摘要: 本研究采用固相反应法合成了通式为 BaLnCo₂O_6–δ 的成分复杂的钴酸盐,其中 Ln 位点包含三到八种不同的镧系元素。熵指标分析和构型熵计算表明,这些钴酸盐属于中熵氧化物,且均以四方双钙钛矿结构结晶,空间群为 P4/mmm。它们的晶胞参数由平均离子半径控制,而非构型熵控制。另一方面,它们的氧非化学计量始终高于低熵双钙钛矿钴酸盐的。在本研究条件下,所有材料的总电导率均远高于 50 S/cm,尤其是在 300°C 时,BaLa_1/3Nd_1/3Gd_1/3Co₂O_6–δ 的电导率峰值达到 1487 S/cm。此外,研究结果表明,电导率随取代的镧系元素数量的增加而降低。

Abstract: In this study, compositionally complex cobaltites with the general formula BaLnCo₂O_6−δ with three to eight different lanthanides at the Ln-site were synthesized using the solid-state reaction method and studied. Analysis of entropy metrics and configurational entropy calculations indicated that these compounds are medium entropy oxides. All of these crystallize as tetragonal double perovskites from the space group P4/mmm. The unit cell parameters are controlled by the average ionic radius, not the configurational entropy. On the other hand, the oxygen non-stoichiometry is consistently higher than in the case of low entropy double perovskite cobaltites. The total electrical conductivity of all materials in studied conditions is well above 50 S/cm, peaking at 1487 S/cm for BaLa_1/3Nd_1/3Gd_1/3Co₂O_6−δ at 300°C. The electrical conductivity decreases with the number of substituents.