Application of focused ion beam-field emission scanning electron microscopy-X-ray microanalysis in the study of the surface alterations of archaeological tin-glazed ceramics

Abstract

[EN] The historical evolution of tin-glazed ceramics is a subject that has attracted the attention of many scientists and, consequently, abundant archaeometrical studies can be found in the specialized literature. Nevertheless, a lesser number of studies aimed at the characterization of the alterations undergone by archaeological glazes has been reported. This work describes some unusual alteration processes found in tin-glazes depending on the environmental conditions surrounding the piece during centuries. For this purpose, focused ion beam-field emission scanning electron microscopy-X-ray microanalysis (FIB-FESEM-EDX), an advanced instrumental technique for surface analysis at the nanoscale, has been used for the first time, complementarily to optical microscopy (OM), FESEM-EDX and Fourier transform Infrared spectroscopy (FTIR). In the buried glaze the nanostructure of the outer lamellar corrosion layer due to humidity-dryness cycles is described. Unusual and selective erosion of the glaze matrix due to the silicification metabolism of diatoms is observed in a submarine glaze. A nanometric outer corrosion layer formed by precipitated corrosion products and unspecific organic matter that has been partially degraded to lead and calcium oxalates is found in a glazed tile subjected to an atmospheric environment.