The distribution of grain boundary resistivities in SrTiO3 polycrystals: a comparison between spatially resolved and macroscopic measurements

Ohmic Ag/YBa 2 Cu 3 O 7-δ -microcontacts on adjacent grains of polycrystalline Fe-doped SrTiO 3 -samples have been used to investigate locally the properties of grain boundaries by means of impedance spectroscopy. Experiments at 30 different single grain boundaries permit reliable conclusions to be made on the distribution of grain boundary properties. For comparison conventional impedance measurements on a polycrystal were performed and a brick layer model was used to extract effective properties. The reasonable agreement between these effective parameters and the average of the locally obtained parameters demonstrates that, in this case, a brick layer analysis of conventional impedance experiments yields satisfactory estimates of the grain boundary properties.