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首页> 外文期刊>Zeitschrift fur Anorganische und Allgemeine Chemie >Tantalum cluster in an oxidic matrix - Synthesis and structures of mixed-valence oxotantalates M2-delta Ta15O32 (M = K, Rb (delta = 0); M = Sr (delta = 0.15), Ba (delta = 0.12)) [German]
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Tantalum cluster in an oxidic matrix - Synthesis and structures of mixed-valence oxotantalates M2-delta Ta15O32 (M = K, Rb (delta = 0); M = Sr (delta = 0.15), Ba (delta = 0.12)) [German]

机译：氧化基质中的钽簇-混合价态氧钽酸甲酯M2-δTa15O32（M = K，Rb（δ= 0）; M = Sr（δ= 0.15），Ba（δ= 0.12））的合成和结构[德国]

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摘要

The mixed-valent oxides Sr1.85Ta15O32 (1), Ba1.88Ta15O32 (2), K2Ta15O32 (3), Rb2Ta15O32 (4) were prepared from appropriate mixtures of Ta2O5, tantalum and the corresponding carbonate at 1520-1670 K in sealed tantalum tubes. According to X-ray single crystal structure analyses the oxides crystallize in the space group R (3) over bar, Z = 1. The lattice parameters in the hexagonal setting are a = 777.36(11), c = 3516.2(7) pm for 1, a = 778.87(11), c = 3548.1(7) pm for 2, a=780.7(2), c=3573.1(11)pm for 3, and a=781.90(11), c = 3593.0(7) pm for 4. The oxide ions form a defect dense packing with the layer sequence chhhh. Anti-cuboctahedral sites are completely occupied by the alkali metal cations. The alkaline earth cations occupy 92 to 94% of such sites; they are displaced from the centres. Smaller voids are located in the centres of the cuboctahedral Ta6O12 clusters forming the characteristic structural unit of these low-valent oxotantalates. In case of 3 and 4 the clusters have 13 electrons, in case of 1 and 2 they have close to 15 electrons available for Ta-Ta-bonding. Moreover, the structures of the alkali and alkaline earth metal compounds differ notably with respect to the spectrum of Ta-O and Ta-Ta distances in the Ta3O13 octahedra triples forming another characteristic structural unit for these oxides. Such differences are traced back to distinct local charge balances for the uni- and divalent cations. The oxides 2, 3 are semiconductors with band gaps ranging from 130 to 360 meV. [References: 19]
机译：混合价氧化物Sr1.85Ta15O32（1），Ba1.88Ta15O32（2），K2Ta15O32（3），Rb2Ta15O32（4）是由Ta2O5，钽和相应的碳酸盐的适当混合物在密封的钽管中以1520-1670 K制备的。根据X射线单晶结构，分析在空间棒R（3）上结晶的氧化物，Z =1。六边形设置下的晶格参数为a = 777.36（11），c = 3516.2（7）pm，对于1，对于2，a = 778.87（11），c = 3548.1（7）pm，对于3，a = 780.7（2），c = 3573.1（11）pm，对于3，a = 781.90（11），c = 3593.0（7） pm为4。氧化物离子以层序chhhh形成缺陷密集的堆积。抗立方八面体位点完全被碱金属阳离子占据。碱土金属阳离子占此类位置的92％至94％;他们从中心流离失所。较小的空隙位于立方八面体Ta6O12团簇的中心，形成这些低价氧钽酸钾盐的特征结构单元。在3和4的情况下，簇具有13个电子，在1和2的情况下，它们具有接近15个可用于Ta-Ta键的电子。此外，碱金属和碱土金属化合物的结构在Ta3O13八面体三元组中Ta-O和Ta-Ta距离的光谱方面存在显着差异，形成了这些氧化物的另一特征结构单元。这种差异可追溯到一价和二价阳离子的独特局部电荷平衡。氧化物2、3是带隙在130至360meV范围内的半导体。 [参考：19]

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