The compound AgI crystallizes, depending on temperature and pressure, with various crystal structures. While α-AgI is the stable form at elevated temperatures, the β and the γ forms exist at lower temperatures. Variants with stacking sequences different than in pure β-AgI and γ-AgI enrich the complex crystallographic situation for AgI. In the study presented here, we converted a mixture of β-AgI and γ-AgI into nanostructured γ-AgI by mechanical treatment, that is, by high-energy ball milling of such a mixture under ambient conditions. Our work extends an earlier study by Ahmad (Z. Naturforsch. 2015, 70b, 17). We used variable-temperature, potentiostatic conductivity spectroscopy as well as electric modulus measurements to characterize the electric transport parameters. For the case that the sample is heated to temperatures near and above 420 K, preliminary information on the “resistance” of the electric conductivity against healing of defects are also collected. As compared to the unmilled but mixed sample, whose Ag+ ionic transport is dominated by those ions residing in the γ-phase of AgI (0.25 eV vs. 0.46 eV in β-AgI), ball milling only leads to a small increase in overall electric conductivity (by a factor of 3–4) for nanocrystalline γ-AgI (0.25 eV). This observation is perfectly in line with a recent observation for the fast ion conductor Li10GeP2S12 (Hogrefe et al., J. Am. Chem. Soc. 2022, 144, 9597): In materials with already rapid diffusion pathways, nanostructuring and the introduction of defects and distortions do not lead to significantly enhanced ion transport. Here, a careful analysis of data from conductivity and modulus spectroscopy helps identify which dynamic parameters are mainly responsible for the change in the overall conductivity upon mechanical treatment of coarse-grained γ-AgI.

中文翻译：

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高能球磨制备纳米晶γ-AgI的离子电导率

根据温度和压力，化合物 AgI 会结晶，具有各种晶体结构。尽管α-AgI 是高温下的稳定形式，β和γ形式存在于较低温度下。堆叠顺序与纯版本不同的变体β-AgI和γ-AgI 丰富了 AgI 的复杂晶体学情况。在这里介绍的研究中，我们将以下物质的混合物转化为β-AgI和γ-AgI 转化为纳米结构γ-AgI通过机械处理，即通过在环境条件下对这种混合物进行高能球磨。我们的工作扩展了 Ahmad 的早期研究（Z. Naturforsch. 2015, 70b, 17）。我们使用变温、恒电位电导率光谱以及电模量测量来表征电传输参数。对于样品被加热到接近或高于 420 K 的温度的情况，还收集了关于电导率对缺陷愈合的“阻力”的初步信息。与未研磨但混合的样品相比，其 Ag+离子传输由驻留在其中的离子主导γAgI 的相（0.25 eV 与 0.46 eVβ-AgI），球磨仅导致纳米晶的整体电导率小幅增加（3-4 倍）γ-AgI（0.25 eV）。这一观察结果与最近对快离子导体 Li 的观察结果完全一致10GeP2S12（Hogrefe 等人，J. Am. Chem. Soc. 2022, 144, 9597）：在已经具有快速扩散路径的材料中，纳米结构以及缺陷和变形的引入不会导致离子传输显着增强。在这里，对电导率和模量光谱数据的仔细分析有助于确定哪些动态参数是粗粒机械处理后总体电导率变化的主要原因γ-AgI。