Structural and Spectroscopic Study of a Novel Erbium Titanate Pink Pigment Prepared by Sol−Gel Methodology

Martos, Mónica; Julián‐López, Beatriz; Cordoncillo, Eloísa; Escribano, P.

doi:10.1021/jp077369w

Cited by 45 publications

(24 citation statements)

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“…Among many methods, sol-gel synthesis is particularly promising for production of materials without the need of high-temperature calcination that influence the final properties of the product. [26,27] Concerning these structures, the present study is aimed to obtain cerium titanate compounds as alternative colouring materials to substitute the highly toxic lead, cadmium, chromium and nickel pigments, commonly used in the ceramic industry. This work stresses in the synthetic methodologies (sol-gel route) which allow to obtain mixed oxides with Ti(IV)/Ce(III), Ti(IV)/Ce(IV) or Ti(IV)/Ce(III)-Ce(IV) species.…”

Section: +mentioning

confidence: 99%

Sol–Gel Synthesis of Tunable Cerium Titanate Materials

et al. 2008

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Cerium titanate structures present a high technological interest because of their optical and catalytic properties. This work reports the synthesis of these materials by a sol–gel methodology that allows mixed oxides with TiIV/CeIII, TiIV/CeIV or TiIV/CeIII–CeIV species to be obtained. Crystallization of CeO2–TiO2 mixed oxides and Ce2Ti2O7 pyrochlore phase was corroborated by XRD and Raman spectroscopy. Magnetic and EPR measurements were performed in order to clarify the oxidation state of the cerium ions in the system as a result of the easy oxidation of CeIII. The firing atmosphere is crucial for the CeIII/CeIV ratio, which is responsible for the different structure, but it also affects the colouration (yellow, green, brown). This methodology offers the possibility to modulate the Ce3+/Ce4+ content and particle sizes providing more ecological coloured pigments based on rare earth elements that could be interesting materials for advanced applications in catalysis.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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Section: +mentioning

confidence: 99%

Sol–Gel Synthesis of Tunable Cerium Titanate Materials

et al. 2008

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“…However, this is not the only possibility: they have been observed in processes of phase transformation from fluorite to pyrochlore. [19] In the erbia-zirconia system, the ratio of Er(III) and Zr(IV) radii is in the limit of stability between both structures. Then, other techniques such as XRD, HRTEM and Raman experiments will be necessary to clarify this point.…”

Section: Resultsmentioning

confidence: 99%

Key insights on the structural characterization of textured Er2O3–ZrO2 nano-oxides prepared by a surfactant-free solvothermal route

Julián‐López

Luz

Gonell

et al. 2012

Journal of Alloys and Compounds

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Keywords: structural resolution / Er 2 O 3 -ZrO 2 / HRTEM / fluorite / solvothermal route Zirconia-mixed oxides can exhibit cubic fluorite and pyrochlore structure. Their discrimination is not easy in nanooxides with a crystal size close to that of a few unit cells. In this work, High Resolution Transmission Electron Microscopy (HRTEM) has been employed to provide key insights on the structural characterization of a nanometric and porous mixed Er 2 O 3 -ZrO 2 oxide. The material was prepared by a simple template-free solvothermal route that provided nanocrystalline powders at low temperature (170 ºC) with spherical morphology, and high surface area (280 m 2 /g). The porosity was mainly originated from the assembling of organic complexing agents used in the synthesis to limit the crystal growth and to control hydrolysis and condensation reaction rates. The samples were characterized by thermal analysis, X-ray Diffraction, Scanning Electron Microscopy and N 2 adsorption measurements.A detailed study by HRTEM was conducted on microtomed samples. It was observed that the material was made of nanocrystals packed into spherical agglomerates. HRTEM simulations indicated that it is not possible to identify the pyrochlore phase in nanoparticles with diameter below 2 nm. In our samples, the analysis of the HRTEM lattice images by means of Fast Fourier Transform (FFT) techniques revealed well defined spots that can be assigned to different planes of a cubic fluorite-type phase, even in the raw material. Raman spectroscopy was also a powerful technique to elucidate the crystalline phase of the materials with the smallest nanoparticles. HREM and Raman results evidenced that the material is constituted, irrespective of the temperature of the final calcination step, by an ensemble of randomly oriented nanocrystals with fluorite structure. This study opens new perspectives for the design of synthetic approaches to prepare nanooxides (fluorites and pyrochlores) and the analysis of their crystalline structure.____________ [a]

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“…1, scan 5 As the next step, the pyrochlore-like Ln 2 TiO 5 (Ln = Er-Yb) were heated to 540 or 840 • C, held there for 2 h and then quenched in liquid nitrogen. These temperatures were selected based on earlier data on relaxation processes related to oxygen vacancies in the range 500-600 • C and the high oxygen mobility between 700 and 950 • C due to the ordering transition in the Ln 2+x Ti 2−x O 7−ı (Ln = Er; x = 0, 0.096) pyrochlores [6,17]. The corresponding XRD patterns are displayed in Fig.…”

Section: Resultsmentioning

confidence: 99%