# Synchrotron X-ray Microprobes: An Application on Ancient Ceramics
###### Abstract
It is non-invasive and non-destructive on the micro-samples, which can be later on used for further investigations. SR X-ray sources offer numerous advantages. They are brilliant sources assuring intense X-ray radiation, providing a quasi-monochromatic beam and an energy selection over a wide range, which can be chosen according to elements of interest [17,18]. In the last decades, one of the main innovations at SR-based X-ray sources are micro- and nano-focusing systems aimed at obtaining micro- and nanometric lateral resolution for both qualitative and quantitative analysis in complex and/or tiny samples [19, 20, 21]. Soft and hard X-ray microprobes are available at synchrotron radiation sources. The selection of the probes depends on the energy range of interest--and thus the elements to detect. In ceramic studies, elements with emission energies below 10 keV are common constituents. However, the use of harder X-ray microprobes appears suitable for the determination of elements usually present in traces and also relevant in provenance or technological studies. Among SR-based X-ray microbeam techniques, \(\upmu\)XRF mapping systems appear particularly useful in analyzing ceramic decorations (slip, glazes, etc.) or to detect enrichment/depletion of specific elements across ceramic section for provenance or technological purposes [22,23]. Being heterogenous materials, the analysis of ceramics can benefit from the combination of different SR-based X-ray methods with micrometric or sub-micrometric spatial resolutions. For example, \(\upmu\)XRF can be combined with micro-X-ray diffraction (\(\upmu\)XRD) for the determination of crystalline phases in both the ceramic body and decorative layers or nano-XRD for single crystal studies even in not-crystalline matrix, such as in glazes [24, 25, 26]. \(\upmu\)XRF can be also coupled with \(\upmu\)- or nano-XANES, enabling the determination and even the distribution of the valence state of an element [27]. Usually, this method requires the preliminary acquisition of a \(\upmu\)XRF map for the selection of areas of interest. The XANES measurement consists of scans in fluorescence or transmission (TXM) mode--depending on sample preparation and characteristics--at defined energies across the adsorption edge of the element of interest. \(\upmu\)- and nano-XANES are still relatively recent application in the CH field and therefore poorly explored [20]. In literature, very few examples discuss the merits of \(\upmu\)XANES in the mild or hard X-ray range, particularly suitable for technological studies on slips and gloss layers in decorated vessels [28, 29, 30]. The combination of SR-based X-ray methods, such as fluorescence, diffraction and absorption, appears relevant for different purposes in ancient ceramics studies. For provenance issues, SR-based \(\upmu\)XRF mapping might provide insights on the chemical distribution of elements across the sample section. It can highlight enrichment/depletion of minor and trace elements in ceramic paste vs. surface decoration, also in comparison with other productions and/or reference data. Additionally, SR-based X-ray methods are suited for technological studies. The microanalysis of slip or varnished surfaces might provide information on chemical composition, elemental distribution, presence of crystallites in glossy matrix and speciation of elements (metals) for the better understanding of manufacture procedures. For such applications, the sampling of small fragments or even a more refined sample preparation (e.g., cross-section or thin section) depends on the field of view required in the investigation. XRF or XANES maps acquired with upbeams in fluorescence mode can be carried out on small fragments. The sample can be positioned in cross-sectional geometry to acquire information on both the clay paste and the surface slip.