Thermal decomposition mechanism of triple carbonate (Ba,Sr,Ca)CO ₃

The thermal decomposition mechanism of the triple carbonate (Ba,Sr,Ca)CO3 is shown to proceed in a single step from the carbonates to the corresponding oxides under the condition where the decomposition itself is rate limiting. When the decomposition occurs under a high local CO2 pressure, it appears to proceed in two steps due to a subsequent recombination reaction between the CO2 and the oxides. The carbonates initially decompose into an x-ray amorphous oxide which upon further heat treatment yields a solid solution oxide (Ba,Sr,Ca)O. The exact nature of this x-ray amorphous oxide is uncertain but hydration experiments support it being either a microcrystalline or structurally disordered solid solution.