Structural Chemical Studies of Gadolinium-and Erbium Compounds by Moessbauer Spectroscopy

镧系元素的穆斯堡尔效应已被14种元素观测到，其中大部分与Eu有关<151>。对于其它元素，存在技术上的困难：必须自制穆斯堡尔源，并在很低的温度下冷却源和样品。我们在核反应堆中用中子辐照的方法成功地制备了~ <155>Gd和~<166>艾德穆斯堡尔谱的窄线源，并测量了多种配合物、固溶体、金属间化合物和双氧化物在12 K下的穆斯堡尔谱。结果表明，四极耦合常数（e^2qQ）对^<155>Gd，有效磁场（H_<eff>）和自旋-自旋弛豫时间（τ）对^<166>艾德都是非常有用的参量，（1-x）ZrO_2-xGdO_3的e^2aQ值<1.5>在x = 0.18 × 0.50范围内随x的增大而增大，在x=0.5（火山岩结构）时达到最大值，然后在0.50&lt;x × 0.62范围内减小。由于e^2qQ反映了Gd核周围电荷分布的不对称性，因此在x=0.5的火成岩结构中，不对称性最大。发现<155>（1-x）ZrO_2-xGdO_2的^Gde^2qQ值<1.5>与<151>（1-y）ZrO_2-yEuO_2的^ Eu同分异构位移（δ）值平行变化<1.5>，这可以用M-O（M=Eu，Gd）键长的变化来解释<-1>.δ值按GdO_（6，7或8）&gt;&gt;GdN_2O_<6 or7>&gt;GdN_6O_2 ~* 的顺序减小，表明δ值随配位氮原子数目的增加而减小。弛豫时间的增加被认为是源于Er^&lt;3+&gt;自旋之间距离的延长。

The Moessbauer effect of lanthanoid elements have been observed 14 elements, most of which is concerned with ^<151>Eu. For the other elements there are technical difficulties : we must make Moessbauer source by our self and cool both the source and sample at very low temperature. However we have succeeded in making a good narrow line source for ^<155>Gd and ^<166>Ed Moessbauer spectroscopy by neutron irradiation in nuclear reactor.We have measured those Moessbauer spectra at 12K of many kinds of complexes, solid solution, inter metallic comaounds and double oxides. The results have shown that the quadrupole coupling constant (e^2qQ) is verv useful aarameter for ^<155>Gd, and the effective magnetic field (H_<eff>) and the spin-spin relaxation time (τ) for ^<166>Ed.The e^2aQ values of (1-x)ZrO_2-xGdO_<1.5> increases with the increase of x in the ranse 0.18≦x≦0.50, reach maximum at x=0.5 (pyroclore structure) and then decrease in the range 0.50<x≦0.62. Since e^2qQ reflects the asymmetry of the charge distribution around the Gd nucleus, the asymmetry has been found to be the largest in the pyroclore structure of x=0.5. The parallel change of ^<155>Gd e^2qQ values of (1-x)ZrO_2-xGdO_<1.5> with that of ^<151>Eu isomer shift (δ) values of (1-y) ZrO_2-y EuO_<1.5> is observed which will be explained by the change of the M-O (M=Eu, Gd) bond length.The δ values of β-diketonatosadolinium (III) complexes fall in the very narrow range of 0.54-0.65mms^<-1>. Furthermore δ decrease in the order GdO_<6,7 or 8>>GdN_2O_<6 or7>>GdN_6O_2*, suggesting that δ decrease with the increase in the number of the nitrogen atoms coordinated to Gd ions.The spin-spin relaxation times of the seven coordinated β-diketonatoaqua erbium (III) complexes have been found to increase with the increase in the bulkiness of the β-diketons from their ^<>166Er Moessbauer saectra. The increase in the relaxation times is considered to originate from the lengthening of the distances between the Er^<3+> spins.