High-temperature synthesis and structures of perovskite and n=1 Ruddlesden-Popper tantalum oxynitrides
High-temperature synthesis and structures of perovskite and n=1 Ruddlesden-Popper tantalum oxynitrides
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DOI：
10.1021/cm011738y
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发表时间：
2002-06-01
影响因子：
8.6
通讯作者：
Rosseinsky, MJ
中科院分区：
文献类型：
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作者：
Clarke, SJ;Hardstone, KA;Rosseinsky, MJ
先前通过使氧化物前体与氨反应制备的钙钛矿和K2 NiF 4结构的第5族氮氧化物SrTaO 2N、BaTaO 2N、Sr 2 TaO 3 N和Ba 2 TaO 3 N也可以通过适当的碱土金属氧化物与TaON之间在1500 ℃下在1atm纯氮气下反应几小时来制备。氮气气氛对于防止Ta-V还原至关重要，感应加热方法确保样品上方的氮气气氛保持不含氧气或水。SrTaO_2 N的晶体尺寸为I_4/mcm，a = 5.694 × 11（7）埃，B = 8.0658（2）埃，Z = 4。氧化物和氮化物阴离子几乎是完全无序的，如在900-1000 ℃下使用氨通过纯氧化物前体的氮化制备材料时所观察到的，但与在矿化剂辅助下进行这种氮化时观察到的完全O/N顺序形成对比。首次报道了Ba_2TaO_3N的详细结构：该化合物为K_2NiF_4型结构，空间群为I_4/mmm，O/N全序。其中a = 4.115 08（3）埃，c = 13.3778（l）埃，Z = 2，与锶类似物（Sr 2 TaO 3 N：I4/mmm，a = 4.038 99（4）c = 12.6007（3）埃，Z = 2）是同构的。O/N无序在钙钛矿结构氮氧化物中是有利的，但在层状K2 NiF 4结构材料中O/N有序是标准的，有序方案由不同电负性的阳离子之间的竞争决定。
The perovskite- and K2NiF4-structure group 5 oxynitrides SrTaO2N, BaTaO2N, Sr2TaO3N, and Ba2TaO3N, previously prepared by reacting oxide precursors with ammonia, may also be prepared by the reaction between the appropriate alkaline earth oxide and TaON at 1500 degreesC under 1 atm of pure nitrogen gas for a few hours. The nitrogen atmosphere is essential to prevent reduction of Ta-V, and the method of inductive heating ensures that the nitrogen atmosphere above the sample is maintained free of oxygen or water. SrTaO2N crystallizes in I4/mcm with a = 5.694 11(7) Angstrom, b = 8.0658(2) Angstrom, and Z = 4. The oxide and nitride anions are almost completely disordered, as observed when the material is made by nitridation of a pure oxide precursor using ammonia at 900-1000 degreesC, but contrasting with the full O/N order observed when such nitridation is mineralizer assisted. The detailed structure of Ba2TaO3N is reported for the first time: this compound adopts the K2NiF4 type structure with full O/N order in space group I4/mmm. with a = 4.115 08(3) Angstrom, c = 13.3778(l) Angstrom, and Z = 2 and is isostructural with the strontium analogue (Sr2TaO3N: I4/mmm, a = 4.038 99(4) c = 12.6007(3) Angstrom and Z = 2). O/N disorder is favored in perovskite-structure oxynitrides, but in layered K2NiF4-structure materials O/N ordering is the norm, with the ordering scheme dictated by the competition between cations of differing electronegativity for the anions.