Grain boundary barrier breakdown in niobium donor doped strontium titanateusing in situ electron holography

The electrical activity of numerous electroceramics originates with space c harge potential across internal interfaces. Space charge formation and the resultant potential barrier at interfaces are believed to be responsible fo r many interesting and useful properties of electroceramics, ranging from n onlinear current-voltage characteristics to enhanced dielectric properties. Direct current electrical measurements of individual grain boundaries in N b donor doped SrTiO3 bicrystals reveal a highly resistive and nonlinear beh avior compared to single crystals. The origin of this nonlinear resistance has been examined with electron holography, observing both static and dynam ic attributes of the internal potential. In the static case with no applied current, the grain boundary potential barrier height was measured to be ab out 0.45 V. During the application of a high current, this potential barrie r was suppressed, presenting the first direct real space evidence for break down of an internal grain boundary barrier. (C) 1999 American Institute of Physics. [S0003-6951(99)04704-X].