Experimental evidence for space charge segregation in Nb-doped BaTiO3

There is ample experimental evidence demonstrating space charge segregation in acceptor-doped BaTiO3. However there is still some controversy regardin g donor-doped BaTiO3. Considering the space charge segregation theory in Ba TiO3, the calculated driving force for space charge segregation is larger i n acceptor-doped cases than in donor-doped cases. This result explains why acceptor segregation can be easily detected. However, a significant concent ration of donors can also cause donor segregation. In donor and acceptor co doped BaTiO3, the grain sizes are very small, and donor segregation can be detected for compositions inducing a large space charge potential. In addit ion, in compositions that induced a small space charge potential, the grain sizes are very large, and donor segregation is not detected, although the total doping concentration is larger. This phenomenon means that donor segr egation is caused by the space charge potential rather than misfit strain e nergy.