Orientador: Elson Longo da Silva / Banca: Paulo Lisboa Noronha Filho / Banca: Máximo Siu Li / Banca: Paulo Sérgio Pizani / Banca: Luis Presley Serejo dos Santos / Resumo: Cristais de PbMoO4 foram obtidos por intermédio do método coprecipitação (CP) a temperatura ambiente e processadas em diferentes temperaturas (60oC-120oC) por 10 minutos utilizando o método processamento hidrotérmico (PH). Os micros octaedros foram caracterizados estruturalmente por intermédio de técnica de difração de raios X (DRX), refinamento estrutural de Rietveld, espectroscopia de micro-Raman (MR) e de absorção no infravermelho (IVTF). Suas propriedades ópticas foram investigadas por intermédio das técnicas de espectroscopia de ultravioleta visível (UV-Vís) e de fotoluminescência (FL). Os padrões de difração de raios X e os espectros de micro-Raman indicaram que estes cristais possuem uma estrutura tipo scheelita com estrutura cristalina tetragonal sem a presença de fases secundárias. Os dados de refinamentos Rietveld foram empregados a fim de monitorar as diferenças estruturais nos pós de PbMoO4 preparados pelos dois métodos. Os espectros de MR mostraram um modo de vibração ν1 (Ag), situado na em torno de 876 cm-1, o qual está relacionado com as vibrações simétricas de alongamento da ligação Mo-O nos clusters [MoO4]. Espectros de IVTF apresentaram uma banda larga de absorção com dois modos ν3 (Eu e Au), localizada cerca de 749 e 756 cm-1, para PbMoO4 obtido pelo método de CP e 864 e 851 cm-1 para PbMoO4 obtidos pelo método de PH em diferentes temperaturas. Esses modos vibracionais estão associados ao alongamento antisimétrico O-Mo-O nos clusters [MoO4]. As imagens de microscopia eletrônica de varredura de campo induzido (MEV-FEG) foram empregadas para observar as morfologias dos materiais e acompanhar a evolução do crescimento e transformação desses cristais. Medidas de UV-Vís evidenciaram um aumento nos valores de band gap (3,14 eV a 3,19 eV) com o aumento da temperatura de processamento hidrotérmico. As propriedades PL foram explicadas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: PbMoO4 crystals have been obtained by means of coprecipitation (CP) method at room temperature and processed at different temperatures (60oC -120oC) for 10 minutes by using conventional hydrothermal method (CH). These micro-octahedrons were structurally characterized by means of X-ray diffraction (XRD), Rietveld refinements, micro-Raman (MR) and Fourier transformed infrared (FTIR) spectroscopies. Their optical properties were investigated by ultraviolet visible (UV-vis) absorption and photoluminescence (PL) measurements. XRD patterns and micro-Raman spectra indicated that these crystals have a scheelite-type tetragonal structure without the presence of deleterious phases. Rietveld refinements data were employed in order to monitor the structural differences into PbMoO4 lattice of the crystals prepared by two methods. MR spectra showed a high mode ν1 (Ag) situated at around 876 cm-1, which is related to the Mo-O symmetric stretching vibrations into the [MoO4] clusters. FTIR spectra exhibited a large absorption band with two modes ν3 (Eu and Au) located at around 749 and 756 cm-1, for PbMoO4 obtained by CP method and 864 and 851cm-1 for PbMoO4 obtained by PH at different temperatures, which are associated to the O-Mo-O antisymmetric stretching vibrations into the [MoO4] clusters. Field emission gun scanning electron microscopy (FEG-SEM) micrographs were employed to observe the shape and monitor the evolution of growth and processing of these crystals. UV-vis absorption measurements evidenced a reduction in optical band gap values (from 3,14 eV to 3,19 eV) with the increase of CH processing temperature. PL properties of were explained through a model based in distortions on the tetrahedral [MoO4] clusters due to intrinsic defects at medium range and presence of intermediary energy levels (deep and shallow holes) within the band gap. Finally, the growth mechanisms were proposed for... (Complete abstract click electronic access below) / Doutor

Doctor of Philosophy / Department of Chemistry / Emily McLaurin / Semiconductors are materials whose conductivity is between metals and insulators. Semiconductor nanocrystals (NCs) have sizes in the range 2 to 10 nm. Because of their unique optical properties like tunable emission wavelength, narrow emission peak, and stability over dyes, they have potential applications in displays. Indium phosphide (InP) is considered a less toxic alternative to commercially used cadmium-based semiconductor NCs. Microwave-assisted (MA) methods using ionic liquids (ILs) afford fast reaction heating rates because of the good MW absorbing capacity of ILs. For tuning size and surface, which are some of the important problems associated with the InP NCs, new synthetic methods are reported herein. In MAIL etching HF generated in the microwave reaction etches the InP NCs surface. Pyridinium and imidazolium based ILs containing tetrafluoroborate (BF₄⁻) and hexafluorophosphate (PF₆⁻) ions yield luminescent NCs. In a silicon carbide (SiC) reaction vessel, which blocks most of the microwaves penetrating into the reaction, bigger NCs form than those from a Pyrex reaction vessel because of the higher reaction temperatures in the SiC vessel. By changing microwave set-power (SP), different reaction times can be achieved. Though a small degree of change in average NC diameter of the NCs is observed at different SPs and reaction temperatures, addition of dodecylamine (DDA) yields NCs with average sizes between 3.2 to 4.2 nm with a broad size distribution. At lower SPs smaller NCs form and at higher SPs bigger NCs form. NC luminescence can be tuned from green (545 nm) to red (630 nm) in the visible region with quantum yields as high as 30%. Rapid heating and InP precursor activation might be responsible for the larger change in NC size. The effect of DDA on NC size is also verified by microwave reactions in SiC vessels. ILs containing PF₆⁻ ions at 280 °C will modify the surface of the NCs so the NC dispersibility changes from non-polar (toluene) to polar (DMSO) as the amount of IL increases. This is due to ligand stripping, which is the removal of large palmitic ligands from the NC surface. These NCs have broad absorption features and emission peaks with QYs of up to 30%. Fourier transform infrared spectroscopy indicates the absence of palmitic acid ligands on the NC surface and zeta potential measurements indicate the presence of anions on the NC surface. From X-ray photoelectron spectroscopy and nuclear magnetic resonance spectroscopy, the inorganic ion PO₂F₂⁻ is identified on the NCs surface.

Title: Photoluminescence of CdTe crystals Author: Jan Procházka Department: Institute of Physics of Charles University in Prague Supervisor: Doc. RNDr. Pavel Hlídek, CSc. Abstract: Energy levels connected with defects in nominally undoped crystals CdTe, indium- doped crystals and chlorine-doped crystals were studied using low-temperature photoluminescence. The crystals are intended for X- and gamma- ray detectors operated at room temperature. An effect of annealing in cadmium or tellurium vapor on luminescence spectra was investigated. Some changes were interpreted by filling of vacancies not only by atoms coming from gaseous phase but also by impurities from defects like interstitials, precipitates, inclusions, grain boundaries etc. The luminescence bands assigned to defects important for compensation mechanism were examined, namely A-centers (complexes of vacancy in cadmium sublattice and impurity shallow donor) and complexes of two donors bound to a vacancy. It was shown, that temperature dependence of the luminescence bands results from more complicated processes than a simple thermal escape of bound excitons or thermal excitation of electrons (holes) from defects to bands. We observed expressive "selective pair luminescence" bands (SPL) on partially compensated In-doped samples during sub-gap...

>Magister Scientiae - MSc / The efficiency of organic photovoltaics is influenced by the structure of the polymer, the morphology of the film, the interfaces between the layers, the choice of electron acceptor material and the ratio between the electron acceptor material and the polymer. In this project, we have used regioregular poly (3-hexylthiophene) (rr-P3HT) as the electron donor material and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), a derivative of the C60 fullerene, as the acceptor material. Different weight-ratios of rr-P3HT to PCBM were prepared by stirring for several hours in a chloroform solution and subsequently spin coated onto crystalline silicon and transparent conductive oxide/glass substrates. The effect of the PCBM concentration on the photo-induced optical emission and absorption properties of rr-P3HT was investigated by photoluminescence and ultraviolet-visible spectroscopy, respectively. Changes in the structural properties, as a function of the weight-ratio, were probed by high-resolution transmission electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy. Results show that the structural integrity and crystallinity of rr-P3HT is compromised with the addition of excessive amounts of PCBM, which has a negative impact on the optical absorption of rr-P3HT and the photo-induced charge transfer mechanism between the rr-P3HT and PCBM. This work illustrates that blending rr-P3HT with an equal weight of PCBM results in an optimum configuration for improved performance in organic photovoltaic devices.

Nanofios semicondutores de óxido metálico apresentam enorme potencial em aplicações de nano-sensoriamento de diferentes gases e substâncias químicas e biológicas, bem como na aplicação a detectores UV-visível. Neste trabalho, desenvolvemos e aperfeiçoamos a síntese de nanofios de ZnO em substratos de safira (001), silício (111) e silício (100) sob diferentes concentrações de oxigênio usando o processo de transporte de vapor-liquido-sólido (VLS). No presente trabalho, investigamos a influência da concentração de oxigênio no crescimento de nanofios de ZnO por Espectroscopia de Fotoluminescência a temperatura variável com a finalidade de estudo da mudança na concentração de defeitos. Apresentamos, ainda, caracterizações elétricas (IxV e Ixt) de nanoestruturas de ZnO sob diferentes pressões com o objetivo de estudar os defeitos envolvidos nos processos de transportes eletrônicos. Por último, propomos o desenvolvimento de micro-contatos através da técnica de microfeixe iônico e através de nanolitografia por feixe de elétrons com a finalidade de aplicações a sensores químicos, gasosos e fotodetectores. / Metal oxide nanowires semiconductors have enormous potential in high-sensitive, fast and selective sensing applications. It may be used to selectively detect different gases, chemical and biological substances and also in UV-visible photodetectors. The described processes involve the synthesis as well as the characterization of ZnO nanowires grown on sapphire (001), silicon (100) e silicon (111) substrates by the Vapor-liquid-solid transport method. In the present work, we describe the influence of oxygen concentration introduced in the growth step measured by photoluminescence at variable temperature to demonstrate the change in defect levels emission (DLE). Furthermore, we have shown electrical characterization (IxV and Ixt) in order to study the ambient effect for transport mechanisms in ZnO nanowires. We also report the development of crucial steps in the fabrication for an upcoming ZnO nanowire sensor device (gas, chemical and photodetector) using lithography techniques such as ion micro-beam and electron beam with the purpose of fabricating metallic micro-pads.

Neste trabalho se realiza a síntese e caracterização de nanofios de óxido de zinco. Adicionalmente se apresenta o processo de montagem de um dispositivo para medidas elétricas deste material. Estuda-se complementarmente o efeito do tratamento de plasma sobre as propriedades de fotoluminescência do material. Nanofios foram sintetizados pelo mecanismo vapor-líquido-sólido (VLS), utilizando ouro como catalizador e safira c-plane como substrato. As amostras foram caracterizadas utilizando microscopia eletrônica de varredura, fotoluminescência a temperatura ambiente, difração de raios X, e microscopia eletrônica de transmissão. Os nanofios obtidos têm seção transversal com formato quase hexagonal, e larguras de aproximadamente 46 nm. O comprimento deles varia de 3 a 10 μm. Os resultados de difração de raios x e microscopia eletrônica de transmissão mostram que eles são monocristalinos com rede cristalina tipo wurtzita, e com direção de crescimento no eixo c. Foram estudados os efeitos da potência de plasma de oxigênio (O2) na fotoluminescência dos nanofios a temperatura ambiente. A diferença na fotoluminescência após diferentes tratamentos de plasma de O2 mostra que a razão entre a emissão da região do band gap e da banda do visível pode ser modificada pelo tratamento. Este efeito corrobora com a hipótese de que a banda verde de luminescência está relacionada às vacâncias de zinco. A variação percentual da razão entre as duas regiões apresenta uma dependência linear com a potência do plasma. / In this work, we performed the synthesis and characterization of zinc oxide nanowires. We also report an assembly process to measure the electrical properties of this material. We study the plasma treatment effect on the photoluminescence spectra of the nanowires. Nanowires were synthesized via vapor-liquid-solid mechanism, using gold as catalyst and c-plane sapphire as substrate. The samples were characterized using scanning electron microscopy, room temperature photoluminescence, x-rays diffraction and transmission electron microscopy. Our nanowires show a quasi-hexagonal cross section, with diameters of approximately 46 nm. Their lengths ranged from 3 to 10 μm. Our results show monocrystalline wurtzite crystal nanowires with c growth direction. We also study the plasma power effect of oxygen (O2) plasma treatment on the room temperature photoluminescence spectra of the nanowires. Our results show that the deep level emission to near band emission ratio decreases with the plasma treatment. This effect supports the hypothesis that claims the green band luminescence is related to the oxygen vacancies. Furthermore, the relative ratio change depends linearly on the plasma power.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / O objetivo deste trabalho foi a produção e a investigação de amostras cerâmicas dopadas com Fe3+. Os métodos experimentais usados foram a difração de raios X, e as espectroscopias de fotoluminescência e fotoacústica. As fases formadas foram identificadas a partir dos resultados da difração de raios X. Utilizando os dados ópticos, os níveis de energia excitados e o fundamental, os parâmetros de energia e de campo cristalino e de Racah, os tempos de vida radiativos e não-radiativos e a simetria do sítio do Fe3+ foram determinados. / The aim of this work was the production and investigation of a Fe3+- doped sample. The experimental methods were X-ray diffraction, photoluminescence and photoacoustic spectroscopies. From X-ray results, the formed phases in the sample were identified. By using optical data, the excited and fundamental energy levels, the energy crystal field and Racah parameters, the radiative and non-radiative lifetimes and the Fe3+ site symmetry were determinated.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Esta dissertação apresenta as espectroscopias de fotoluminescência e de excitação de amostras MgGa2O4 dopadas com 0,5% e 10,0% de Mn2+, obtidas com temperatura ambiente. As amostras policristalinas foram produzidas por reação de estado sólido sob alta temperatura no Laboratório de Preparação e Caracterização de Materiais do IFGW da UNICAMP e caracterizadas por Difração de Raios X no Laboratório de Cristalografia e Difração de Raios-X do Centro Brasileiro de Pesquisas Físicas (CBPF), e por Microscopia Eletrônica de Varredura (MEV) na PUC-RIO e no Instituto de Biologia Roberto Alcântara Gomes (IBRAG-UERJ). Os espectros de fotoluminescência mostraram emissões nas regiões espectrais do verde e do vermelho, para ambas as dopagens e foram analisados com base na teoria de Tanabe-Sugano. As emissões foram atribuídas à transição eletrônica proibida por spin 4T1(4G) → 6A1(6S) do íon impureza Mn2+ em sítios coordenados por oxigênios, com simetria tetraédrica (luminescência verde) e octaédrica (luminescência vermelha). A partir dos espectros de excitação, identificaram-se as transições de energia e com as matrizes de Tanabe-Sugano calcularam-se os parâmetros de campo cristalino e de Racah. / This work presents the room temperature photoluminescence and excitation spectroscopes data of MgGa2O4 samples doped with 0.5% and 10.0% Mn2+. The polycrystalline samples were produced by solid-state reaction at high temperature and characterized with X ray Diffraction and SEM. The photoluminescence spectra showed emission at green and red spectral regions, for both doping levels and were analyzed based on the Tanabe-Sugano Theory. The emissions were attributed to 4T1(4G) → 6A1(6S) spin-forbidden electronic transition of Mn2+ impurity ions in tetrahedral (green emission) and octahedral (red emission) oxygen coordinated sites. From excitation spectra, we identified the energy transitions and from Tanabe-Sugano matrices we calculated the crystal field and Racah parameters.

Made available in DSpace on 2014-06-11T19:32:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-17Bitstream added on 2014-06-13T19:42:33Z : No. of bitstreams: 1 delmonte_mrb_dr_araiq.pdf: 5366733 bytes, checksum: 51bba7b88f423a4eac52eb8d0154dc1f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Cristais de PbMoO4 foram obtidos por intermédio do método coprecipitação (CP) a temperatura ambiente e processadas em diferentes temperaturas (60oC-120oC) por 10 minutos utilizando o método processamento hidrotérmico (PH). Os micros octaedros foram caracterizados estruturalmente por intermédio de técnica de difração de raios X (DRX), refinamento estrutural de Rietveld, espectroscopia de micro-Raman (MR) e de absorção no infravermelho (IVTF). Suas propriedades ópticas foram investigadas por intermédio das técnicas de espectroscopia de ultravioleta visível (UV-Vís) e de fotoluminescência (FL). Os padrões de difração de raios X e os espectros de micro-Raman indicaram que estes cristais possuem uma estrutura tipo scheelita com estrutura cristalina tetragonal sem a presença de fases secundárias. Os dados de refinamentos Rietveld foram empregados a fim de monitorar as diferenças estruturais nos pós de PbMoO4 preparados pelos dois métodos. Os espectros de MR mostraram um modo de vibração ν1 (Ag), situado na em torno de 876 cm-1, o qual está relacionado com as vibrações simétricas de alongamento da ligação Mo-O nos clusters [MoO4]. Espectros de IVTF apresentaram uma banda larga de absorção com dois modos ν3 (Eu e Au), localizada cerca de 749 e 756 cm-1, para PbMoO4 obtido pelo método de CP e 864 e 851 cm-1 para PbMoO4 obtidos pelo método de PH em diferentes temperaturas. Esses modos vibracionais estão associados ao alongamento antisimétrico O-Mo-O nos clusters [MoO4]. As imagens de microscopia eletrônica de varredura de campo induzido (MEV-FEG) foram empregadas para observar as morfologias dos materiais e acompanhar a evolução do crescimento e transformação desses cristais. Medidas de UV-Vís evidenciaram um aumento nos valores de band gap (3,14 eV a 3,19 eV) com o aumento da temperatura de processamento hidrotérmico. As propriedades PL foram explicadas... / PbMoO4 crystals have been obtained by means of coprecipitation (CP) method at room temperature and processed at different temperatures (60oC -120oC) for 10 minutes by using conventional hydrothermal method (CH). These micro-octahedrons were structurally characterized by means of X-ray diffraction (XRD), Rietveld refinements, micro-Raman (MR) and Fourier transformed infrared (FTIR) spectroscopies. Their optical properties were investigated by ultraviolet visible (UV-vis) absorption and photoluminescence (PL) measurements. XRD patterns and micro-Raman spectra indicated that these crystals have a scheelite-type tetragonal structure without the presence of deleterious phases. Rietveld refinements data were employed in order to monitor the structural differences into PbMoO4 lattice of the crystals prepared by two methods. MR spectra showed a high mode ν1 (Ag) situated at around 876 cm-1, which is related to the Mo–O symmetric stretching vibrations into the [MoO4] clusters. FTIR spectra exhibited a large absorption band with two modes ν3 (Eu and Au) located at around 749 and 756 cm-1, for PbMoO4 obtained by CP method and 864 and 851cm-1 for PbMoO4 obtained by PH at different temperatures, which are associated to the O–Mo–O antisymmetric stretching vibrations into the [MoO4] clusters. Field emission gun scanning electron microscopy (FEG-SEM) micrographs were employed to observe the shape and monitor the evolution of growth and processing of these crystals. UV-vis absorption measurements evidenced a reduction in optical band gap values (from 3,14 eV to 3,19 eV) with the increase of CH processing temperature. PL properties of were explained through a model based in distortions on the tetrahedral [MoO4] clusters due to intrinsic defects at medium range and presence of intermediary energy levels (deep and shallow holes) within the band gap. Finally, the growth mechanisms were proposed for... (Complete abstract click electronic access below)

Made available in DSpace on 2016-06-02T20:36:56Z (GMT). No. of bitstreams: 1 6820.pdf: 31396624 bytes, checksum: baada275d7fcaaaca7447011730791b4 (MD5) Previous issue date: 2015-07-17 / Financiadora de Estudos e Projetos / The tungstates are important compounds and known for their optical properties. In this work, solid solutions with nickel silver tungstate, 𝐴𝑔2−2𝑥𝑁𝑖𝑥𝑊𝑂4, compositions (0, 01 ≤ 𝑥 ≤ 0, 08) were synthesized by the hydrothermal method of microwave to 140 ° C for 1 h, and to assess the influence of 𝑁𝑖2+ ions in the structural, morphological and photoluminescent of the silver tungstate (𝐴𝑔2𝑊𝑂4). Materials 𝐴𝑔2−2𝑥𝑁𝑖𝑥𝑊𝑂4 (0 ≤ 𝑥 ≤ 0.08) were characterized by X-ray diffraction (XRD), spectroscopy micro-Raman (MR) and absorption in the Infrared (IR) region. The scanning electron microscopy (SEM) was used for image recording surface of these ceramic oxides, while the energy dispersive X-ray technique (EDS) with mapping of chemical elements, was used to qualitatively determine the chemical composition of the samples. The optical properties were studied by electron spectroscopy in the region of ultraviolet-visible (UV-vis) in which the values of energy band gap (𝐸𝑔𝑎𝑝) were estimated, and by means of photoemission spectroscopy was studied effect of 𝑁𝑖2+ ions in photoluminescence (PL) of silver tungstate. The XRD patterns of the single-phase crystallization of all samples in the orthorhombic structure of the silver tungstate and they have indicated a long range structural order. Small changes in network parameters and atomic coordinates, indicate the existence of distortions on the cluster [𝐴𝑔𝑂𝑛] (𝑛 = 2, 4, 6 and 7) and [𝑊𝑂6] and inserting the 𝑁𝑖 atoms in the crystal lattice 𝛼-𝐴𝑔2𝑊𝑂4. Changes in MR spectra and peak detection regarding 𝑁𝑖 − 𝑂 bond in IR spectra of solid solutions suggest the introduction of 𝑁𝑖 atoms in the 𝐴𝑔2𝑊𝑂4 network.The SEM images showed that the ions 𝑁𝑖2+ were able to modify the morphology of silver tungstate microcrystals, in the studied conditions. The EDS spectra and map images indicated that all materials are composed of the elements 𝐴𝑔, 𝑊 and 𝑂, as expected. They also noted the presence of 𝑁𝑖 element in the composition of solid solutions. The values of 𝐸𝑔𝑎𝑝 estimated by means of UV-vis spectra suggest the existence of intermediate states in the forbidden area, from structural defects. The changes in spectra of PL samples indicated that the 𝑁𝑖 atoms alter the effect of the order-disorder, and the average distance favored over energy emissions associated with shallow defects. / Os tungstatos são compostos importantes e conhecidos por suas propriedades ópticas. Neste trabalho, soluções sólidas de tungstato de prata com níquel, 𝐴𝑔2−2𝑥𝑁𝑖𝑥𝑊𝑂4, nas composições de (0, 01 ≤ 𝑥 ≤ 0, 08) foram sintetizados pelo método hidrotérmico de microondas a 140 °C por 1h, visando investigar a influência dos íons 𝑁𝑖2+ nas propriedades estruturais, morfológicas e fotoluminescentes do tungstato de prata (𝐴𝑔2𝑊𝑂4). Os materiais (𝐴𝑔2−2𝑥𝑁𝑖𝑥𝑊𝑂4) (0 ≤ 𝑥 ≤ 0, 08) foram caracterizados estruturalmente por difração de raios X (DRX), espectroscopias micro-Raman (MR) e de absorção na região do Infravermelho (IV). A microscopia eletrônica de varredura (MEV) foi empregada para registro de imagens de superfície desses óxidos cerâmicos, enquanto que a técnica de energia dispersiva de raios X (EDX), juntamente com o mapeamento dos elementos químicos, foi utilizada para determinar qualitativamente da composição química das amostras. As propriedades ópticas foram estudadas pela espectroscopia eletrônica na região do ultravioleta-visível (UV-vis), no qual os valores das energias de band gap (𝐸𝑔𝑎𝑝) foram estimados, e por meio de espectroscopia de fotoemissão estudou-se efeito dos íons 𝑁𝑖2+ na fotoluminescência (FL) do tungstato de prata. Os padrões de DRX revelaram a cristalização monofásica de todas as amostras na estrutura ortorrômbica do tungstato de prata e indicaram que estas apresentam ordem estrutural a longa distância. As pequenas variações nos parâmetros de rede e nas coordenadas atômicas, indicam a existência de distorções sobre os clusters de [𝐴𝑔𝑂𝑛] (𝑛 = 2, 4, 6 e 7) e [𝑊𝑂6] e a inserção dos átomos de 𝑁𝑖 na rede cristalina 𝛼 − 𝐴𝑔2𝑊𝑂4. Os dados dos refinamentos de Rietveld também mostraram que os sítios da 𝐴𝑔2 e 𝐴𝑔4 referentes aos clusters [𝐴𝑔𝑂7] e [𝐴𝑔𝑂4], respectivamente, são os mais prováveis para a ocupação dos átomos de 𝑁𝑖. Alterações nos espectros de MR e a detecção de picos referentes a ligação 𝑁𝑖 − 𝑂 nos espectros de IV das soluções sólidas, sugerem a introdução de átomos de 𝑁𝑖 na rede do 𝐴𝑔2𝑊𝑂4. As imagens de MEV revelaram que os íons 𝑁𝑖2+ foram capazes de modificar a morfologia dos microcristais de tungstato de prata, nas condições estudadas. Os espectros de EDX e imagens de mapeamento indicaram que todos os materiais são compostos pelos elementos 𝐴𝑔, 𝑊 e 𝑂, como esperado. Estes também apontaram a presença do elemento 𝑁𝑖 na composição das soluções sólidas. Os valores da 𝐸𝑔𝑎𝑝 estimados por meio dos espectros de UV-vis, sugerem a existência de estados intermediários na região proibida, provenientes de defeitos estruturais. As mudanças nos espectros de FL das amostras indicaram que os átomos de 𝑁𝑖 alteraram o efeito de ordem-desordem a média distância e favoreceram emissões mais energéticas associadas aos defeitos rasos.