Abstract A lanthanum strontium zirconate pyrochlore material was substituted with Ni, and the effect of calcination temperature on important catalytic properties was evaluated. The introduction of the Ni into the pyrochlore decreased the BET surface as compared to non-Ni containing materials due to enhanced sintering. The presence of Ni dispersed in the precursor material produced oxygen vacancies which improved solid state diffusion of the pyrochlore cations, and lowered the onset of crystallization by almost 100 °C compared to the baseline material without Ni. Furthermore, only a small amount of Ni was found to be soluble in the structure up to 1000 °C, at which point almost no Ni occupies lattice positions in the pyrochlore crystal structure. The Ni was found to exsolve to the surface and grain boundary regions of the pyrochlore and reside on the surface as NiO. Heating to temperatures greater than 800 °C also led to the formation of a La 2 ZrNiO 6 perovskite phase. Surface composition, as measured by XPS, showed a decrease in Ni concentration at the surface as the calcination temperature was increased. This was likely due to the formation of larger Ni particles with increasing temperature, as well as the migration of the Ni into the bulk through the formation of the La 2 ZrNiO 6 phase. Temperature programmed reduction results showed that increasing the calcination temperature resulted in particle growth of the NiO and a weaker interaction with the pyrochlore surface, which made the NiO more reducible at lower temperatures. Multiple reduction-oxidation TPR/TPO cycles showed that the results were not reproducible from cycle-to-cycle for the lowest calcination temperature material (700 °C) due to an amorphous La-Zr-O phase initially present. However, materials calcined at all other temperatures showed an almost identical TPR/TPR profiles after the second cycle.

中文翻译：

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镍取代镧-锶-锆烧绿石的煅烧温度表征

摘要 以镍取代锆酸镧锶烧绿石材料，评价了煅烧温度对重要催化性能的影响。与不含镍的材料相比，由于烧结增强，将 Ni 引入烧绿石中降低了 BET 表面。分散在前体材料中的 Ni 的存在产生了氧空位，这改善了烧绿石阳离子的固态扩散，与没有 Ni 的基线材料相比，结晶的开始时间降低了近 100 °C。此外，发现只有少量 Ni 可溶于高达 1000 °C 的结构中，此时几乎没有 Ni 占据烧绿石晶体结构中的晶格位置。发现 Ni 溶出到烧绿石的表面和晶界区域，并以 NiO 的形式存在于表面。加热到高于 800 °C 的温度也会导致 La 2 ZrNiO 6 钙钛矿相的形成。通过 XPS 测量的表面组成显示，随着煅烧温度的升高，表面的 Ni 浓度降低。这可能是由于随着温度升高形成更大的 Ni 颗粒，以及 Ni 通过 La 2 ZrNiO 6 相的形成迁移到本体中。程序升温还原结果表明，提高煅烧温度会导致 NiO 的颗粒生长和与烧绿石表面的相互作用减弱，这使得 NiO 在较低温度下更容易还原。多次还原-氧化 TPR/TPO 循环表明，由于最初存在无定形 La-Zr-O 相，因此对于最低煅烧温度材料 (700 °C)，结果在循环之间不可重现。然而，在所有其他温度下煅烧的材料在第二次循环后显示出几乎相同的 TPR/TPR 曲线。