In this temperature range, the transformation from α-BaCO3 to β-BaCO3 takes place, as predicted by the DTA (Figure ) and reported in the literature . This transformation also coincides with the start of the BaTiO3 formation reaction . The small diffraction peaks of CaTiO3 observed at lower temperatures become indistinguishable from the background in this range. It cannot be determined, whether the phase is partially dissolved in the newly-formed BaTiO3 or if it participates in the formation of an intermediate phase. A small amount of a low-crystallinity perovskite-type phase was also detected at 800 °C and above. Although at this point the exact composition is unclear and fluctuates largely over the temperature range, its unit cell size indicates a BaZrO3-rich phase.