Universal trend of the Haven ratio in glasses: origin and structural evidences from neutron diffraction and small-angle neutron scattering
Universal trend of the Haven ratio in glasses: origin and structural evidences from neutron diffraction and small-angle neutron scattering
复制标题
玻璃中哈文比的普遍趋势：中子衍射和小角中子散射的起源和结构证据
DOI：
10.1016/s0022-3093(01)00673-1
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发表时间：
2001
影响因子：
3.5
通讯作者：
A. Lapp
中科院分区：
文献类型：
--
作者：
E. Bychkov;D. Price;A. Lapp
Haven比HR在氧化物和硫属化物玻璃体系中表现出作为移动的离子含量x的函数的普遍趋势。在极稀玻璃（x=30-100 ppm M+）中的离子输运是不相关的（HR <1），但HR随x的增加而迅速下降，并在x <10 at.%时几乎保持不变（HR=0.2-0.4）。缺乏对这种现象的实验验证解释。我们对许多银硫属玻璃体系进行的中子衍射（ND）和小角中子散射实验表明，这一普遍趋势的结构起源是在4个数量级的Q范围内进行的，从3×10− 3到40 A −1。玻璃从临界逾渗域（xc = xc = 1- 3at.%）Ag，其中xc = 30 ppm Ag是逾渗阈值）的特征在于无规银分布。在该区域中，平均Ag-Ag分离距离随着x的增加而减小，导致电子相互作用的增加，从而导致HR的单调减小。Ag）的特征在于非随机的Ag分布。边缘共享的AgX 3金字塔（X=S，Se）形成链、交联链、片、隧道等，并提供优先传导路径。然而，电子相互作用由不变的Ag-Ag第二近邻距离控制，因此Haven比基本上保持恒定。
The Haven ratio HRexhibits a universal trend in oxide and chalcogenide glassy systems as a function of the mobile ion content x. The ion transport in extremely dilute glasses (x=30–100 ppm M+) is uncorrelated (HR≈1), but HRdecreases rapidly with increasing x and remains nearly constant (HR=0.2–0.4) at x ⩾ 10 at.%. An experimentally verified interpretation of this phenomenon is lacking. Our neutron diffraction (ND) and small-angle neutron scattering experiments carried out over a Q-range of four orders of magnitude, from 3×10−3to 40 A ̊−1, for a number of silver chalcogenide glassy systems suggest a structural origin for this universal trend. Glasses from the critical percolation domain (xc⩽ x ⩽ 1–3 at.% Ag, where xc≈30 ppm Ag is the percolation threshold) are characterised by a random silver distribution. The average Ag–Ag separation distance decreases with increasing x in this domain, leading to an increase in the interionic interactions and thus to a monotonic decrease of HR. In contrast, glasses from the modifier-controlled domain (x ⩾ 10 at.% Ag) are characterised by a non-random Ag distribution. Edge-shared AgX3pyramids (X=S, Se) form chains, cross-linking chains, sheets, tunnels, etc., depending on the system, and provide preferential conduction pathways. The interionic interactions, however, are controlled by an invariant Ag–Ag second neighbour distance of ≈3 Å, and so the Haven ratio remains essentially constant.