Laboratory of mineralogical microanalysis (IIC). X-ray powder diffractometers (XRPD) are the key instruments of the laboratory. There are installed two PANalytical X’Pert MPD (Multi Purpose Diffractometer) X-ray powder diffractometers. The first is equipped with a cobalt X-ray tube and a fast linear position-sensitive detector X’Celerator. If necessary, in-situ installation of a high temperature chamber (Anton Paar HTK 16) or humidity controlled analysis (Anton Paar CHC + chamber) is possible. Bragg-Brentano reflection geometry can also be combined with micro-diffraction. This allows the analysis of small heterogeneous microsamples in a completely non-destructive manner, typically microsamples taken from works of art. In this geometry, two monocapillaries of different lengths with an output diameter of 0.1 mm are used. The second device is equipped with a copper X-ray tube and a PIXCel detector. In addition to analyses in conventional reflection geometry, it also allows samples to be analysed in transmission geometry. This is particularly advantageous in the case of more accurate determination of clay minerals (e.g. in earth pigments), where complementary analyses in reflection and transmission arrangements increase the accuracy of determination of these minerals and their polytypes. As supporting methods, the laboratory uses FTIR micro-spectroscopy (Bruker VERTEX spectrometer and Hyperion FTIR microscope equipped with wide band MCT detector and Focal Plain Array – FPA detector for chemical imaging), scanning electron microscopes with EDS and WDS detectors (SEM Jeol JSM-6510, HRSEM FEI NanoSEM 450), thermal analysis (TA/MS, SETARAM) and other methods available in the ALMA framework (e.g. large area MA-XRF scanner, etc.). As a result, it provides a very comprehensive and advanced mineralogical analysis at the microscale. XRPD has a long tradition in the ALMA Laboratory. ALMA was involved in testing, and was one of the first laboratories in the field of cultural heritage research to start using laboratory X-ray powder micro-diffraction (micro-XRPD), which enables analysis of heterogeneous fragments of paints or their cross-sections without any pre-treatment. Despite its lower spatial resolution and longer measuring times, it proved to be – in many cases – more efficient and reliable for identifying crystalline phases in paint layers than the widely-used Raman micro-spectroscopy. The field of application of micro-XRPD is very wide – it has an irreplaceable role in the provenance analysis of mineral pigments, diagnostics of the method of their preparation and also in the study of their degradation, salt corrosion, thermal transformation, etc. and can be applied to various materials in fine and applied art (pigments, stones, metals, ceramics etc.). Recently, the method has also been adapted for the measurement of small paintings (miniatures), which is a completely new way of its application.
Recent Comments