The following hypothesis can be formulated based on TG/DTA curves: CaCO3 first reacts with ZrO2 at about 650 °C forming CaZrO3. This is followed by further decomposition of CaCO3 and the formation of CaZrO3 and some CaTiO3. Early BaZrO3 formation might also take place in parallel starting at 650 °C, even before the endothermic transition of the BaCO3 crystal structure. The second carbonate decomposition in the BCZT mixture at about 750 °C strongly resembles that of BaCO3 in the BaTiO3 system. While TG/DTA provides an overview of the types of reactions taking place, it lacks information about the exact phase composition at individual temperatures.