ABSTRACT Hexagonal neo-formed crystallites have been observed in thin section of different medieval and post-medieval lead-glazed ceramics. Although they are clearly visible in thin section using plane polarized light, their plate shape makes them barely seen on the polished cross sections. Basal sections have never been found on the polished sections and only few transversal very thin sections could be seen. In this case, the morphology resembles acicular and it is not possible to analyze them properly by SEM–EDX because the crystals are very thin and the glaze surrounding is analyzed as well. Micro-Raman microscopy was carried out directly on the polished thin sections. This technique allows specific areas as small as 1 μm in diameter to be analyzed and it is able to characterize inclusions that are not found on the glaze surface. However, the wavenumber features observed cannot be assigned to a specific compound. The thickness of the crystallites (a few hundred nanometers) seems to be responsible for the low sensitivity of the Raman instrumentation. 15 × 15 μm2 micro-X-ray diffraction patterns using synchrotron radiation (SR-μXRD) in transmission geometry were obtained from the crystals using the same thin section preparation. SR-μXRD was able to localize the crystallites and avoid the overlapping signals corresponding to other mineral phases. In this way, the hexagonal crystallites present in the glaze have been unambiguously identified as hematite crystallites. Finally, some replications were made under laboratory-controlled conditions to determine the firing conditions in the formation of those crystallites. The presence of hematite coexisting with melanotekite indicates a firing temperature <925°C, while the presence of only hematite suggests a firing temperature >925°C

中文翻译：

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陶瓷铅釉中新形成的赤铁矿晶体的技术意义

摘要在不同的中世纪和中世纪铅釉陶瓷的薄层中已观察到六方新形成的微晶。尽管它们在平面偏振光的作用下在薄片中清晰可见，但其板状形状使得它们在抛光的横截面上几乎看不到。从来没有在抛光过的部分上找到基底部分，只能看到很少的横向非常薄的部分。在这种情况下，形态类似于针状，并且由于晶体非常薄并且还分析了周围的釉料，因此无法通过SEM-EDX对其进行适当分析。直接在抛光的薄切片上进行显微拉曼显微镜检查。该技术可以分析直径小至1μm的特定区域，并且能够表征釉面未发现的夹杂物。然而，观察到的波数特征无法分配给特定化合物。微晶的厚度（几百纳米）似乎是拉曼仪器灵敏度低的原因。使用相同的薄切片制备方法，从晶体中获得了使用同步辐射（SR-μXRD）的15×15μm2微X射线衍射图，其透射几何形状。SR-XRD能够定位微晶，并避免了与其他矿物相相对应的重叠信号。通过这种方式，釉中存在的六角形微晶被明确地识别为赤铁矿微晶。最后，在实验室控制的条件下进行一些复制，以确定那些微晶形成中的烧成条件。