Liquid phase behaviour in nonstoichiometric calcium-doped lanthanum chromites

The sinterability of (La,Ca)CrO3 is analysed by comparing the liquid phase behaviour in A-site excess and A-site deficient compositions (referring to the ABO(3) formula). The analysis shows that a series of A-site excess and deficient compositions form distinct liquid phases belonging to the CaO-Cr2O3 phase system. Although both series experience grain growth and densification due to the presence of a liquid phase, the A-site excess compositions exhibit greater shrinkage and sinter to closed porosity, whereas the A-site deficient compositions remain porous. During the final stages of sintering, surplus liquid from the A-site excess material exudes to the free-surface forming a layer of uniform thickness. By comparison, the liquid in the A-site deficient composition segregates to the free-surface forming islands and leaving porous regions in the bulk matrix. It is concluded that the different liquid phase compositions in the A-site excess and A-site deficient (La,Ca)CrO3 have dissimilar wetting characteristics during the later stages of sintering. The A-site deficient liquid forms a premature solid phase, which accounts for the difference in sintering behaviour.