Sol-gel synthesis of lanthanum chromite powder

Bilger, S.; Blab, Gerhard A.; Förthmann, R.

doi:10.1016/s0955-2219(96)00182-3

Cited by 38 publications

(16 citation statements)

References 12 publications

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“…6). These results are similar to those found for fine Srdoped lanthanum chromite powders, in which excessive grain growth was further limited by the SPS process (9). However, the present results showed that a marked growth of a few grains occurred in the sample of La 0.8 Ca 0.2 CrO 3 sintered at 1500°C (Fig.…”

Section: Sintering Of Lasupporting

confidence: 91%

“…The maximum densification obtained by conventional sintering was of 97.71% of the theoretical density for the specimen CS4 in Table 2, and the average grain size measured on this sample was 6 µm. Figure 7 shows typical microstructural aspects of La 0.9 Ca 0.1 CrO 3 and La 0.8 Ca 0.2 CrO 3 samples fired in air at 1400°C for 5 h. The results showed that even under conventional firing conditions, the LCC powders exhibited good sinterability in air atmosphere at lower temperatures (1400°C) when compared with that reported for the sintering of Sr-doped lanthanum chromite powders (1600°C) (9). The differences in the grain size observed in the SPS and the conventionally fired specimens are mainly associated with the use of a relatively lower sintering temperature and shorter sintering time, mainly in the case of the SPS process (9,14).…”

Section: Sintering Of Lamentioning

confidence: 89%

“…The preparation of lanthanum chromite fine powders has been recently carried out by using chemical methods such as sol-gel (8), coprecipitation (9), hydrazine (10) and complex solution synthesis (11). These processing techniques are likely to be useful for the synthesis of fine alkaline earth (Ca or Sr)-doped lanthanum chromite powders at relatively low temperatures (700-800ºC).…”

Section: Introductionmentioning

confidence: 99%

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Sinterización por plasma de particulas ultrafinas de cromita de lantano dopado con clacio obtenidas por síntesis hidrotermal

Rendón-Ángeles¹,

Rivas-Vázquez²,

Pech-Canul³

et al. 2006

Bol. Soc. Esp. Ceram. Vidr.

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Lanthanum chromite nano-particles, with a composition of La 0.9 Ca 0.1 CrO 3 and La 0.8 Ca 0.2 CrO 3 , were produced by 1 h of hydrothermal reaction at 400 and 425°C respectively. The sintering of the powders was conducted using a spark plasma apparatus over the temperature range 1300-1550ºC for 1 min with a constant loading pressure of 45 MPa. Additional sintering experiments using conventional firing were carried out for comparison. Fully densified (98 % r.d.) lanthanum chromite pellets with fine equiaxial grains 2.3 µm in size were obtained using the SPS (spark plasma sintering) method. In contrast, a maximum relative density of 97 % was produced using La 0.8 Ca 0.2 CrO 3 sintered conventionally at 1400ºC for 300 min, and the average grain size of the resulting sintered sample was 6 µm. Sinterización por plasma de particulas ultrafinas de cromita de lantano dopado con clacio obtenidas por síntesis hidrotermalPartículas ultrafinas de cromita de lantano, con una composición de La 0.9 Ca 0.1 CrO 3 y La 0.8 Ca 0.2 CrO 3, se obtuvieron después de 1 hora de síntesis hidrotermal a las temperaturas de 400 y 425°C respectivamente. Los compuestos obtenidos, con un tamaño de partícula de ~ 200 nm, se caracterizaron utilizando las técnicas de DRX, MEB y MET. La sinterización de estos polvos se efectuó en un equipo de chispa de plasma en el rango de temperatura de 1300-1500°C durante 1 min, y a una presión de compactación de 45 MPa. Ambos polvos también se sinterizaron siguiendo un tratamiento térmico convencional, en aire, con el propósito de comparar ambos métodos de sinterización. Las muestras de cromita de lantano sinterizadas por plasma presentaban una densidad relativa del 98 % (ρ/ρ t ); y una microestructura monofásica con granos equaxiales con un tamaño medio de grano menor de 2.3 µm. En contraste, la composición La 0.8 Ca 0.2 CrO 3, sinterizada a 1400°C/300 min, por métodos convencionales alcanzó una densidad relativa máxima del 97 % y su microestructura estaba formada por una sola fase con un tamaño medio de grano de 6 µm.

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Section: Sintering Of Lasupporting

confidence: 91%

Section: Sintering Of Lamentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Sinterización por plasma de particulas ultrafinas de cromita de lantano dopado con clacio obtenidas por síntesis hidrotermal

Rendón-Ángeles¹,

Rivas-Vázquez²,

Pech-Canul³

et al. 2006

Bol. Soc. Esp. Ceram. Vidr.

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“…582 and 900 °C in coincidence with the observation of a relatively large exothermic peak, which shows the formation of a crystalline phase oxide. This process most likely corresponds mainly to an oxygen loss resulting in the final generation of the perovskite phase [6][7][8] .…”

Section: Influence Of Calcination Temperature On Crystallization and mentioning

confidence: 99%

Effect of calcination temperature and reaction conditions on methane partial oxidation using lanthanum-based perovskite as oxygen donor

Dai

Chen

et al. 2008

Journal of Rare Earths

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Abstract:We investigated the effect of calcination temperature, reaction temperature, and different amounts of replenished lattice oxygen on the partial oxidation of methane (POM) to synthesis gas using perovskite-type LaFeO 3 oxide as oxygen donor instead of gaseous oxygen, which was prepared by the sol-gel method, and the oxides were characterized by XRD, TG/DTA, and BET. The results indicated that the particle size increased with the calcination temperature increasing, while BET and CH 4 conversion declined with the calcination temperature increasing using LaFeO 3 oxide as oxygen donor in the absence of gaseous oxygen. CO selectivity remained at a high level such as above 92%, and increased slightly as the calcination temperature increased. Exposure of LaFeO 3 oxides to methane atmosphere enhanced the oxygen migration of in the bulk with time online owing to the loss of lattice oxygen and reduction of the oxidative stated Fe ion simultaneously. The high reaction temperature was favorable to the migration of oxygen species from the bulk toward the surface for the synthesis gas production with high CO selectivity. The product distribution and evolution for POM by sequential redox reaction was determined by amounts of replenished lattice oxygen with gaseous oxygen. The optimal process should decline the total oxidation of methane, and increase the selectivity of partial oxidation of methane.Keywords: perovskite LaFeO 3 ; lattice oxygen; synthesis gas; redox reaction; rare earths Renewed interest in methane conversion to synthesis gas, which can be used to produce a variety of chemicals by the Fischer-Tropsch and methanol synthesis, has arisen. Currently, large-scale industrial route for synthesis gas production was based on steam reforming of methane, which was a capital-and energy-intensive process owing to the highly endothermic nature of the reaction and also a large H 2 /CO ratio. The catalytic partial oxidation (CPO) offered the greatest potential for an efficient and economical conversion of methane to synthesis gas, owing to the high selectivity and suitable H 2 /CO ratio, but the Ni-based catalyst exhibited a rapid deactivation because of carbon deposition that has been reported [1] . Recently, a novel method for synthesis gas production by the direct use of lattice oxygen of perovskite has been proposed by our group [2][3][4] . This new route was superior to general partial oxidation of methane (POM) in stability (resistance to carbonaceous deposition), safety (avoiding effectively the accidental explosion), easy operation and optimization, and low cost (making use of air not oxygen) [4] . The present study aimed to explore the effect of calcination temperature and reaction temperature on catalytic activity for POM over perovskite-type LaFeO 3 oxide using lattice oxygen, and the product distribution was investigated by controlling the amount of replenished lattice oxygen with gaseous oxygen.

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“…A obtenção do cromito de lantânio pela rota sol-gel pode ser feita utilizando-se como materiais de partida os respectivos cloretos metálicos dissolvidos em metanol, precipitados com cloreto de amônio e, estabilizados pela adição de ácido hidroclórico e, do mesmo modo que a síntese por coprecipitação, o material obtido necessita ser calcinado [94,95].…”

Section: Síntese Do Cromito De Lantâniounclassified

Cromito de lantânio: material para interconectores de células a combustível de óxido sólido - uma revisão

2015

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INTRODUÇÃOMaterial sintético de grande importância tecnológica, o cromito de lantânio ainda se destaca como o principal material capaz de conduzir eletricidade em altas temperaturas suportando diferentes tipos de atmosferas frente a materiais como os aços inoxidáveis. Neste trabalho são revisadas as características, as propriedades, as possíveis aplicações e o comportamento durante o processamento do cromito de lantânio e de composições com diferentes tipos e teores de elementos dopantes. Estrutura cristalinaO LaCrO 3 apresenta uma estrutura cristalina do tipo perovskita, sendo considerado como pseudo-perovskita ou perovskita distorcida, por não ser perfeitamente cúbica como normalmente ocorre nas demais perovskitas da família ABO 3 [1]. Formando-se a partir de 650 °C, o LaCrO 3 apresenta célula unitária do tipo ortorrômbica (Pnma), ocorrendo uma transformação alotrópica para a estrutura romboédrica (R3c) durante o aquecimento no intervalo de temperatura entre 240 e 280 °C, tendo como consequência redução no volume do retículo, principalmente devido à redução de tamanho no octaedro CrO 6 . [2,3]. Trabalhos existentes [4] sugerem que esta estrutura permanece estável até a temperatura aproximada de 1800 °C, onde ocorre a transformação da estrutura romboédrica para a cúbica (Pm-3m) [5,6] ) é um material cerâmico sintético, que apresenta como principais características boa condutividade elétrica em altas temperaturas (> 800 °C), estabilidade química e física em atmosferas oxidantes e redutoras e, significativa atividade catalítica quando na forma de pós. Estas características o tornam atrativo para diversas aplicações de interesse tecnológico, como catalisadores, resistências para fornos de alta temperatura e geração de energia elétrica, sendo que nesse campo é potencialmente o material mais adequado para utilização como interconector em células a combustível de óxido sólido (Solid Oxide Fuel Cell -SOFC). As características intrínsecas, propriedades e técnicas de processamento do cromito de lantânio são consideradas neste trabalho por meio de uma revisão dos principais estudos relatados ao longo dos últimos 40 anos. Palavras-chave: cromito de lantânio, SOFC, revisão. AbstractThe lanthanum chromite (LaCrO 3 ) is a synthetic ceramic material, which has as main characteristics of good electrical conductivity at high temperatures (> 800 °C), physical and chemical stability in oxidizing and reducing atmospheres, and a significant catalytic activity when used as powder. These features make it attractive for various technological applications such as catalysts, resistance to high temperature furnaces and electric power generation, and this field is potentially the most appropriate material for use as interconnector in Solid Oxide Fuel Cells (SOFC). The intrinsic characteristics, properties and processing of lanthanum chromite are detailed in this paper through a review of major studies reported over the past 40 years.

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Sol-gel synthesis of lanthanum chromite powder

Cited by 38 publications

References 12 publications

Sinterización por plasma de particulas ultrafinas de cromita de lantano dopado con clacio obtenidas por síntesis hidrotermal

Sinterización por plasma de particulas ultrafinas de cromita de lantano dopado con clacio obtenidas por síntesis hidrotermal

Effect of calcination temperature and reaction conditions on methane partial oxidation using lanthanum-based perovskite as oxygen donor

Cromito de lantânio: material para interconectores de células a combustível de óxido sólido - uma revisão

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