Synthesis and characterization of a nano-scaled barium cerate perovskite powder using starch as polymerization agent

Abstract

Synthesis and characterization of a nanoscaled barium cerate perovskite powder using starch as polymerization agent. Solid State Ionics, Elsevier, 2011, 203 (1), pp.Abstract. The preparation of nano-sized BaCeO 3 powder using starch as a polymerization agent is described herein. Phase evolution during the decomposition process of a (BaCe)-gel was monitored by XRD. A phase-pure nano-sized BaCeO 3 powder was obtained after calcining of the (BaCe)-gel at 920 °C. The resulting powder has a specific surface area of 15.4 m 2 /g. TEM investigations reveal particles mainly in the size range of 30 to 65 nm. The shrinkage and sintering behaviour of resulting powder compacts were studied in comparison to a coarse-grained mixed-oxide BaCeO 3 powder (S BET = 2.1 m 2 /g). Dilatometric measurements show that the beginning of shrinkage of compacts from the nano-sized powder 2 is downshifted by 300 °C compared to mixed-oxide powder. Compacts from the nano-sized powder reach a relative density of 91 % after sintering at 1450 °C for 10 h.

Novel composite solid state electrolytes on the base of BaCeO3 and CeO2 for intermediate temperature electrochemical devices

“…The significant change in the weight (6.9 wt.% in the temperature interval 400e650 C) is the result of the oxidation of organic particles and the subsequent removal of CO 2 , N 2 and H 2 O [22]. The final stage of mass loss, starting at 800 C is related with the decomposition of barium carbonate [57], which is, apparently, an intermediate substance in the following scheme of transformation: BaðNO 3 Þ 2 /BaCO 3 /}BaO}/BaCeO 3 . The small endothermic reflex at 830 C is connected with a phase transition of barium carbonate from orthorhombic (g-BaCO 3 , space group Pmcn) to tetragonal structure (b-BaCO 3 , space group R3m) [58,59].…”

Síntese do cerato de bário pelo método de complexação combinando EDTA-citrato e avaliação catalítica na oxidação do monóxido de carbono testada em reator de leito fixo

“…Segundo a literatura, é comum encontrar a presença de fases secundárias como carbonato de bário e óxido de cério quando a calcinação é realizada em temperatura inferior a 1100 °C [17]. Através do refinamento de Rietveld foi constatado que o material BaCeO 3 apresentou sistema cristalino do tipo ortorrômbico com grupo espacial Pmcn, concordante com a literatura [14,[17][18][19][20][21]. Quando a perovskita BaCeO 3 foi sintetizada a partir do método de complexação combinando EDTA-citrato e nas condições experimentais aqui impostas, o tamanho médio de cristalito foi de 133,2 nm, com densidade de 3,38 g.cm −3 e volume de célula unitária igual a 347,89 nm 3 .…”

“…A Tabela II apresenta os parâmetros de rede da perovskita BaCeO 3 e do carbonato de bário (BaCO 3 ) obtidos a partir do difratograma e do refinamento Rietveld. Os parâmetros de rede, volume de célula unitária e densidade das fases demonstram que os resultados obtidos são coerentes com os encontrados na literatura [14,[18][19][20][21] micrografias mostradas na Fig. 3 observa-se a presença de um conjunto de aglomerados com formato esféricos irregulares e tamanhos distintos.…”