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Lanthanum chromite is a perovskite oxide type, which exhibit high mechanical and chemical stability, high electric conductivity for use in SOFC and catalytic activity for the oxidation reaction. However, their optical properties have not yet been studied. The aim of this study was to synthesize lanthanum chromite by the microwave assisted self-combustion method for use as ceramic pigment. The resulting precursor powders were calcined at 800 to 1000 ° C to obtain the perovskite phase and characterized by X-ray diffraction, followed by Rietveld refinement, UV-Visible and colorimetry. The results revealed porous powders, nanometric, and single-phase with orthorhombic perovskite structure. There was few change in the colorimetric parameters, the chromites presented colours with gray tones which became darker in the calcined powder at higher temperatures.

The lanthanum nickelate, LaNiO 3-δ , perovskite catalyst was synthesized by the Pechini process, characterized by X-ray diffraction patterns, iodometric titrations, BET-surface area and scanning electron microscopy. The material obtained was used as catalyst for n-heptane combustion in the temperature range of 350-450ºC under dynamic air atmosphere, in a fixed bed continuous flow reactor. This catalyst shows very good performance in n-heptane combustion.

The lanthanum nickelate, LaNiO 3-δ , perovskite catalyst was synthesized by the Pechini process, characterized by X-ray diffraction patterns, iodometric titrations, BET-surface area and scanning electron microscopy. The material obtained was used as catalyst for n-heptane combustion in the temperature range of 350-450ºC under dynamic air atmosphere, in a fixed bed continuous flow reactor. This catalyst shows very good performance in n-heptane combustion.

ResumoNo presente trabalho estuda-se a síntese, caracterização e propriedades fotoluminescentes de sistemas contendo óxidos de lantânio, cério e níquel. Estes materiais foram preparados pelo método dos precursores poliméricos, calcinados na faixa de temperatura de 300 a 800 o C e então caracterizados por análise CHN, análise termogravimétrica, infravermelho com transformada de Fourier e difração de raios X. Os resultados revelaram a formação de fase cristalina em 800 o C. Os espectros fotoluminescentes dos sistemas desordenados foram registrados a temperatura ambiente. O sistema de lantânio, cério e níquel apresentou forte intensidade fotoluminescente, centrado em 599 nm, quando excitado a 488 nm. Palavras-chave: óxidos de lantânio, cério e níquel, fotoluminescência, precursor polimérico. AbstractThe synthesis, characterization and photoluminescence property of the systems containing lanthanum, cerium and nickel oxides were studied. These materials were prepared by the polymeric precursors, calcined at temperatures ranging from 300 to 800 o C. Afterwards they were characterized by CHN analysis, thermogravimetric analysis, Fourier-transform infrared spectroscopy and Xray diffraction. The results revealed the formation of the crystalline phases at 800 °C. The photoluminescence spectra of disordered systems have been observed at room temperature. The lanthanum, cerium and nickel system presented strong photoluminescence intensity centered at 599 nm when excited to 488 nm.

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