Grain boundary mobility of BaTiO3 doped with aliovalent cations

The effect of three aliovalent cations, Nb5+, La3+ and Co2+, on the grain growth kinetics of nearly fully dense BaTiO3 (Ba/Ti atomic ratio=1.001) was measured in O-2 at 1300 degrees C and for dopant concentrations of up to 1.25 atomic per cent (at%). For the donor cation Nb5+, the boundary mobility initially increased with cation concentration but then decreased markedly above a doping threshold of 0.3-0.5 at%. The boundary mobility of the BaTiO3 doped with the acceptor cation Co2+ decreased monotonically with dopant concentration. Ata cation concentration of 0.75 at%, the boundary mobility was reduced by a factor of approximately 25, 10 and 50 times by Nb5+, La3+ and Co2+ respectively. A major role of the dopants is seen to be their ability to influence the boundary mobility. The effects of the dopants on the boundary mobility are discussed in terms of the defect chemistry and the space-charge concept. (C) 1998 Published by Elsevier Science Limited. All rights reserved.