High-temperature XRD investigations of phase transformation in mineralogy: examples for clay used in ceramics and phosphate minerals

High-temperature X-ray diffraction is a technique used to determine the mineralogy of a sample at various, non-ambient, temperatures. It allows the measurement and visualisation of dehydration and oxidation processes, phase transformations (Wahl et al., 1961; Montanari, 2004; Zamporti et al., 2012), reaction processes and crystallite growth (Natter et al., 2001). The approach was tested on two distinct materials, i.e. raw clays used for ceramic production and phosphate minerals. Four clay samples from Westerwald (Germany) were chosen: a Fe rich illite clay, a red, a yellow and a white clay. In addition, two natural phosphate samples were selected: alluaudite [Na2MnFe2+Fe3+(PO4)3] from Townsite, Pringle, South Dakota, USA (sample TOW-01; Hatert, 2002), and triphylite [LiFe2+(PO4)] from Palermo pegmatite, New Hamshire, USA. Mineral transformation and vitrification processes were followed from 30 to 1250°C