Ethel C. Bucharsky

Lithium Diffusion Pathway in Li1.3Al0.3Ti1.7(PO4)3 (LATP) Superionic Conductor

The Al-substituted LiTi2(PO4)3 powders Li(1+x)Al(x)Ti(2-x)(PO4)3 (LATP) were successfully prepared by a water-based sol-gel process with subsequent calcination and sintering. The crystal structure of obtained samples was characterized at different temperatures using high-resolution synchrotron-based X-ray and neutron powder diffraction. Possible lithium diffusion pathways were initially evaluated using the difference bond-valence approach. Experimental 3D lithium diffusion pathway in LATP was extracted from the negative nuclear density maps reconstructed by the maximum entropy method. Evaluation of the energy landscape determining the lithium diffusion process in NASICON-type superionic conductor is shown for the first time.

Frequency dispersion of the ionic conductivity of RbAg4I5 at low temperatures

Abstract The ionic conductivity of the superionic conductor RbAg 4 I 5 was studied at low temperature using a modified electrochemical impedance spectroscopy (EIS) as well as dielectric measurements (DM). Experiments using RbAg 4 I 5 samples of constant crystal imperfection density were carried out in the temperature range 50 K≤ T ≤110 K and in the frequency range 10 1 Hz≤ f ≤10 7 Hz. The current data are in good agreement with previous low-frequency EIS measurements carried out in the frequency range 10 −3 Hz≤ f ≤10 5 Hz and high-frequency wave-guide measurements in the frequency range 18 GHz≤ f ≤40 GHz. The results confirm a nearly temperature-independent low-frequency ionic conductivity below a transition temperature T T t =(75±15) K which is caused by a change of the ion conduction mechanism. At T > T t , the ion transport occurs through grains and subgrains crossing grain and subgrain boundaries, whereas at T T t , the ion transport takes place only via crystal imperfections, i.e. along grain and subgrain boundaries. Finally, the new results presented feature a frequency dispersion of the ionic conductivity in the mid frequency range which follows a power law with an exponent of p =1±0.1, thus confirming the so-called ‘new universality’ law.