Sol–Gel and Solid-State Synthesis and Property Study of La[sub 2−x]Sr[sub x]NiO[sub 4] (x≤0.8)

Abstract

In this study, sol–gel synthesis conditions for the formation of La2−xSrxNiO4 ( x=0 , 0.2, 0.4, 0.6, and 0.8) compounds were investigated. Effects of Sr substitution on A-site on the properties of the compounds were studied using Fourier transform IR spectroscopy, X-ray diffractometry, scanning electron microscopy, and electrical and thermal analyses. A simple sol–gel preparation process was successfully developed at room temperature using water as the solvent in the presence of ethanolamine as the directing agent. The sol–gel synthesis method was effective in yielding higher purity and more homogenous samples than those synthesized via the solid-state reaction method. The addition of Sr helped stabilize the Ruddlesden–Popper structure, and a highly agglomerated morphology of the sintered samples with Sr substitution was observed, resulting in lower density. Sr helped increase conductivity, whereas its effect on thermal expansion was not as pronounced. La1.2Sr0.8NiO4 synthesized via the sol–gel process provided a conductivity of 160 S/cm at 500°C with a coefficient of thermal expansion value of 13×10−6°normalC−1 between 400 and 700°C .

Effect of Sr substituted La2−xSrxNiO4+δ (x = 0, 0.2, 0.4, 0.6, and 0.8) on oxygen stoichiometry and oxygen transport properties

“…The activation energy for D* was found to be 0.60 eV ( 19 and lower than that with no Sr substitution (Ea = 0.85 eV). 11 Although, D* and k* of La 1.2 Sr0. 19,23 However, the k* value do not follow the same trend at 800°C.…”

“…[5][6][7][8] Ruddlesden-Popper structure with the general formula A n+1 MnO 3n+1 (n=1,2,3,…) is a structure that comprised of ABO 3 perovskite layers, alternating with AO rock-salt layers, stacking along the c axis. 4,11 The La 2 NiO 4+δ structure is made up of sheets of (NiO 6 ) corner sharing octahedra, interleaved with La 2 O 2 layers in which the additional oxygen could be localized. Therefore, these oxygen excess materials caught a lot of interest as cathodes for SOFC applications due to their potentially high oxygen transport property.…”

“…La 2 NiO 4+δ and related materials exhibiting Ruddlesden-Popper structure have been proposed as candidates for energy related electrochemical applications because of their excellent transport and electrocatalytic properties. [5][6]8,11,[13][14][15][16] Zhao et al studied the lanthanum deficient compound, La 2−x NiO 4+δ (x = 0, 0.05). 4,11 The La 2 NiO 4+δ structure is made up of sheets of (NiO 6 ) corner sharing octahedra, interleaved with La 2 O 2 layers in which the additional oxygen could be localized.…”

“…However, La 1.9 Sr 0.1 NiO 4+δ appears to be more stable than either of these two materials in terms of thermal expansion behaviour at high temperatures. 11 However, there are still very few reports on the ionic transport in Sr substituted La 2 NiO 4+δ , particularly with Sr substitution content at x > 0.1. For example, Ishikawa et al reported that the electron density in LaSrNiO 4 was almost an order of magnitude larger than that of La 2 NiO 4 .…”

Impact of Oxygen Deficiency on the Electrochemical Performance of K2NiF4‐Type (La1−xSrx)2NiO4−δ Oxygen Electrodes

“…The available literature data show that the electrical conductivity of (La 1Àx Sr x ) 2 NiO 4 AE d ceramics under oxidizing conditions at temperatures below 1000 8Ct ends to increasew ith Sr content in the range 0 < x < 0.5. [1,2,38,41,43,46,47] Skinner and Kilner [6,7] reported that the substitution of 5-10 at %o fL ab yS rd ecreases oxygen tracer diffusion coefficients at 640-840 8Cb ya lmost 1-2 orders of magnitude in correlation with the decreasing concentration of mobile oxygen interstitials. In agreement with that, Li et al [48,49] demonstrated that Sr substitution results in ad ecrease of oxygen permeation fluxes through (La 1Àx Sr x ) 2 NiO 4 AE d (x = 0.05-0.10) ceramic membranes and the oxygen self-diffusion coefficient in these nickelates.…”