The frequency-dependent alternating current conductivity of nanocrystalline material was measured by means of impedance spectroscopy (5Hz to 13MHz, 390 to 500K). It was found that the real part of the conductivity at low frequencies was more than 4 orders of magnitude greater than the direct current value for monocrystalline material. Also, the activation energy was less than one third of that for intrinsic conductivity in monocrystalline material. It was concluded that this indicated that there was an increased mobility of P-ions in the interfacial regions. The complex impedance spectra before and after annealing were explained in terms of ion dynamics in grains and interfaces.

W.Puin, P.Heitjans: Nanostructured Materials, 1995, 6[5-8], 885-8