Fósforos a base de silicatos de Ca e Mg foram preparados pelo método sol-gel combinado com o processo de sais fundidos. O gel de sílica foi obtido a partir da solução de Na2SiO3 usando soluções de cloretos de európio, disprósio, cálcio e magnésio. Assim, estes cloretos foram homogeneamente distribuídos no gel. O gel obtido foi seco e tratado termicamente a 900°C por 1h para permitir a fusão dos sais presentes. Em seguida o material foi lavado com água até teste negativo para íons Cl- e seco em estufa a 80°C. A redução do európio para Eu2+ foi realizada em um forno sob atmosfera de 5% de H2 e 95% de Ar a 900°C por 3h para obter os fósforos de CaMgSi2O6:Eu2+ e CaMgSi2O6:Eu2+:Dy3+. Nos difratogramas de DRX das amostras, a diopsita foi identificada como fase cristalina principal e quartzo, como a secundária. Micrografias obtidas por MEV (microscopia eletrônica de varredura), das amostras, mostraram morfologia acicular, esférica, folhas e bastonetes das partículas e dos aglomerados . Curva de análise térmica (TGA-DTGA) revelou que a temperatura de cristalização do CaMgSi2O6:Eu2+ é próxima de 765°C. Estudos de espectroscopia de fotoluminescência foram baseados nas transições interconfiguracionais 4fN → 4fN-1 5d do íon Eu2+. O espectro de excitação apresentou banda larga relativa à transição de transferência de carga ligante metal (LMCT) O2- (2p) → Eu3+ na região de 250 nm e bandas finas oriundas das transições 4f → 4f do íon Eu3+ , mostrando a transição 7F0 → 5L6 em 393 nm quando a emissão é monitorada em 583,5 nm. E o espectro de emissão com excitação monitorada em 393 nm apresentou picos finos entre 570 e 750 nm característicos das transições 5D0 → 7 FJ (J = 0 - 5) do íon Eu3+ , indicando que o íon Eu3+ se encontra em um sítio com centro de inversão. Os resultados obtidos indicam que o método desenvolvido é viável na síntese de fóforos, CaMgSi2O6:Eu2+ e CaMgSi2O6:Eu2+:Dy3+ como foi proposto. / Ca and Mg silicates based phosphors were prepared by sol-gel method combined with the molten salts process. The gel of silica was obtained from Na2SiO3 solution by using europium, dysprosium, calcium and magnesium chloride solutions. Therefore, those chlorides were homogenously dispersed into the gel. The obtained gel was dried and heat treated to 900° C for 1h to allow the fusion of the present salts. Then it was water washed until negative test for Cl-, and dried. The reduction of the europium to Eu2+ was performed under atmosphere of 5% of H2 and 95% of Ar to 900° C for 3h, to reach CaMgSi2O6:Eu2+ and CaMgSi2O6:Eu2+:Dy3+ phosphors. Diopside was identified as main crystalline phase and quartz, as secondary phase from XRD (X-ray diffraction) patterns. SEM (scanning electron microscopy) micrographs, of the samples showed needles, spheres, leaves and rods of particles and agglomerates. Thermal analysis (TGA-DTGA) curves revealed that the crystallization temperature of CaMgSi2O6:Eu2+ lies around 765° C. Photoluminescence spectroscopy of the phosphors was studied based on interconfigurational 4fN → 4fN-1 5d transition of Eu2+ ion. The spectra of excitation showed 4fN → 4fN-1 5d transition of Eu2+ ion broad band, related to the ligand to metal charge transfer transition (LMCT) O2- (2p) → Eu3+ in the 250 nm region, when the emission is monitored at 583,5 nm. It also presents the 4f ↔ 4f transitions of Eu3+ ion bands, showing the 7F0 → 5L6 transition at 393 nm. From emission spectra with excitation monitored at 393 nm, it can be observed fine peaks between 570 and 750 nm which are characteristics of 5D0 7FJ (J = 0 - 5) transition of Eu3+ ion, indicating that the Eu3+ ion occupies a site with center of inversion. Finally, the obtained results indicate that the developed method is suitable to synthesize CaMgSi2O6:Eu2+ and CaMgSi2O6:Eu2+:Dy3+ phosphors, as it has been proposed.

Fósforos a base de silicatos de Ca e Mg foram preparados pelo método sol-gel combinado com o processo de sais fundidos. O gel de sílica foi obtido a partir da solução de Na2SiO3 usando soluções de cloretos de európio, disprósio, cálcio e magnésio. Assim, estes cloretos foram homogeneamente distribuídos no gel. O gel obtido foi seco e tratado termicamente a 900°C por 1h para permitir a fusão dos sais presentes. Em seguida o material foi lavado com água até teste negativo para íons Cl- e seco em estufa a 80°C. A redução do európio para Eu2+ foi realizada em um forno sob atmosfera de 5% de H2 e 95% de Ar a 900°C por 3h para obter os fósforos de CaMgSi2O6:Eu2+ e CaMgSi2O6:Eu2+:Dy3+. Nos difratogramas de DRX das amostras, a diopsita foi identificada como fase cristalina principal e quartzo, como a secundária. Micrografias obtidas por MEV (microscopia eletrônica de varredura), das amostras, mostraram morfologia acicular, esférica, folhas e bastonetes das partículas e dos aglomerados . Curva de análise térmica (TGA-DTGA) revelou que a temperatura de cristalização do CaMgSi2O6:Eu2+ é próxima de 765°C. Estudos de espectroscopia de fotoluminescência foram baseados nas transições interconfiguracionais 4fN → 4fN-1 5d do íon Eu2+. O espectro de excitação apresentou banda larga relativa à transição de transferência de carga ligante metal (LMCT) O2- (2p) → Eu3+ na região de 250 nm e bandas finas oriundas das transições 4f → 4f do íon Eu3+ , mostrando a transição 7F0 → 5L6 em 393 nm quando a emissão é monitorada em 583,5 nm. E o espectro de emissão com excitação monitorada em 393 nm apresentou picos finos entre 570 e 750 nm característicos das transições 5D0 → 7 FJ (J = 0 - 5) do íon Eu3+ , indicando que o íon Eu3+ se encontra em um sítio com centro de inversão. Os resultados obtidos indicam que o método desenvolvido é viável na síntese de fóforos, CaMgSi2O6:Eu2+ e CaMgSi2O6:Eu2+:Dy3+ como foi proposto. / Ca and Mg silicates based phosphors were prepared by sol-gel method combined with the molten salts process. The gel of silica was obtained from Na2SiO3 solution by using europium, dysprosium, calcium and magnesium chloride solutions. Therefore, those chlorides were homogenously dispersed into the gel. The obtained gel was dried and heat treated to 900° C for 1h to allow the fusion of the present salts. Then it was water washed until negative test for Cl-, and dried. The reduction of the europium to Eu2+ was performed under atmosphere of 5% of H2 and 95% of Ar to 900° C for 3h, to reach CaMgSi2O6:Eu2+ and CaMgSi2O6:Eu2+:Dy3+ phosphors. Diopside was identified as main crystalline phase and quartz, as secondary phase from XRD (X-ray diffraction) patterns. SEM (scanning electron microscopy) micrographs, of the samples showed needles, spheres, leaves and rods of particles and agglomerates. Thermal analysis (TGA-DTGA) curves revealed that the crystallization temperature of CaMgSi2O6:Eu2+ lies around 765° C. Photoluminescence spectroscopy of the phosphors was studied based on interconfigurational 4fN → 4fN-1 5d transition of Eu2+ ion. The spectra of excitation showed 4fN → 4fN-1 5d transition of Eu2+ ion broad band, related to the ligand to metal charge transfer transition (LMCT) O2- (2p) → Eu3+ in the 250 nm region, when the emission is monitored at 583,5 nm. It also presents the 4f ↔ 4f transitions of Eu3+ ion bands, showing the 7F0 → 5L6 transition at 393 nm. From emission spectra with excitation monitored at 393 nm, it can be observed fine peaks between 570 and 750 nm which are characteristics of 5D0 7FJ (J = 0 - 5) transition of Eu3+ ion, indicating that the Eu3+ ion occupies a site with center of inversion. Finally, the obtained results indicate that the developed method is suitable to synthesize CaMgSi2O6:Eu2+ and CaMgSi2O6:Eu2+:Dy3+ phosphors, as it has been proposed.

Ce travail de thèse porte sur l'étude des verres alumino-silicatés de calcium dopés à l'europium et le processus de leur cristallisation sous forme des vitrocéramiques dans le cadre de la recherche de nouveaux phosphores pour application LED à émission blanche. Nous avons étudié trois échantillons vitreux avec différentes teneurs en silice et avons élaboré des vitrocéramiques cristallisées. La caractérisation des verres et des vitrocéramiques a été réalisée par différentes techniques expérimentales : l'analyse thermique, la diffraction des rayons X et la spectroscopie de diffusion Raman. Les propriétés spectroscopiques de l'ion europium dans les verres et les vitrocéramiques synthétisés ont été étudiées. Le contrôle de la cristallisation des vitrocéramiques GC34 et GC50 par la diffraction des rayons X a permis d'identifier deux phases la mélilite et l'anorthite. Dans le cas de la vitrocéramique GC7, une seule phase alumino-calcique qui est la mayenite est cristallisée majoritairement. L'étude par la spectroscopie de diffusion Raman a permis d'une part, de suivre l'évolution de la cristallisation pendant les traitements thermiques en surface et en profondeur dans l'ensemble des vitrocéramiques. Nous avons montré que le processus de cristallisation a eu lieu en surface des échantillons et correspond typiquement à une nucléation hétérogène. D'autre part, une étude comparative avec des échantillons naturels analogues prise de la base de données RRUFF nous a permis de valider l'ensemble des résultats trouvés. Dans le cas des vitrocéramiques GC34 et GC50, les mesures des spectres d'émission et les durées de vie de l'ion Eu3+ montrent bien son incorporation dans les phases cristallines formées. L'ion Eu3+ tend à occuper seulement les sites Ca2+ (CN= 8) de la mélilite majoritaire dans la vitrocéramique GC34 alors, qu'il tend à s'incorporer dans les sites Ca2+ (CN= 6 et 7) et Ca2+ (CN=8) respectivement, des phases anorthite et mélilite formées dans la vitrocéramique GC50. Ces résultats ont été confirmés par les mesures d'affinement de raies. L'étude des spectres d'émission de l'ion Eu2+ a permis de mettre en évidence une modification de son environnement durant la cristallisation traduite par son incorporation dans les sites Ca2+ après réduction de l'ion Eu3+ pendant les recuits. Dans le cas de la vitrocéramique GC7, les spectres d'émissions et les mesures du déclin de luminescence de l'ion Eu3+ montrent bien que l'ion Eu3+ est incorporé dans la phase mayenite formée. En terme d'application, les mesures des coordonnées trichromatiques suggèrent que la dévitrification des verres semble être une technique efficace permettant d'obtenir de nouveaux matériaux luminophores (LED blanches) à émission intensifiée (cas des vitrocéramiques GC34 et G50) et accordable en modifiant leur composition et l'excitation / This work concerns the study of calcium aluminosilicate glass doped with europium and their process of crystallization as glass-ceramics as part of the search for new phosphors for white LED application. We studied three glass samples with different silica contents and have elaborated crystallized glass-ceramics. Characterization of glasses and glass-ceramics was performed by different experimental techniques: thermal analysis, X-ray diffraction and Raman spectroscopy. The spectroscopic properties of the europium ion in the glass and glass-ceramic synthesized were studied.Control of crystallization of GC34 and GC50 glass-ceramics by X-ray diffraction have been identified two phases, melilite and anorthite. In the case of the GC7 glass-ceramic, a single aluminum calcium phase, mayenite which crystallized predominantly. The study by Raman spectroscopy allowed to follow the evolution of the crystallization during heat treatment in the surface and of glass-ceramics. We have shown that the crystallization process initiate at the surface of the samples and corresponds typically to a heterogeneous nucleation. On the other hand, a comparison with similar natural samples allowed us to validate all the identifications.In the case of GC34 and GC50 glass-ceramics, emission spectra and lifetimes of Eu3+ ion clearly show its incorporation into the new-formed crystalline phases. The Eu3+ ion occupy the Ca2+ sites (CN = 8) in the major mélilite phase of the the GC34 glass-ceramic while, it incorporates the Ca2+ sites (CN = 6 and 7) and Ca2+ (CN = 8) of anorthite and mélilite phases formed in the GC50 glass-ceramic, respectively. These results were confirmed by Fluorescence Line Narrowing (FLN) measurements. The study of emission spectra of the Eu2+ ion allowed highlighting changes during crystallization associated with the reduction of the Eu3+ ions during annealing. In the case of the low silicate GC7 glass-ceramic, emission spectra and lifetimes measurements of the Eu3+ ion show that the Eu3+ ions are incorporated into the mayenite phase. In terms of application, the analyses of the trichromatic coordinates suggest that the glass devitrification appears to be an efficient technique to achieve new white LED phosphor materials with intensified (mainly for GC34 and G50 glass-ceramics) and tunable emission by varying composition and/or excitation

La stratégie la plus utilisée aujourd'hui pour la conception de nouveaux matériaux luminescents est basée sur des méthodes d'essais-erreurs. Cependant, ces méthodes peuvent souvent entraîner une consommation d'argent et de temps. En ce sens, un modèle théorique agissant comme un outil prédictif peut servir comme une stratégie alternative. De tels modèles sont également étudiés et utilisés par des scientifiques du monde entier, mais ils sont pour la plupart difficiles à utiliser. Dans ce travail, deux modèles semi-empiriques conviviaux et faciles à utiliser ont été proposés pour la conception de luminophores intégrés dans le développement de technologies importantes, en particulier dans les éclairages à base de LED et les cellules solaires. Ces modèles sont: 1) le modèle de facteur environnemental (EF) basé sur la théorie diélectrique de la liaison chimique proposée par Philips et 2) le modèle de transfert de charge métal-métal (MMCT) utilisées pour trouver des relations entre les propriétés structurelles d'un matériau et sa luminescence. Le modèle EF a été appliqué à la famille des composés AIBIIPO4 (AI = cation monovalent, BII = cation divalent) dopés à Eu2+. Il était capable d'estimer l'énergie du bord d'excitation et d'identifier les sites de dopage à ± 1000 cm-1. Il peut donc être utilisé pour la conception de nouveaux luminophores appartenant à cette famille. Dans la deuxième partie, les deux modèles ont été utilisés pour identifier la nature de la luminescence dans les oxydes dopés à Bi3+. A cet effet, une méthode combinant les modèles motionnés avec les valeurs de Stokes shift a été trouvé fiable. En outre, la a été jugée utile pour expliquer la modification des propriétés luminescentes de YVO4:Bi3+ sous haute pression. Dans la troisième partie, les deux modèles ont été utilisés pour explorer la luminescence des oxydes dopés à Sb3+ par analogie avec Bi3+. Cependant, les résultats n'étaient pas assez bons pour identifier la nature de la luminescence dans ces matériaux. La raison pourrait être liée à la position décentrée du dopant (Sb3+). / The most used strategy for the design of new luminescent materials today is based on trial-error methods. However, these methods may often result in consummation of money and time. In this sense, a theoretical model acting as a predictive tool can serve as an alternative strategy. Such models are also studied and used by scientists around the world but they are mostly difficult to use. In this work, two friendly and easy to use semi-empirical theoretical models were proposed as a criterion for designing phosphors integrated in the development of important technologies especially in LED-based lightings and solar cells. These models are: 1) the environmental factor model (EF) based on the dielectric theory of chemical bonding proposed by Philips and 2) the metal to metal charge transfer (MMCT) model by Boutinaud that were both used for the purpose of finding relationships between the structural properties of a material and its luminescence. The EF model was applied on the family of AIBIIPO4 (AI= monovalent cation, BII= divalent cation) compounds doped with Eu2+. It was able to estimate the excitation edge energy and to identify the doping sites within uncertainty of ± 1000 cm-1. It can therefore, be used for the design of new phosphors belonging to this family. In a second part, both models were used to identify the nature of luminescence in Bi3+-doped oxides. For this purpose, a method combining the mentioned models along with the values of the Stokes shift was found reliable. In addition, the method was found useful to explain the change in luminescent properties of YVO4:Bi3+ under high pressure. In the third part, the two models were used to explore the luminescence of Sb3+-doped oxides by analogy with Bi3+. However, the results were not good enough to identify the nature of luminescence in these materials. The reason could be related to the off-centered position of the dopant (Sb3+).

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第15670号 / 工博第3328号 / 新制||工||1502(附属図書館) / 28207 / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 田中 勝久, 教授 平尾 一之, 教授 横尾 俊信 / 学位規則第4条第1項該当