials for their synthesis is a pertinent issue. In the present study, multiphase synthetic tetrahedrite samples were mixed with tetrahedrite-tennantite ore samples (in weight ratios of 0.8/0.2, 0.5/0.5 and 0.2/0.8) to produce tetrahedrite-based materials by solid-state mechanochemical syn-thesis. The ore samples were obtained from the abandoned Barrig ̃ao mine dumps and from the Neves Corvo mine, both located in the Portuguese zone of the Iberian Pyrite Belt, whose main constituents were found to be As-rich tetrahedrite and tennantite-(Fe), respectively. Depending on the ore sample and on the mixture ratios, the displacement reactions occurring during the synthesis process gave rise to different phase transformation paths. For the ratios of 0.5/0.5 and 0.2/0.8, the mixtures with the Barrig ̃ao ore were found to consist of a single sulfide phase, tetrahedrite-tennantite-(Fe), plus quartz, while famatinite was also observed in the 0.8/0.2 mixture. Tetrahedrite-tennantite-(Fe) phase was the main constituent of all mixtures with the Neves Corvo ore, but in all of them other sulfide phases, famatinite-luzonite and pyrite, were also present in addition to quartz. Despite being dissimilar, these results are very promising and encouraging, by confirming the possible direct usage of ore samples and of dump material for the synthesis of tetrahedrite-based materials with all the potential environmental-economic gains that can be obtained.
- Recursos locais para aplicações multifuncionais de captação de energia com base em tetraedritePublication . Neves, Filipe; Esperto, Luís; Figueira, Isabel; Mascarenhas, João; Correia, J.B.; Joyce, A; Guimarães, Fernanda; Salgueiro, Rute; Silva, Teresa; de Oliveira, Daniel Pipa Soares; Lopes, E.B.; Gonçalves, António Pereira; Centeno, Pedro; Mendes, M.J.; Águas, H.; Martins, Rodrigo; Gil, Luís; Almeida, PatríciaRESUMO: Este trabalho descreve as principais linhas de investigação que estão em curso no âmbito do projeto LocalEnergy (http://localenergy.lneg.pt). LocalEnergy é um projeto multidisciplinar de Investigação, Desenvolvimento e Inovação (I&D&I), envolvendo atividades no domínio da ciência dos materiais, da geologia e das energias renováveis. Essas atividades estão orientadas para a indústria e assentam numa abordagem disruptiva visando o desenvolvimento de materiais termoelétricos, através da utilização de materiais à base de tetraedrites naturais e sintéticas, e o desenvolvimento de novos absorsores para células solares de filmes finos, usando materiais à base de tetraedrites sintéticas. Considerando que Portugal é um dos países europeus com maior nível de irradiação de energia solar e que a tetraedrite é um recurso mineral local, presente na Zona Sul Portuguesa da Faixa Piritosa Ibérica, o projeto LocalEnergy representa uma oportunidade para o desenvolvimento de sistemas energéticos sustentáveis baseados na maximização e exploração de dois importantes recursos endógenos (energia solar e recursos minerais).
- LocalEnergy: Local Resources for Multifunctional Tetrahedrite-based Energy: Harvesting ApplicationsPublication . Neves, Filipe; Correia, J.B.; Esperto, Luís; Mascarenhas, João; Figueira, Isabel; de Oliveira, Daniel Pipa Soares; Salgueiro, Rute; Silva, Teresa; Santos, Beatriz; Lopes, E.B.; Gonçalves, António Pereira; Centeno, Pedro; Fortunato, Elvira; Martins, Rodrigo; Águas, Hugo; Mendes, Manuel Joao
- Powder sintering of single-phase tetrahedrite materials [Resumo]Publication . Neves, Filipe; Esperto, Luís; Figueira, Isabel; Mascarenhas, João; Correia, J.B.; Ferreira, H.; Lopes, E.B.; Gonçalves, António PereiraABSTRACT: There is a worldwide consensus for the development and implementation of zero global-warming-potential and energy efficient technologies. This energy transition requires more progress in all aspects related with renewable technologies, including the research and innovation on new and improved materials, e.g., materials for converting thermal wasted energy into electricity.