Über Oxotantalate der Lanthanide des Formeltyps MTaO4 (M = La – Nd, Sm – Lu)†
Über Oxotantalate der Lanthanide des Formeltyps MTaO4 (M = La – Nd, Sm – Lu)†
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MTaO4 型镧系元素的超氧钽酸盐 (M = La – Nd, Sm – Lu)†
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
T. Schleid
中科院分区：
文献类型：
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作者：
Ingo Hartenbach;Falk Lissner;Tanja Nikelski;Steffen F. Meier;H. Mueller;T. Schleid
关于镧系钽酸盐MTaO_4（M = La-Nd，Sm-Lu）
除了是钽安瓿中固态合成的副产物之外，式MTaO 4的镧系（III）氧代钽酸盐可以容易地通过用氯化钠作为助熔剂烧结镧系倍半氧化物M2 O 3和钽（V）氧化物Ta 2 O 5来制备。在这些条件下，两种结构类型出现取决于M3+阳离子半径。当M = La-Pr时，MTaO_4型钽酸盐晶体属P_（21/c）空间群，晶格常数为a = 762（±1），B = 553（±4），c = 777（±4）pm，β = 101（±1）°，每个晶胞有4个化学式单元。当M = Nd，Sm-Lu时，单斜晶胞尺寸（空间群P2/c）收缩到晶格常数如a = 516（±9），B = 551（±9），c = 534（±9）pm，β = 96.5（±0.3）°，并且仅存在两个分子式单元.这两种结构都显示出八个氧原子的配位球，对于镧系元素三价体，其形状为具有较大镧系元素的结构的扭曲正方形反棱柱（在下文中称为A型）和具有较小镧系元素的结构的三角十二面体（在下文中称为B型）。Ta ~（5+）离子的配位环境对A型结构的MTaO_4为轻微畸变八面体（CN = 6），对B型结构的MTaO_4为严重畸变八面体（CN = 6）。这两种类型之间的差异是由于这些[TaO 6]7−八面体的相互连接。A型MTaO 4结构中八面体通过四个顶点连接形成平行于bc平面的波纹层，而B型MTaO 4结构中八面体共享边缘，沿c轴沿着形成锯齿形链。
About Lanthanide Oxotantalates with the Formula MTaO4 (M = La – Nd, Sm – Lu)
Besides being a by-product of solid state syntheses in tantalum ampoules the lanthanide(III) oxotantalates of the formula MTaO4 can be easily prepared by sintering lanthanide sesquioxide M2O3 and tantalum(V) oxide Ta2O5 with sodium chloride as flux. Under these conditions two structure types emerge depending upon the M3+ cationic radius. For M = La – Pr the MTaO4-type tantalates crystallize in the space group P21/c with lattice constants of a = 762(±1), b = 553(±4), c = 777(±4) pm, β = 101(±1)° and four formula units per unit cell. With M = Nd, Sm – Lu, the monoclinic cell dimensions (space group P2/c) shrink to the lattice constants like a = 516(±9), b = 551(±9), c = 534(±9) pm, β = 96.5(±0.3)° and there are only two formula units present. Both structures show a coordination sphere of eight oxygen atoms for the lanthanide trications shaped as distorted square antiprism for the structure with the larger lanthanides (in the following referred to as A-type) and as trigonal dodecahedron for the structure with the smaller ones (called as B-type in the following). The coordination environment about the Ta5+ cations can be described as a slightly distorted octahedron (CN = 6) for the A-type structure of MTaO4 and a heavily distorted one (CN = 6) for the B-type. The difference between the two types results from the interconnection of these [TaO6]7− octahedra. Whereas they are connected via four vertices to form corrugated layers according to parallel the bc-plane in the A-type, the octahedra of the B-type MTaO4 structure share edges to built up zig-zag chains along the c axis.