Abstract The crystallization of iron-containing sodium silicate phases holds particular importance, both in the management of high-level nuclear wastes and in geosciences. Here, we study three as-quenched glasses and their heat-treated chemical analogs, NaFeSiO4, NaFeSi2O6, and NaFeSi3O8 (with nominal stoichiometries from feldspathoid, pyroxene, and feldspar mineral groups, i.e., Si/Fe = 1, 2, and 3, respectively) using various techniques. Phase analyses revealed that as-quenched NaFeSiO4 could not accommodate all Fe in the glass phase (some Fe crystallizes as Fe3O4), whereas as-quenched NaFeSi2O6 and NaFeSi3O8 form amorphous glasses. NaFeSi2O6 glass is the only composition that crystallizes into its respective isochemical crystalline polymorph, i.e., aegirine, upon isothermal heat-treatment. As revealed by Mössbauer spectroscopy, iron is predominantly present as fourfold-coordinated Fe3+ in all glasses, though it is present as sixfold-coordinated Fe3+ in the aegirine crystals (NaFeSi2O6), as expected from crystallography. Thus, Na-Fe silicate can form a crystalline phase in which it is octahedrally coordinated, even though it is mostly tetrahedrally coordinated in the parent glasses. Thermal behavior, magnetic properties, iron redox state (including Fe K-edge X‑ray absorption), and vibrational properties (Raman spectra) of the above compositions are discussed.

中文翻译：

---

NaFeSiO4、NaFeSi2O6 和 NaFeSi3O8 玻璃和微晶玻璃的结构

摘要 含铁硅酸钠相的结晶在高放核废料的管理和地球科学中都具有特别重要的意义。在这里，我们研究了三种淬火玻璃及其热处理后的化学类似物 NaFeSiO4、NaFeSi2O6 和 NaFeSi3O8（具有来自长石、辉石和长石矿物群的标称化学计量，即 Si/Fe = 1、2 和 3，分别）使用各种技术。相分析表明，淬火状态的 NaFeSiO4 不能容纳玻璃相中的所有 Fe（一些 Fe 结晶为 Fe3O4），而淬火状态的 NaFeSi2O6 和 NaFeSi3O8 形成非晶玻璃。NaFeSi2O6 玻璃是唯一一种在等温热处理后结晶成其各自的等化学结晶多晶型物，即 aegirine 的组合物。正如穆斯堡尔光谱所揭示的那样，铁在所有玻璃中主要以四重配位的 Fe3+ 形式存在，尽管它在 aegirine 晶体 (NaFeSi2O6) 中以六重配位的 Fe3+ 形式存在，正如晶体学所预期的那样。因此，Na-Fe 硅酸盐可以形成八面体配位的结晶相，即使它在母体玻璃中大部分是四面体配位的。讨论了上述组合物的热行为、磁性、铁氧化还原状态（包括 Fe K 边 X 射线吸收）和振动特性（拉曼光谱）。尽管它在母眼镜中主要是四面体协调的。讨论了上述组合物的热行为、磁性、铁氧化还原状态（包括 Fe K 边 X 射线吸收）和振动特性（拉曼光谱）。尽管它在母眼镜中主要是四面体协调的。讨论了上述组合物的热行为、磁性、铁氧化还原状态（包括 Fe K 边 X 射线吸收）和振动特性（拉曼光谱）。