Planar Faults and Grain Boundary Precipitation in Non-Stoichiometric (Sr, Ca)TiO3 Ceramics

Abstract
Microstructures of non-stoichiometric-composition (Sr0.85Ca0.15O) x TiO2 ceramics (with x=0.98 and 1.02) were observed using high-resolution transmission electron microscopy and scanning transmission electron microscopy. Precipitation of Magnéli-phase was found at the grain boundary in the specimen for x=0.98, and Ruddlesden-Popper-type insertion layers in that for x=1.02. The crystallographic site occupancy of impurity atoms determined by ALCHEMI (Atom Location using CHanneling-Enhanced MIcroanalysis), showed that the excess TiO2 was precipitated as Magnéli phase in the specimen for x=0.98, and similarly that excess SrO formed insertion planar faults of NaCl type in that for x=1.02. No anti-site point defects were formed in either of the specimens.