GRAIN-BOUNDARY MOBILITY OF BATIO3 DOPED WITH ALIOVALENT CATIONS

The effect of three aliovalent cations, Nb5+, La3+ and Co2+, on the gr ain 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 concentrati ons of up to 1.25 atomic per cent (at%). For the donor cation Nb5+, th e boundary mobility initially increased with cation concentration but then decreased markedly above a doping threshold of 0.3-0.5 at%. The b oundary mobility of the BaTiO3 doped with the acceptor cation Co2+ dec reased monotonically with dopant concentration. Ata cation concentrati on of 0.75 at%, the boundary mobility was reduced by a factor of appro ximately 25, 10 and 50 times by Nb5+, La3+ and Co2+ respectively. A ma jor role of the dopants is seen to be their ability to influence the b oundary mobility. The effects of the dopants on the boundary mobility are discussed in terms of the defect chemistry and the space-charge co ncept. (C) 1998 Published by Elsevier Science Limited. All rights rese rved.