The Similar Defect Chemistry of Highly-Doped SrBi2Ta2O9 and SrBi2Nb2O9

The equilibrium electrical conductivities of undoped SrBi^sub 2^Ta^sub 2^O^sub 9^ (SBT) and SrBi^sub 2^Nb^sub 2^O^sub 9^ (SBN) have been shown to behave quite differently. SBT has the behavior expected for a 1% acceptor-doped oxide, while SBN behaves like a 1% donor-doped oxide. This difference has been related to the substantial cation place exchange that occurs between the Bi^sup + 3^ and Sr^sup + 2^ ions in the alternating layers of the structure. It was proposed that this place exchange is not entirely self-compensating, as would be expected for a simple, isotropic oxide, but that there is some local compensation within each layer by lattice and/or electronic defects. It is now shown that the equilibrium conductivity of 3% donor-doped SBT is similar to that of undoped SBN, while the equilibrium conductivity of 3% acceptor-doped SBN resembles that of undoped SBT. Thus the defect chemistrys of the two compounds are quite similar, but the equilibrium conductivities are displaced along a doping axis.[PUBLICATION ABSTRACT]