We have carried out time-domain electrostatic force spectroscopy on two different ion conducting glasses using an atomic force microscope. We compare the electrostatic force spectroscopic data obtained at different temperatures with macroscopic electrical data of the glasses. The overall consistency of the data shows that electrostatic force spectroscopy is capable of probing the ion dynamics and transport in nanoscopic subvolumes of the samples.Ion conducting crystals, glasses and polymers are widely used as solid electrolytes in batteries, fuel cells, and chemical sensors. A lot of research work is being carried out in order to find new materials with improved ionic conductivities. One method that is becoming more and more technologically relevant is nanostructuring of materials. It has, for instance, been found that the ionic conductivity of nanocrystalline ionic conductors can be increased by adding nanocrystalline insulators [1]. In the case of glasses, a conductivity enhancement can be achieved by the formation of nanocrystallites during partial crystallisation [2]. Furthermore, the ionic conductivity of polymer electrolytes can be improved considerably by incorporating nanoparticles, such as Al 2 O 3 , TiO 2 and ZrO 2 , into the polymer matrix [3].Up to now, there is no general agreement about the origin of these conductivity enhancement effects. A limiting factor hindering a better theoretical understanding and thus a more systematic preparation of improved materials is the traditional characterization of the ion dynamics by means of macroscopic techniques, such as conductivity spectroscopy, tracer diffusion measurements, and NMR relaxation techniques. In nanostructured solid electrolytes, diffusion pathways in different phases and at interfaces are believed to play an important role for the ion transport [1,4]. Therefore, an experimental method capable of probing ion transport on nanometer length scales would be highly desirable.In principle, electrostatic force microscopy and spectroscopy techniques using an atomic force microscope (AFM) are well suited for this purpose. Such techniques have been applied in different research fields to characterize the electrical properties of materials on nanoscopic length scales. Scanning capacitance microscopy [5,6,7] and scanning kelvin probe microscopy [8,9] have been applied to semiconductors and semiconductor devices. The electrical properties of nanostructured materials adsorbed on insulating substrates, e.g. carbon nanotubes and DNA molecules adsorbed on silica, have been studied by using electrostatic force microscopy techniques [10,11]. Israeloff and coworkers used timedomain electrostatic force spectroscopy in order to characterize dielectric fluctuations in thin polymer films at the glass transition [12,13,14].In this letter, we report, for the first time, on the application of electrostatic force spectroscopy for studying ion transport in solid electrolytes. To do this, we chose two ion conducting glasses with well-known macroscopic electrical properties....

The hopping movements of mobile ions in a nanostructured LiAlSiO4 glass ceramic are characterized by time-domain electrostatic force spectroscopy (TDEFS). While the macroscopic conductivity spectra are governed by a single activation energy, the nanoscopic TDEFS measurements reveal three different dynamic processes with distinct activation energies. Apart from the ion transport processes in the glassy and crystalline phases, we identify a third process with a very low activation energy, which is assigned to ionic movements at the interfaces between the crystallites and glassy phase. Such interfacial processes are believed to play a key role for obtaining high ionic conductivities in nanostructured solid electrolytes.

We use time-domain electrostatic force spectroscopy (TD-EFS) for characterising the dynamics of mobile ions in a partially crystallised LiAlSiO 4 glass ceramic, and we compare the results of the TD-EFS measurements to macroscopic electrical conductivity measurements. While the macroscopic conductivity spectra are determined by a single dynamic process with an activation energy of 0.72 eV, the TD-EFS measurements provide information about two distinct relaxation processes with different activation energies. Our results indicate that the faster process is due to ionic movements in the glassy phase and at the glass-crystal interfaces, while the slower process is caused by ionic movements in the crystallites. The spatially varying electrical relaxation strengths of the fast and of the slow process provide information about the nano-and mesoscale structure of the glass ceramic.