Non‐stoichiometric La(1 − x)NiO(3 − δ) perovskites produced by combustion synthesis

Abstract

La (12x) NiO (32d) perovskites present high metallic conductivity and Pauli-paramagnetism, and could be used as electrodes in electrochemical devices such as SOFCs, PEMFCs and MCFCs. Additionally, due to its s* conducting band, this material shows a very high electrocatalytic activity, particularly in oxygen reduction processes, with an ef®ciency comparable to that of platinum. This work describes the combustion synthesis of La (12x) NiO (32d) perovskite powders (x~0 and 0.1) from mixtures of La(NO 3 ) 3 ?6H 2 O and Ni(NO 3 ) 2 ?6H 2 O as cation precursors, and urea as fuel. The as-prepared combustion product, characterized by XRD, DTA/TG, SEM/TEM, BET and dilatometry (after compaction), shows a much higher speci®c surface area than powders obtained via alternative routes and contains La 2 NiO 4 with a typical K 2 NiF 4 -type structure, together with small amounts of NiO. The usual subsequent heat treatments for 1 to 12 h at successively higher temperatures showed that full conversion to La (12x) NiO (32d) can be readily achieved in air at 750 ³C and that the perovskite, after the 12 h heat treatment, remains stable up to 1100 ³C. These results show that the combustion technique is a better and much simpler route to the synthesis of perovskite powders.

CGO20–CuO composites synthesized by the combustion method and characterized by H2-TPR

“…( According to the literature [12,13,18], the temperature reached locally during combustion is higher than 800ºC, a temperature that allows composite formation. Using stoichiometric molar compositions of the mixtures, CGO-CuO powders composites were produced as noted in the reaction above.…”

“…Nevertheless, in spite 3 of the quality of the powders produced and although powder synthesis can be achieved at low temperature, many solution processes are complicated and lengthy procedures, which limits their applicability. Among other methods wet chemical combustion synthesis (using fuels such as urea, glycine, sucrose, etc) has been employed to obtain multicomponent ceramic oxides [11][12][13], phosphates [14], alloys [15,16], etc. In some cases, this technique produces fine, homogeneous and crystalline powders just in a single synthesis step, reducing preparation time and avoiding the need for additional steps, which can affect and modify the behaviour of the materials [13].…”

“…Among other methods wet chemical combustion synthesis (using fuels such as urea, glycine, sucrose, etc) has been employed to obtain multicomponent ceramic oxides [11][12][13], phosphates [14], alloys [15,16], etc. In some cases, this technique produces fine, homogeneous and crystalline powders just in a single synthesis step, reducing preparation time and avoiding the need for additional steps, which can affect and modify the behaviour of the materials [13]. The basis of the combustion synthesis technique comes from thermochemical concepts used in the field of propellants and explosives [17].…”

Crystal structure, energy transfer mechanism and tunable luminescence in Ce3+/Dy3+ co-activated Ca20Mg3Al26Si3O68 nanophosphors

“…The solution combustion process is favorable for obtaining pure and cost effective nano-sized high-quality oxide powders in a short time [17,18].The process involved the exothermic reaction initiated by metal nitrates (oxidizer) and an organic fuel (reductant).The constituent raw materials used were Ca (NO 3 Glycine (C 2 H 5 NO 2 , 4 99%) was employed as an organic combustion fuel. The stoichiometric amount of the starting materials were weighed and agitated in a beaker with minimum amount of distilled water using magnetic stirrer for 8-10 h to prepare homogeneous solutions.…”

Powder morphology modification and sinterability improvement of Ce0.8Sm0.2O1.9 derived from solution combustion process

“…Combustion synthesis has gained reputations as a simple and speedy route to produce fine complex-oxide powders [23]. Doped-ceria electrolytes have been prepared by combustion synthesis utilizing various fuels [15,24,25].…”