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- 2025 (2)
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- Englisch (2)
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- Mineral thermometry (2)
- Raman spectroscopy (2)
- Dolomite (1)
- High-fired gypsum mortar (1)
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This paper suggests the use of high‐resolution Raman scattering bands of MgCa carbonates as posteriori thermometer minerals in archaeometric studies. Therefore, the thermal behavior of two dolomite samples and the hydration and carbonation reaction in air of the decomposition products were investigated by Raman microspectroscopy. The increase in the calcination temperature resulted in the formation of – Raman silent MgO and – inert Mg calcite at 700°C–750°C. In contrast, the decarbonation, hydration, and recarbonation of sample material exposed to 750°C–900°C in a muffle furnace led to the appearance of Mg‐free calcite. High spectral resolution Raman spectroscopy enabled a spectral distinction between these two groups due to differences in the band parameters (peak position, bandwidth) of the vibrational (v1, v4, L) modes of calcite. In combination with Raman microspectroscopic mapping, this spectral information represents a new approach for the estimation of burning temperatures of medieval high‐fired gypsum mortars via natural dolomite impurities. Thus, the results of this work highlight the importance and potential of Raman microspectroscopy as a thermometric tool for elucidating the thermal history of anthropogenic fired materials, with potential applications for archaeometry and art technology, as well as for quality controls in the frame of the production of mineral mortar binders and ceramics or bricks, respectively.
The reconstruction of the thermal history of anthropogenic materials is crucial for understanding historical manufacturing techniques. Preparatory parameters such as firing temperature, heating and cooling rates, soaking time, and kiln atmosphere significantly affect the chemical and structural properties of the final product. Comparing historical materials with replicas produced under well-defined laboratory conditions helps identify indicators for these parameters. This comparative approach is greatly enhanced by spectroscopic analyses. Raman spectroscopy has proven to be a powerful tool in this field due to its high sensitivity to crystal-chemical alterations and high spatial resolution.
The results of thermal experiments with gypsum and carbonate raw materials at burning temperatures up to 1000 °C are presented. Precise measurements of Raman peak positions and Raman band widths enable the differentiation of chemically similar phases. Changes in the Raman band parameters are evident even after the subsequent hydration-hardening process of the fired samples, allowing the spectral discrimination of samples treated at different temperatures steps. These findings from the thermal experiments are further applied to Raman micro-spectroscopic mappings of medieval and reenacted mortars. The extracted Raman band parameters show comparable values between the experimental and real-life samples, proving Raman spectroscopy as a suitable tool for estimating the burning temperature and thus elucidating the manufacturing procedures of anthropogenic materials.
