Phase Equilibria and Crystal Structures of Mixed Oxides in the La-Mn-Ni-O System

Abstract

The phase equilibria and crystal structures of mixed oxides in the ternary system La 2 O 3 -Mn 3 O 4 -NiO are studied at 1100 ° C in air. The projection of the La-Mn-Ni-O phase diagram at 1100 ° C and = 0.21 × 10 5 Pa onto the metal-composition triangle is found to comprise 12 phase fields. The lattice parameters of La 2 NiO 4 (sp. gr. I 4/ mmm ), La 3 Ni 2 O 7 (sp. gr. Cmcm ), La 4 Ni 3 O 10 (sp. gr. Cmca ), and La 1 + x Mn 1 -x -y Ni y O 3 solid solutions (sp. gr. Pnma , -0.04 ≤ x ≤ 0.05, 0 ≤ y ≤ 0.4) are determined. The composition stability limits of La 4 Ni 3 -y Mn y O 10 solid solutions are 0 < y ≤ 0.05. With increasing Ni concentration in La 1 + x Mn 1 -x -y Ni y O 3 , the metal nonstoichiometry decreases from -0.04 ≤ x ≤ 0.05 at y = 0 to x = 0 at y = 0.4. p O 2

Reversible perovskite electrocatalysts for oxygen reduction/oxygen evolution

“…The LaMnNiO 3 (B-site substituted) system has been studied extensively for other purposes including the magnetic properties of the materials 18–20. Demina et al 21 synthesised a number of compositions across the entire ternary composition space and developed a structural phase diagram. ORR catalytic activity is reported in the alkali environment for the LaNi 0.5 Mn 0.5 O 3– δ perovskite: LaNi 0.5 Mn 0.5 O 3– δ exhibits the largest current density and lowest overpotential in the series of LaNi 0.5 M 0.5 O 3– δ perovskites (M = Ni, Co, Fe, Mn, and Cr) 3,22,23.…”

Effect of Electron Doping on the Crystal Structure and Physical Properties of an n = 3 Ruddlesden–Popper Compound La4Ni3O10

“…Further oxidation may occur by intercalated O anions in the rock-salt layers, whereas reduction gives random or ordered O vacancies and may result in an unusually low average oxidation state (+1.33 in La 4 Ni 3 O 8 ). , For these RP n compounds, the physical properties are closely linked to their layer-like structure and dimensionality effects. − A large number of phenomena may occur at low temperatures, like electronic and magnetic transitions, colossal magnetoresistance, and long-range magnetic order. − To expand our insights, we currently explore the effect of substitution of nonmagnetic Al 3+ into the Ni sublattices of La 4 Ni 3 O 10 . In general, the incorporation of chemical substitutions into La 4 Ni 3 O 10 is challenging, whether being substituted at the lanthanum sites with alkaline-earth cations or the Ni sites by transition-metal cations such as Mn, Co, and Cu. ,− Correspondingly, attention must be paid to avoid partial phase decomposition.…”

Preparation of La2NiMnO6 Double-perovskite Ceramics by Plasma Activated Sintering

“…Key words: La 2 NiMnO 6 ceramics; plasma activated sintering; sintering temperature; sintering pressure; dielectric property 双钙钛矿化合物比传统钙钛矿化合物具有更加 丰富的组成变化和更加优越的物理性能, 因而存在 较大的研究价值和应用潜力。截至目前, 人们已制 备了超过 300 种的双钙钛矿化合物 [1][2][3] 。La 2 NiMnO 6 (简称 LNMO)作为一种典型的双钙钛矿化合物, 是 第一个被发现的铁磁绝缘体, 并且具有接近室温的 铁磁居里温度, 以及巨介电效应和巨磁阻效应等 [1][2][3] , 因此得到科研工作者越来越广泛的关注。目前, 制 备 LNMO 陶瓷主要采用常压烧结方法 [4][5][6][7] , 虽然常 压烧结具有生产成本低、设备工艺简单等优点, 但 存 在 烧 结 温 度 过 高 (1000~1550 ℃ ) 、 工 艺 周 期 长 (2~20 h), 且烧结体致密性差、孔洞多等缺点 [4][5][6][7] , 这 在一定程度上降低了 LNMO 陶瓷的性能。Li 等 [5] 采用常压烧结, 在 1000 ℃-2 h 烧结得到的 LNMO 陶 瓷中, 孔洞较多; Barbosa 等 [6] 在 1300 ℃下反复多次 常压烧结得到的 LNMO 陶瓷, 耗时过长(>20 h), 致 密度却只有 64%~69%; Chen 等 [7] 虽然制备得到了致 密度较高(~95%)的 LNMO 陶瓷, 但其烧结温度却很 高(1550 ℃-4 h)。 等离子体活化烧结(Plasma Activated Sintering, PAS)是一种在电场、应力场和温度场耦合作用下实 现粉体快速致密化的活化烧结技术 [8][9] 。它集等离子 体活化、压力、电阻加热为一体, 与常压烧结相比, 有利于降低粉末的烧结温度, 而且具有升温速率快 (100~200 ℃/min)、保温时间短(5~20 min)等优势, 可以有效抑制晶粒长大, 从而广泛应用于金属、陶 瓷、复合材料以及功能材料的制备 [10][11][12][13][14][15][16] 。但截至目 前, 有关利用 PAS 制备 LNMO 陶瓷的相关研究, 国 内外还未见报道。 为此, 针对常压烧结制备 LNMO 陶瓷存在的致 密度低、工艺周期长等问题 [5][6][7][17][18][19] [20][21][22][23][24][25]…”