Abstract
The metastable phase, named δ-phase, of SrCO3 or BaCO3 is able to obtained by a rapid quenching for a mixed powder with 10 mol% of BaSO4 from the phase transition temperature of the host carbonates.
The study was carried out to clarify the formation mechanism of those δ-phases using DTA and high temperature X-ray diffractometer.
The results obtained are summarized as follows;
1) Mutual substitution between CO3 and SO4 ions was accelerated around the phase transition temperature of the carbonate.
2) It was identified the the stable phase above the transition temperature was not δ-but α-phase (hexagonal) incorporated with BaSO4.
The result suggests that the δ-phase is formed at the quenching process which brings about a lattice shrinkage to prevent the reversible transition.
