Abstract
ABSTRACTMeasurements of the equilibrium electrical conductivity of Ca-doped BaTiO3indicate a highly acceptor-doped behavior when y > 1 in the general formula (Ba1−xCaxO)yTiO2. It has been suggested that when there is an excess of alkaline earth oxides, some Ca++occupies Ti-sites, where it acts as a doubly charged acceptor, CaTi''. This possibility has been checked with a recently developed technique for determining the crystallographic site occupancy of impurity atoms. Known as ALCHEMI (Atom Location Using Channeling-Enhanced Microanalysis), the technique relies on the dependence of the characteristic X-ray emission on the incident electron beam direction. A significant channeling effect was observed for slightly positive and negative excitations of the [100] reflection. The results indicate that for the composition (Ba0,85Ca0.15O)1.02TiO2.00, a substantial fraction of the total calcium (> 20%) occupies Ti sites.
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